Magnesium Oxide Delivers More Magnesium with Fewer Pills

Updated: March 20, 2023

Magnesium Oxide capsules zoomed in

It’s true that magnesium oxide is less soluble than several other forms of supplemental magnesium.

However, magnesium oxide is at least as effective (if not better) at restoring and maintaining a healthy level of magnesium in your cells and bones.

How is this possible? I’ll explain!

But before I do, we need to understand how magnesium is absorbed.

In all its natural forms, magnesium is bound to another chemical compound, for example: carbonate; gluconate; citrate; lactate; aspartate; or oxide. The combinations of magnesium and one of these compounds are called magnesium salts.

When you consume any magnesium salt, the magnesium must be freed from its partner compound during digestion and made soluble (ionized). Once it is made soluble, your body can absorb the magnesium.

For this to happen effectively, stomach acid has to be present. So it’s also helpful to remember that:

  1. It’s best to take your supplements with a meal because your stomach responds to your consumption of food by secreting stomach acid.
  2. Medications that prevent stomach acid production impair your ability to digest and absorb minerals – and virtually all other nutrients.

Why Magnesium Oxide Provides More Elemental Magnesium

It’s true that magnesium oxide is not as easy to render soluble as some other magnesium salts. It’s therefore not absorbed as rapidly as other forms of magnesium, e.g. magnesium citrate, gluconate, lactate, aspartate.

But although magnesium oxide has a lower rate of absorption it contains a MUCH greater amount of actual magnesium to begin with. More than what is provided by other magnesium salts.

Therefore, even with the lower rate of absorption, magnesium oxide still delivers more magnesium per tablet. So more magnesium gets into your bloodstream to deliver all its many benefits to your bones and body!

This is illustrated in the table Comparison of Magnesium Salts below: 1-2

Comparison of Magnesium Salts
MG Salt % Elemental MG % Elemental MG Absorbed Mg’s of Elemental MG Absorbed per 100 mg of MG Salt
Oxide 60% 23%* 13.8
Carbonate 28% ~20% ** ~5.2
Chloride 26% 20% 5.2
L-lactate 12% 42% 5
Citrate 11% 30% 3.3
Aspartate 8% 42% 3.3
Glycinate 14% 23% 3.2
Gluconate 6% 19% 1.14

*On the web, you’ll see many sites claiming that only 4% of the magnesium in magnesium oxide is absorbed. This claim is based upon a small study by Firoz et al. (2001), which is discussed fully below. The actual data in this study shows something very different. The stated percentage of elemental magnesium absorbed from magnesium oxide in the above table — 23% — is the statistic provided in a review and meta-analysis of numerous studies by Ranade et al., (2001), cited below.

**Magnesium carbonate is nearly insoluble, but in the presence of stomach acid (HCl), magnesium carbonate is converted into magnesium chloride, which allows 20% of elemental magnesium to be absorbed.

As you can see, magnesium oxide contains the most elemental magnesium of 60%. And 23% of this can be absorbed.

Magnesium citrate, for example, contains only 11% elemental magnesium. And only 30% of this is absorbed.

So the percentage of elemental magnesium to begin with is just as important as the rate of absorption.

What Does This Mean For You, In Practical Terms?

You can get comparable or better health benefits with magnesium oxide. And you’ll also require fewer capsules, which will save you time and money.

The research most often cited to disparage magnesium oxide is a small study by Firoz et al. of 16 volunteers. The aim of this study was to test the claim that organic (chelated) magnesium salts (e.g., aspartate, lactate) are more easily absorbed than non-organic salts (e.g., oxide, chloride).3

The 16 volunteers were given four commercially-available magnesium salts: 2 organic (aspartate, lactate) and 2 non-organic (oxide, chloride), after which the amount of magnesium in their urine was checked. More magnesium excreted in the urine is thought to indicate that more magnesium has been absorbed; less magnesium excreted is thought to indicate that less magnesium has been absorbed. This rationale is based on the principle that the body works hard to maintain a steady state of magnesium balance, and in a steady state of magnesium balance, any extra magnesium absorbed will be excreted in the urine.

In this study, those taking magnesium oxide excreted less magnesium on average. So magnesium oxide was said to have a low fractional absorption rate of 4%. However, there are 2 important points not shared in this study:

  1. Half of the volunteers in this study excreted more or very comparable amounts of magnesium when taking magnesium oxide as they did when taking the other magnesium salts. Take a look for yourself at the table below – Urinary Magnesium, mg/day. The data in the following table is taken directly from Firoz M, et al’s 2001 article in Magnesium Research.

Averaging out the data produces a result that does not reflect what actually happened in the participants. Yet, what was reported is repeatedly cited on the internet. This is why I always read the full paper of any study I am going to rely upon for information.

     2. Most importantly, the key practical discovery made in this study was: “Magnesium excretion increased with all magnesium supplements.” What this means is that all the magnesium salts tested, including magnesium oxide, delivered more magnesium than was needed to meet the body’s magnesium balance requirement.

Urinary Magnesium, mg/day    
Study participant MG oxide MG chloride MG aspartate MG lactate Control 1* Control 2*
A 100 156 95 114 77 70
B 95 43 78 65 68 43
C 101 89 103 137 75 32
D 66 120 137 161 100 103
E 78 166 101 119 134 65
F 63 144 88 48 56 67
G 84 78 76 67 74 61
H 142 182 214 198 128 129
I 78 39 55 62 102 60
J 114 112 110 76 53 86
K 77 106 177 116 80 32
L 114 94 137 117 109 92
M 66 87 51 81 104 115
N 82 82 82 163 76 85
O 162 133 85 106 75 75
p 34 120 58 87 28 57

*Controls did not receive any supplemental magnesium.

Magnesium Oxide is Effectively Absorbed

Despite what you may have read on various websites, the peer-reviewed research on PubMed shows that magnesium oxide is effectively absorbed:

In a study involving 18 men, 24 hours after consumption of magnesium oxide supplements, magnesium levels in the urine increased about two times the normal amount. And, after 48 hours, magnesium levels had increased to roughly four times normal. The conclusion drawn by the researchers: these results clearly show that “magnesium oxide is effectively absorbed and elevates the biologically-active levels of magnesium in the bloodstream.” 4

It’s important to note here that magnesium oxide did not increase urinary excretion of magnesium within a couple of hours. This is an important point which I’ll explain below in “Higher bioavailability does not translate to more effective delivery to tissues.”

All forms of magnesium salts used in animal studies have been found to effectively restore magnesium levels in magnesium-depleted animals.

In one such study in 2005, rats were first given a magnesium-depleted diet and then provided with the same diet supplemented with 10 different magnesium salts: magnesium oxide, chloride, sulfate, carbonate, acetate, picolate, citrate, gluconate, lactate or aspartate. The results showed that while magnesium absorption values varied from 50% to 67%, all the magnesium salts used were equally efficient in restoring magnesium levels.5

The researchers also noted that “the quantity of magnesium in the digestive tract is the major factor controlling the amount of magnesium absorbed.” And as you now know, magnesium oxide contains a far greater amount of elemental magnesium than any of the other magnesium salts .5

A more recent animal study confirmed and strengthened these findings. In this one, for 5 weeks, rats were fed one of eight test diets supplemented with phytic acid (5 g/kg diet) and magnesium (155 mg elemental Mg/kg diet) from the following magnesium salts: magnesium oxide; magnesium sulfate; magnesium chloride; magnesium citrate; magnesium gluconate; magnesium orotate; and magnesium malate or EDTA magnesium salt.

The addition of phytic acid to the animals’ diet is important because phytic acid binds strongly to minerals and forms an insoluble complex. This means less of the minerals consumed can be absorbed. Despite the addition of phytic acid to the animals’ diet, all the magnesium salts tested were found to be comparably bioavailable: “The results indicate that any differences in the magnesium bioavailability of the compounds were small and physiologically irrelevant.” 6

woman put effervescent tablet in glass

Higher Bioavailability Does Not Necessarily Translate to More Effective Delivery to Tissues

When a magnesium supplement is highly bioavailable, it will be rapidly absorbed from the small intestine into the bloodstream, and magnesium blood levels will quickly rise. This sounds good, but when blood magnesium levels exceed a critical threshold, the excess is rapidly excreted by the kidneys. The end result is a shorter duration of magnesium availability to tissues. Magnesium salts with the greatest water solubility, bioavailability and rate of absorption are also more rapidly excreted in urine.

The lower parts of the small intestine are the primary sites of magnesium absorption. However, magnesium is also absorbed throughout the entire intestinal tract. Magnesium does not have special carriers that pull it into the bloodstream. Its absorption is a passive transcellular process.

For this kind of absorption process, the quantity of magnesium that passes through the digestive tract is the major factor controlling the amount of magnesium that is absorbed.

Because magnesium oxide contains more elemental magnesium and is less soluble, it’s absorbed into the bloodstream more slowly as it passes through the digestive tract. It will not raise blood levels excessively, and will therefore not be rapidly excreted. 5,7.8

The Research-Backed Bottom Line on Magnesium Oxide

You can get the same benefits from magnesium oxide with fewer pills. Magnesium oxide is the most effective magnesium supplement – and that is why it was selected for use in AlgaeCal Plus.


What is the best form of magnesium to take?

Magnesium oxide is at least as effective (if not better) at restoring and maintaining a healthy magnesium level in your cells and bones. Although magnesium oxide has a lower absorption rate, it contains much more elemental magnesium than other magnesium salts.

Should I take magnesium in the morning or at night?

Many people take magnesium at night because it can help them relax and sleep better. However, it does not cause drowsiness if taken during the day.

How do you know if you are magnesium deficient?

Some signs of magnesium deficiency include muscle spasms or cramps, loss of appetite, fatigue, weakness, abnormal heart rhythms, and pins and needles.

Will magnesium oxide help you sleep?

Any form of magnesium can help with sleep, but research shows magnesium glycinate may be most effective for enhancing quality sleep.


  1. Molecular weights: For the other magnesium salts, use the search box in the top right corner of the page.
  2. Ranade VV, Somberg JC. Bioavailability and pharmacokinetics of magnesium after administration of magnesium salts to humans. Am J Ther. 2001 Sep-Oct;8(5):345-57. PMID: 11550076
  3. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001 Dec;14(4):257-62. PMID: 11794633
  4. Altura BT, Wilimzig C, Trnovec T, et al. Comparative effects of a Mg-enriched diet and different orally administered magnesium oxide preparations on ionized Mg, Mg metabolism and electrolytes in serum of human volunteers. J Am Coll Nutr. 1994 Oct;13(5):447-54. PMID: 7836622
  5. Coudray C, Rambeau M, Feillet-Coudray C, et al. Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach. Magnes Res. 2005 Dec;18(4):215-23. PMID: 16548135
  6. Bertinato J, Plouffe LJ, Lavergne C, et al. Bioavailability of magnesium from inorganic and organic compounds is similar in rats fed a high phytic acid diet. Magnes Res. 2014 Oct-Dec;27(4):175-85. doi: 10.1684/mrh.2014.0374. PMID: 25635418
  7. Ranade VV, Somberg JC. Bioavailability and pharmacokinetics of magnesium after administration of magnesium salts to humans. Am J Ther. 2001 Sep-Oct;8(5):345-57. PMID: 11550076
  8. Musso CG. Magnesium metabolism in health and disease. Int Urol Nephrol. 2009;41(2):357-62. doi: 10.1007/s11255-009-9548-7. Epub 2009 Mar 10. PMID: 19274487

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  1. Gaetane White

    January 21, 2017 , 6:59 am

    I take magnesium glycinate that is easily absorbed because it is carried to your cells bound to the amino acids, along with Biomed BoneSure, a plant based calcium. I am not convinced from the above argument for magnesium oxide but I would be interested in hearing your comments comparing the two magnesiums. I feel the above argument is based on someone with adequate stomach acid and no problems with the laxative effect found with most magnesium. Thank you.

  2. Monica

    January 25, 2017 , 8:17 am

    Hi Gaetane,

    Yes, Biomed BoneSure actually uses AlgaeCal calcium, which is stated on their label. Lara is currently in the middle of a writing project, but I’ll be sure to reach out to her for a response to your glycinate comment when she becomes available again.

    – Monica @ AlgaeCal

  3. Lara Pizzorno

    January 31, 2017 , 3:56 pm

    Hi Gaetane,

    Monica let me know about your question and I’ve been busy working on some new articles so sorry I’m just getting to this now.
    First, thanks for your great questions. Unfortunately, the internet is loaded with “myth-information.” This is why I always read the full medical journal articles and don’t even trust the abstracts, much less the way findings are reported to the public, particularly by those with a vested financial interest in finding a “selling” point for a product.

    Regarding magnesium absorption

    Regardless of whatever type of magnesium salt is consumed (with ONE possible, but as yet unproven exception discussed below), during digestion, the magnesium will be disassociated from its stabilizing partner. This will happen regardless of whether the partner is an amino acid like glycine or an organic acid like citrate or an element like oxide. This separation of magnesium from its partner releases magnesium in its ionized form, which is the form in which magnesium is absorbed, and the primary form in which it circulates in the bloodstream.

    FYI – “chelated” is a buzz word used to sell certain types of magnesium supplements. It simply means “bound to a Krebs cycle intermediate,” i.e., that the magnesium salt partner is a Krebs cycle intermediate, such as citrate, glycinate, etc. Yes, these forms are more quickly bioavailable. No, that does not equal “optimal.” The Krebs cycle intermediates, like glycinate and citrate, are more easily detached from the elemental magnesium contained (more soluble), freeing this magnesium for absorption more rapidly, but they are detached before the magnesium is absorbed. The magnesium in magnesium glycinate is not absorbed intact and delivered to your cells.

    Glycine is a non-essential amino acid – the simplest of all the amino acids. It’s a non-essential amino acid because our bodies make it and use it to produce many types of proteins, including purines. Purines are used to make adenine and guanine, two of the five two of the five bases in nucleic acids that make up our DNA and RNA, and are also key components in other important biomolecules, including the energy currency of the body, ATP. The point here is that your body has many uses for the glycine chelated to magnesium in a magnesium glycinate supplement. This glycine will be disassociated during digestion, and although some may later combine with free magnesium in the bloodstream, most will be utilized for other purposes. In sum, glycine has no impact on our absorption of magnesium — other than that glycine is easily disassociated from magnesium, quickly freeing the magnesium for absorption, mainly in the lower parts of the small intestine, with small amounts absorbed in the colon.

    The same is true for all the other forms of magnesium salts – with one possible exception: magnesium threonate. Cell and animal studies indicate that magnesium threonate crosses the blood brain barrier, increases intracellular concentrations of magnesium in the central nervous system, and has a number of beneficial effects on neuronal plasticity.

    Slutsky I, Abumaria N, Wu LJ, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010 Jan 28;65(2):165-77. doi: 10.1016/j.neuron.2009.12.026. PMID: 20152124
    Sun Q, Weinger JG, Mao F, et al. Regulation of structural and functional synapse density by L-threonate through modulation of intraneuronal magnesium concentration. Neuropharmacology. 2016 Sep;108:426-39. doi: 10.1016/j.neuropharm.2016.05.006. Epub 2016 May 10. PMID: 27178134

    Whether the magnesium threonate complex is absorbed intact from the digestive tract into the bloodstream is not known. Most of the magnesium in the bloodstream (~55 to as much as 80%) remains in its free, ionized form (specifically, this form is a cation, which is an ion that is missing one or more electrons and therefore has a positive charge; cations are almost always minerals with a positive charge). About 33% of the free, ionized magnesium absorbed from the digestive tract binds to proteins in the bloodstream, and about 12% of it gets complexed with anions, which are typically chemicals that are negatively charged. Threonate is one such anion.

    Nutrient Metabolism, Structures, Functions and Genes, ed. Kohlmeier M, 2nd ed. , Academic Press, Elsevier, 2015, p. 745
    Magnesium in Laboratory Evaluations for Integrative and Functional Medicine, 2nd ed, Ed. Lord RS, Bralley JA. Metametrix Intitute, Duluth, GA, 2008, pp. 84-85.

    Threonate is a small sugar molecule naturally produced in our bodies. It’s formed as a result of our metabolism of vitamin C – specifically, by the spontaneous conversion of the product of ascorbic acid oxidation (which is called dehydroascorbic acid [DHA]), into oxalic acid and threonic acid (aka threonate).

    Threonate can definitely bind to free magnesium in the bloodstream, and the resulting complex can be carried into the brain by glucose transporters (GLUTs), which transport sugars (monosaccharides) and other small carbon compounds into the brain via passive facilitated transport.

    Or magnesium L-threonate might be absorbed intact directly from the digestive tract into the bloodstream and then carried into the brain by GLUTs. We don’t know.
    What we do know from the animal research is that supplementation with magnesium L-threonate resulted in increased intracellular Mg+ levels in the cerebrospinal spinal fluid. Because of magnesium’s critical importance for healthy brain function, these promising results are being investigated as a potential means of helping to maintain healthy brain function and to prevent cognitive decline and Alzheimer’s.
    What the animal research has not shown is that magnesium L-threonate was absorbed intact from the digestive tract and delivered to the brain. It’s entirely possible that the large amount of threonate consumed when magnesium L-threonate was given was first separated from the magnesium in the digestive tract, but later combined with it in the bloodstream, and the resulting magnesium L-threonate complex made its way to the brain.

    Furthermore, other research suggests that threonate, in the form of calcium L-threonate might be helpful for bone, but only if threonate exerts additional effects on osteoblasts and/or osteoclasts since calcium threonate is not as well absorbed as calcium carbonate. L-theanine’s fractional calcium absorption rate is 26.49 ± 9.39 %. Wang H, Hu P, Jiang J., 2013. Calcium bioavailability of calcium L-threonate in healthy Chinese subjects measured with stable isotopes ((4)(4)Ca and (4)(2)Ca).Eur. J. Clin. Pharmacol. 69, 1121e1126 Eur J Clin Pharmacol. 2013 May;69(5):1121-6. doi: 10.1007/s00228-012-1420-5. Epub 2012 Nov 16. PMID: 23229796 In comparison, the fractional absorption rate of calcium carbonate is 39 +/-0.7. Martin BR, Weaver CM, Heaney RP, et al. Calcium absorption from three salts and CaSO(4)-fortified bread in premenopausal women. J Agric Food Chem. 2002 Jun 19;50(13):3874-6. PMID: 12059174

    To date, all we have to support added benefit from calcium L-threonate is one in vitro (test tube) study of rabbit osteoclasts that were treated with sodium L-threonate, calcium L-threonate or calcium gluconate. Both sodium L-threonate and calcium L-threonate lowered the bone resorption activity of rabbit osteoclasts, but calcium L-theonate did a better job of it – and calcium gluconate was ineffective. He JH, Tong NW, Li HQ, et al. [Effects of L-threonate on bone resorption by osteoclasts in vitro]. [Article in Chinese] Sichuan Da Xue Xue Bao Yi Xue Ban. 2005 Mar;36(2):225-8. PMID: 15807273

    In sum

    All of the above does suggest that the organic anion, threonate, has beneficial effects on magnesium utilization in the brain. After much searching, I was finally able to find out how much elemental magnesium is present in a magnesium threonate supplement. It was not easy to discover, which makes sense because it is not much: 2,000 mg worth of magnesium threonate contains 140 mg of elemental magnesium, which translates to a 150 mg capsule delivering ~10.7 mg of magnesium.

    Back to magnesium glycinate

    Magnesium glycinate did not show superior bioavailability to the other Krebs cycle intermediates in the extensive review of the PubMed research I conducted when I wrote the Magnesium Oxide post.
    And even if magnesium glycinate had shown better bioavailability, remember, a fast, high rate of absorption is not necessarily optimal. What matters most is the amount of magnesium in the magnesium salt. If you take a supplement containing 150 mg of a magnesium salt that actually provides just 10 mg of elemental magnesium (e.g., Magnesium threonate, for example, see below), and you quickly absorb all the magnesium from it, you get less benefit than if you take a 150 mg supplement of a magnesium salt that contains 80 mg of elemental magnesium that you absorb slowly. Not only will you be getting far less elemental magnesium in the first salt, but you will excrete more of it if it’s bioavailability causes blood levels to quickly increase and reach a level higher than that our bodies rigorously maintain in the bloodstream. Magnesium glycinate is 14% elemental magnesium, which translates to 4.8 mg of magnesium per 150 mg capsule – even less magnesium than is provided by magnesium L-threonate.

    Regarding magnesium’s “laxative effect”

    The carrier for magnesium into our cells is the activated form of B6, which is called pyridoxal-5-phosphate (P5P). A fairly large percentage of the population has inherited SNPs (single nucleotide polymorphisms) that render the enzymes that convert B6 to P5P very slow / much less active – including yours truly, which is why I take P5P along with AlgaeCal Plus. I discovered this in a roundabout way when I began taking sufficient vitamin D3 for my needs, which increased my ability to absorb calcium – and also increased my needs for magnesium. A possible topic for another post.
    Here the key point is that if taking magnesium is resulting in diarrhea, this may indicate P5P is needed or more magnesium is being consumed than the body can absorb. 25 mg of P5P taken along with any supplement that provides magnesium should be very helpful – and P5P is quite safe and inexpensive. Also, many supplements contain magnesium – anyone who is experiencing loose stools should check ALL the supplements being taken and add up how much supplemental magnesium overall is being consumed. It could just be that much more magnesium is being taken than realized.

    I remember about 10 years ago, a patient of my husband’s (Dr. Joe Pizzorno) came to us with severe migraines. He was a high-level business man under a great deal of chronic stress, so magnesium was suggested. (Stress causes increased loss of magnesium.) His migraines went away, but after a couple of years, he developed explosive diarrhea. First, we had him add up all the magnesium he was taking from all the supplements he used, plus his meal replacement drink mixes – and it turned out to be a staggering amount! He cut back on the amount of magnesium he was consuming, and the diarrhea immediately stopped — but even though he was still getting plenty of magnesium, his migraines came back. Research showing a high incidence of SNPs that result in slow conversion of B6 to P5P was just coming out, and if you cannot convert B6 to P5P effectively, you cannot get magnesium into your cells, so I suggested P5P. Within days, he had no more migraines and no more diarrhea, and he has been fine since.

    I suggest you consider a trial of 25 mg of P5P taken when you take any magnesium supplement. Below are the citations for a couple of the most recent papers underscoring the importance of B6 for our ability to utilize magnesium. But, given the number of individuals who cannot effectively convert B6 into P5P, the form in which it gets magnesium into our cells, P5P is the best choice (I also wrote about this in Your Bones, 2nd ed., pp. 231-2).

    Spasov AA, Lezgitsa IN, Kharitonova MV, et al. [Effect of some organic and inorganic magnesium salts on lipoprotein state in rats fed with magnesium-deficient diet]. [Article in Russian] Eksp Klin Farmakol. 2008 Jul-Aug;71(4):35-40. PMID: 18819439
    Spasov AA, Petrov VI, Iezhitsa IN, et al. [Comparative study of magnesium salts bioavailability in rats fed a magnesium-deficient diet]. [Article in Russian] Vestn Ross Akad Med Nauk. 2010;(2):29-37.PMID: 20364677

    Thanks again, Gaetane. I hope this information will be helpful to you.

  4. Shameer Mulji

    October 5, 2019 , 4:53 pm

    “I suggest you consider a trial of 25 mg of P5P taken when you take any magnesium supplement.”

    Should P5P be taken during the same meal as magnesium or will taking it during separate meals yield the same result?

  5. Blaire AlgaeCal

    October 8, 2019 , 9:10 am

    Hi Shameer,

    Good question! It is best to take P5P at the same time as when you take magnesium.

    Let us know if you have any further questions ?

    – Blaire @ AlgaeCal

  6. Orkun

    October 28, 2022 , 2:04 am

    Hi Lara,

    Thanks for this independent article.

    Simplicity is sometimes the key to solve very complex problems, let me add simple facts to you:

    – Mg in blood has upper limits so the key to mg supplement is to give it to the blood slowly in time. Best form is mg oxide and best way to absorb it is to take 10 or 20 divided doses of mgO throught the day. 20mg each 30 mins or 40mg each hour.

    – Do not forget that Mg in sunflower seeds or in nuts are exist in nature in very divided doses on each small sunflower seed 🙂 So you have to eat it very slowly and with patience.

    Best regards.

  7. Shelby AlgaeCal

    October 28, 2022 , 10:31 am

    Hi Orkun,

    Thank you for reaching out! We completely agree that simplicity is sometimes key, and we appreciate you sharing this with us!

    If you have any further feedback, questions, or concerns at any time, please let us know – additionally, you’re always welcome to call us at 1-800-820-0184!

    – Shelby @ AlgaeCal

  8. Ella Bird

    February 28, 2024 , 10:57 am

    This information is awesome!! Thank you so much for your time and expertise and writing this in an understandable way. My son had a reaction to Ciproflaxin and had horrible pins and needles (neuropathy) and muscle weakness… He is now having eye issues with floaters and “snow”. I have been giving him magnesium oxide but a functional Dr told him to take the magnesium glycinate which gave him headaches and nightmares. He only weighs 130lbs on the smaller side for a younger man. Do you have any suggestions. He has not been tested for MTHFR. He was taking Nerve Complex but we had to cut down the dose to 1/4 as his pins and needles got worse. We are now taking Magnesium Complete which is and Oxide which has a sucrosomial delivery and this has taken away the pins and needle feeling. He has been tested for all neurological possibilities and been blessed with no underlying condition. Online population of people being “floxed” by fouride based antibiotics is scary to read. His neurologist said his eye issues are central nervous system based so I am wondering if the magnesium threonate would help. Any suggestions or ideas would be appreciated. Thank you for your wonderful work!!! I so appreciated the article!

  9. Yoori AlgaeCal

    February 28, 2024 , 2:22 pm

    Thank you so much for reaching out, Ella! I’m truly sorry to hear about your son’s struggles with his health, but I’m glad to hear that the information provided was helpful to you :). We will be emailing you to provide personalized support for you, so please keep an eye out!

    – Yoori

  10. Joyce

    February 22, 2018 , 7:28 am

    I use Gly mag as I have read it is the best absorbance. So I am annoyed at this whole different list of magnesium traits and uses. It’s like the cereal isle in the supermarket.

  11. Jenna AlgaeCal

    February 27, 2018 , 1:14 pm

    Hi Joyce,

    Thank you for taking the time to comment, we truly appreciate your feedback. You’re right, shopping for magnesium can feel like browsing the cereal aisle in the supermarket! This is why Lara reviewed the latest research to help our readers better understand the different forms of magnesium & make informed decisions when purchasing! In regards to magnesium glycinate specifically, Lara discusses it in-depth in her response just above this comment. We hope this is helpful, Joyce!

    – Jenna @ AlgaeCal

  12. Georgiana Yasko

    January 21, 2017 , 8:25 am

    Thank you for the education!

  13. Judy

    January 21, 2017 , 8:58 am

    I thought this was a very interesting and enlightening article. Would this apply to magnesium glycinate as well and magnesium threonate? My understanding is that mag. threonate crosses the blood brain barrier.

  14. Monica

    January 25, 2017 , 8:12 am

    Hi Judy,

    Lara discusses glycinate and its elemental magnesium and absorption briefly in the first table of the post. She’s currently working on a writing project and is unavailable at the moment, but I’ll be sure to reach out and try and get a response to your question when she becomes available again.

    – Monica @ AlgaeCal

  15. Monica

    January 31, 2017 , 4:01 pm

    Hi Judy,

    Lara has written an in-depth response on magnesium glycinate and threonate in reply to Gaetane’s question above. It should also answer yours as well.

    – Monica @ AlgaeCal

  16. Connie

    January 21, 2017 , 5:26 pm

    I haven been taken algaeCal and Strontium Boost for 3 months and I realize that one of this pill is making my vowel movement very soft. Perhaps too much magnesium? Or something else? Please. Advise me what to do.
    Since then my vowel movements are not normal, they are only when I stop taken for few days.

  17. Monica

    January 23, 2017 , 8:17 am

    Hi Connie,

    Thanks for sharing. Magnesium is a natural laxative, so if you are taking an additional magnesium supplement, this may be why your bowel (I’m guessing that’s what you meant by vowel) movements have been soft. AlgaeCal Plus is formulated with the optimal 2:1 calcium to magnesium ratio for both absorption and bone health – so if you are getting more magnesium than calcium through your diet this may also be the reason. If you’d like to call in and speak with one of our Bone Health Advisors we can dig in more as to why this may be happening (there could be other factors as well). You can call us Canada and USA toll free at 1-800-820-0184 from Monday through Friday: 6am to 4pm (PST)
    and Saturday & Sunday: 8am to 2pm (PST).

    – Monica @ AlgaeCal

  18. Jeff

    May 15, 2019 , 11:42 am

    With Mag. Oxide, my vowel’s are consonant! .

  19. Wendy Nevatt-Dakan

    January 22, 2017 , 11:17 am

    I am taking plant based magnesium aquamin seawater 500mg, since I am on the basic algaecal and am supplementing. Where does that fit?

  20. Monica

    January 23, 2017 , 8:12 am

    Hi Wendy,

    The optimal ratio of calcium to magnesium is 2:1. If you are taking 3 capsules per day of AlgaeCal Basic that gives you 750 mg of magnesium and 65 mg of magnesium. If you are taking additional magnesium, then it would be recommended to try and get as close to the 2:1 ratio as possible, unless your doctor or naturopath has recommended otherwise.

    – Monica @ AlgaeCal

  21. Deborah

    March 1, 2018 , 9:52 pm

    I just ordered AlgaeCal Plus and Strontium Boost. I have been taking the Jigsaw bran of sustained release magnesium supplements which is in the form of Dimagnesium Malate. Where does that fit in with the various forms of magnesium?

    Thank you!

  22. Lara Pizzorno

    March 8, 2018 , 11:25 am

    Hi Deborah,

    Despite the wonderful sounding claims made by Jigsaw, no published research confirms any of them. I did a thorough search (Pub Med, Google Scholar, Science Direct) and could not find a single paper providing evidence of any of these claims – the only paper I saw in which Mg malate was evaluated was conducted in 1995 and suggested that Mg malate may be helpful for fibromyalgia. No follow up studies were conducted. (Here’s the citation for that: Russell IJ, Michalek JE, Flechas JD, Abraham GE. Treatment of fibromyalgia syndrome with Super Malic: a randomized, double blind, placebo controlled, crossover pilot study. J Rheumatol. 1995 May;22(5):953-8. PMID: 8587088). The “source” given in support of Jigsaw’s claims is another promotional article, not an article published in a medical journal.

    So, I don’t know how magnesium malate compares to other forms of magnesium. What I could find was information on the amount of elemental magnesium in Mg malate compared to other forms – copying this in here – supposedly this info was taken from NIH website, but I’m not sure it’s accurate for the other forms, know it is not accurate for Mg oxide. Note that this source continues to cite the urban myth that Mg oxide has only 4% bioavailability – see my article for full explanation of why this is incorrect – bioavailability is actually 23% for Mg oxide.

    Anyway, here’s what I was able to find re Mg malate compared to other Mg salts:

    Magnesium Sulfate —> Elemental Mag = 10%, Bioavailability = ?
    Magnesium Chloride —> Elemental Mag = 12%, Bioavailability = ?
    Magnesium Oxide —> Elemental Mag = 60%, Bioavailability = 4%
    Magnesium Carbonate —> Elemental Mag = 45%, Bioavailability = 30%
    Magnesium Hydroxide —> Elemental Mag = 42%, Bioavailability = ?
    Magnesium Citrate —> Elemental Mag = 16%, Bioavailability = 90%
    Magnesium Lactate —> Elemental Mag = 12%, Bioavailability = 99%
    Magnesium Glycinate —> Elemental Mag = 18%, Bioavailability = 80%
    Magnesium Malate —> Elemental Mag = 6.5%, Bioavailability = ?
    Magnesium Taurate —> Elemental Mag = 9%, Bioavailability = ?

    Also note, on Jigsaw’s promotional page, they make a big deal of their SRT (slow release technology) saying that slow release avoids digestive issues (they’re referring to osmotic diarrhea here). Mag oxide NATURALLY is released slowly. If taking this product feels effective for you, then great! If you want to confirm efficacy, I suggest having an RBC magnesium lab test run – I discuss this lab in the Labs Appendix in Your Bones, 2nd ed.

  23. MoneyMan

    March 13, 2018 , 2:26 am

    Now that’s proper research.
    Finally someone explaining it appropriately instead of just parroting what others say.

    Thank you

  24. Isaiah

    March 22, 2018 , 1:42 pm

    I like this article. But what are your thoughts on strontium? You guys have a Strontium supplement that contains 680 mg.


  25. Jenna AlgaeCal

    March 27, 2018 , 10:43 am

    Hi Isaiah,

    Lara has written extensively on the research behind strontium – including the different forms and optimal bone-building dosage of 680 mg. You can read it by clicking here!

    – Jenna @ AlgaeCal

  26. Ken

    May 17, 2018 , 7:04 am

    Lara, great information! I have been looking into optimizing my magnesium intake. I am looking at various products, and am also considering creating my own magnesium bicarbonate using magnesium hydroxide powder and carbonated water. Where does this form/method fit into the scale of effectiveness?

  27. Jenna AlgaeCal

    June 1, 2018 , 12:53 pm

    Hi Ken,

    After reaching out to Lara with your question, she suggests checking out her reply to Deborah which includes magnesium hydroxide in a list of comparisons.

    Lara also suggests taking 25 mg P5P along with your magnesium drink. For more information on P5P, please see her response to Gaetane’s comment 🙂

    – Jenna @ AlgaeCal

  28. Ed

    May 29, 2018 , 11:25 am


    “Magnesium oxide was virtually insoluble in water and only 43% soluble in simulated peak acid secretion (24.2 mEq hydrochloric acid/300 ml). Magnesium citrate had high solubility even in water (55%) and was substantially more soluble than magnesium oxide in all states of acid secretion. Reprecipitation of magnesium citrate and magnesium oxide did not occur when the filtrates from the solubility studies were titrated to pH 6 and 7 to stimulate pancreatic bicarbonate secretion. Approximately 65% of magnesium citrate was complexed as soluble magnesium citrate, whereas magnesium complexation was not present in the magnesium oxide system.”

  29. Jenna AlgaeCal

    June 1, 2018 , 1:01 pm

    Hi Ed,

    Thanks for commenting! For a full review of the different forms of magnesium supported with numerous references please read Lara’s post above (there’s lots of valuable information in the comments below too).

    – Jenna @ AlgaeCal

  30. Mary

    September 16, 2018 , 7:31 pm

    I just purchased a Droughtmaster Traveler 10 that makes drinking water from humidity. The water is from my greenhouse. Water is glacial and sweet and is doing amazing things physically, but has no Magnesium. Was researching Prill…magnesium oxide to treat the water and found your statement. Thank You! The pH is 6.5 from the device but will it alkalize further with magnesium oxide?

  31. Jenna AlgaeCal

    September 24, 2018 , 3:21 pm

    Very interesting, Mary! Our expertise is specific to bone health, and we’re sorry we aren’t very familiar with the effects of magnesium oxide being used with a water generator.

    Hopefully the company you purchased from would have some insight and we highly recommend contacting them for their best suggestions! 🙂

    – Jenna @ AlgaeCal

  32. Andrew Letourneau

    November 22, 2018 , 6:50 pm

    I have been informed by a friend that magnesium salts/oils are all the rage. How do they get absorbed into the bloodstream? That is, how is the elemantal magnesium separated from the binder to be of use? Does the first table still apply?

  33. Jenna AlgaeCal

    November 27, 2018 , 10:56 am

    Hi Andrew,

    Lara Pizzorno explains how magnesium is absorbed near the bottom of the article (second last section)!

    “The lower parts of the small intestine are the primary sites of magnesium absorption. However, magnesium is also absorbed throughout the entire intestinal tract. Magnesium does not have special carriers that pull it into the bloodstream. Its absorption is a passive transcellular process.

    For this kind of absorption process, the quantity of magnesium that passes through the digestive tract is the major factor controlling the amount of magnesium that is absorbed.”

    – Jenna @ AlgaeCal

  34. Michal W

    December 17, 2018 , 7:16 am

    Hi Lara,

    Your info about Mg oxide was shock to me. It seems I’ve been victim of this myth too. Anyway, you encouraged me to try this form myself.

    But I have question regarding B6 and P5P
    By accident I found P5P (25 mg sublingual) to be effective for my withdrawal symptom from antidepressant cocktail: tension that ends with fury (I have to kick and shout; never had this in my life before).

    My B6 is actually HIGH (2x times the norm; I checked it about the same time but was expecting the opposite).
    This didn’t seem to make sense to me as a layman until I found some statement that it’s because B6 is not absorbed and is just circulating in the blood?
    There’s only one place I found it, so I treated it with caution.

    Can you shed some light or give some references where I could read?
    I know P5P works! The problem is that not always – sometimes like a charm and sometimes just a bit or nothing (been using it for a few months).

    Since about a week I am experimenting with Mg lactate (120 mg of free Mg, 3x/day) and also found it helps sometimes for my tension.

    I am taking Mg (lactate)
    – morning and evening as routine 120 mg
    – when tension hits (i.e. every day) 120 – 180 mg
    Does it seem good routine? Or would it be better to take only during tension but higher amounts?

    It’s all (Mg – P5P, B6 – P5P connections) very important as now I have not only depression with severe strange somatizations but also withdrawal symptoms.

  35. Lara Pizzorno

    December 20, 2018 , 3:31 pm

    Hi Michal,

    Since P5P helps and B6 levels are elevated, I believe your genetic inheritance includes SNPs in the enzyme responsible for converting B6 to P5P that render this enzyme ineffective, and render you unable to effectively make this conversion. By taking B6, you will not be providing the P5P required for methylation. Dysfunctional methylation – specifically a dysfunctional COMT enzyme — can compromise clearance of stress hormones, producing tension, anxiety and depression. Methylation requires the activated forms of not just B6, but also folate, B12 and riboflavin. I suggest you try taking B Active (the BioClinic Naturals product we use that provides all the Bs in activated forms), which may help a lot. Also, you should have your 23&me genomic profile run, so you can access your raw data and have it analyzed to confirm which SNPs you have in, not only B6 but all the B vitamins, that might compromise their activation and thus your methylation capacity.

    Re magnesium, low intake of magnesium definitely promotes depression and anxiety;

    But I was unable to find any papers specifically stating that magnesium lactate is more effective than other forms. If you are not experiencing loose bowels from taking the amounts of magnesium lactate you mention, then it should be fine for you. If you are hypochlorhydric (produce little stomach acid), you may find magnesium citrate is even more helpful since this magnesium salt will disassociate without stomach acid. One caveat here – your intake of magnesium should be in balance with that of calcium. The ratio between them should be 2:1, calcium: magnesium.

    Hope this helps, please keep me posted and don’t hesitate to write back with further questions,

    Be well, Lara

  36. Geoff

    January 23, 2019 , 9:16 am

    Unless I am much mistaken, the expansive comment on forms of magnesium Lara wrote on Jan 31, 2017 contains a glaring error. When describing the amount of magnesium in magnesium glycinate she says that it is 14% — a number I confirmed elsewhere. She then goes on to say this translates to 4.8mg in a 150mg capsule. By my math 14% of 150mg is 21mg or over four times as much as the 4.8mg stated — and twice as much as magnesium threonate which she compares it to. Am I missing something?

  37. Lara Pizzorno

    January 30, 2019 , 9:56 am

    Hi Geoff,

    Yes, you are not factoring in the impact of the 3rd column in the table — % of Elemental Mg Absorbed. Magnesium glycinate is 14% elemental magnesium, but only ~23% of that 14% is actually absorbed. So, 150 mg x 14% does = 21, but then you have to take 23% of 21, which = 4.8 mg, and this is the amount of elemental magnesium actually absorbed when a 150 mg capsule is consumed. Thanks for asking for clarification!

    Be well, Lara

  38. Tom White

    March 2, 2019 , 7:51 am

    Dear Lara,

    Thank you for writing this helpful and valuable article.

    I am currently consuming a very low carbohydrate diet due to my personal health conditions (which include candida overgrowth, Blastocystis Hominis parasite infection, Bacterial dysbiosis, mould allergy and many food allergies and intolerances). I am working with my practitioners to help improve these conditions.

    However, this limited diet means that my fibre intake is low and my diet is currently an organic foods diet which is a high fat, moderate protein and low carb diet consisting of hemp seed powder, barley grass powder, coconut cream, and grass fed butter or ghee.

    Therefore I take Magnesium supplements to improve bowel regularity and eliminate mild constipation on this relatively “low fibre” diet.

    I cannot eat or chew any food because I have TMJ disorder (jaw joint osteoarthritis) and therefore eating or chewing is very painful. I blend all of my food or used pre-ground organic foods from the health food shop (e.g. hemp powder rather than hemp seeds).

    I currently take 12ml of Nutricology Magnesium Chloride per day spread out evenly throughout the day in my drinking water, which helps with regularity and also reduces my TMJ pain.

    I also take 2 tablets of NOW Magnesium Citrate 200mg per day (one with breakfast, one with dinner). This product also helps with the bowel regularity and reducing my TMJ symptoms.

    I want to continue with the Nutricology magnesium chloride but perhaps try a different product rather than the NOW magnesium citrate to see if I can experience even further benefits.

    If you were me, which product on the market would you take as a stand alone magnesium supplement? If you would take magnesium oxide, which specific product would you take? I am not asking you to officially recommend a product but if you can suggest a product, that would be very helpful for me because my current bottle of NOW magnesium citrate will run out in 3 days.

    Also, I cannot currently take AlgaeCal because I need to individually manage and adjust my dosages of Calcium, Vitamin D3, K2 and Zinc to help with my other health conditions.

    I look forward to your reply and thank you in advance

    Warmest regards,

    Tom White.

  39. Tom White

    March 2, 2019 , 8:22 am

    Also, I wanted to ask about how much daily magnesium supplementation I need to take to reach the RDA for my age group.

    I am 29 years old.

    The RDA for Magnesium for a 29 year old male is 400mg, as stated at the weblink below:

    If I am taking a magnesium supplement which provides 400mg of Magnesium Citrate per day, does that mean I have met my RDA for that day?

    Or do I need to take 400mg of actual elemental magnesium and then factor in the amount that is absorbed, as stated in your article?

    According to your article, 400mg of Magnesium Citrate per day would only give me 13.2mg of magnesium that is actually absorbed (using the figures in the comparison table).

    Does that mean I need to take 30 times more magnesium citrate in order to get 400mg of magnesium that is actually absorbed?

    I look forward to your reply and thank you in advance

    Warmest regards,

    Tom White.

  40. Lara Pizzorno

    March 27, 2019 , 3:21 pm

    Hi Tom,

    Sorry it has taken me some time to get back to you – please accept my apologies. I’ve just been maxed!

    Since you are dealing with numerous intestinal pathogens, many of which love citrate and use it as a favorite food source, I suggest you switch from magnesium citrate to another magnesium salt.

    The one that may work best for you is magnesium hydroxide. This is the magnesium salt used as a laxative in Milk of Magnesia. It’s used as a laxative because hydroxide ions are very effective at attracting and retaining water in the intestines, which increases peristalsis and evacuation of the bowel. So, although magnesium hydroxide increases potential for diarrhea in most folks, in your case, it may be the most beneficial form.

    Magnesium hydroxide is 42% elemental magnesium and has a bioavailability of 15%. You can compare this to the other forms of magnesium in the table in this article. I did not include magnesium hydroxide in this article because of its laxative effects, but again, in your case, it may be just what you need. The label on the supplement you purchase should specify how much elemental magnesium is present in the dose of magnesium hydroxide it provides.…/magnesium_hydroxide…

    Given the complexity of the issues you are dealing with, if you have not already had the OAT run (Organic Acids Test offered by Great Plains Lab), I suggest you discuss having this done with your doctor(s). A few weeks ago, I taped an #AskLara on the OAT, which you can access on The AlgaeCal Community – just enter #AskLara OAT in the search box on the left hand side of the page.

    Lastly, if you could possibly include the amounts of calcium, D3, K2 and zinc that are present in AlgaeCal Plus as part of the dosages of each that you need to take, I hope you will consider starting AlgaeCal Plus as soon as possible because it will also be giving you several forms of plant-derived calcium, plus magnesium oxide (which you can read more about it my post on AlgaeCal), plus boron, plus a wide array of trace minerals (including excellent amounts of silicon and some zinc (30.1 mcg/g of zinc. The full dose of AlgaeCal Plus contains 2.4 grams, which means it contains 72.24 mcg of zinc – not tons, as I expect you are taking at least 30 mg/d but still potentially helpful.

    Do keep me posted on how you are doing,

    BE WELL,


  41. David Abner

    March 18, 2019 , 7:36 pm

    By this same reasoning, shouldn’t magnesium sulfate also be a cost effective it’s supplement? 1 gram of epsom salt contains 100mg elemental magnesium, and it’s well below the laxative threshold. Plus an 8lbs pound bag (3,630 grams) can be found at Walmart for $5. Thoughts?

  42. Michael

    May 24, 2019 , 6:59 pm

    What are your thoughts on the relatively new sucrosomal (liposomal) magnesium? I found a study which shows very good absorption even compared to mag oxide.

  43. Lara Pizzorno

    May 30, 2019 , 9:07 am

    Hi Michael,

    Thanks for sharing this interesting study with me! This product may be helpful for you.

    Here’s my review of the study:

    As you may have noted, sucrosomial magnesium is magnesium oxide to which sucrose esters have been added in an attempt to increase absorption/bioavailability.

    You may also have noted that this it was a very small study – just 10 participants whose average age was 34. And they excluded from the study anyone with “history of bone diseases, diabetes mellitus, chronic fatigue syndrome, premenstrual symptoms, peptic ulcer, intestinal resection, inflammatory disease of the gastrointestinal tract, malabsorption/maldigestion, hypertension, gall bladder disease or any other relevant medical condition; current chronic medication intake; history or current abuse of drugs, medication or alcohol, or intake >2 alcoholic beverages/day; known hypersensitivity to study product or any ingredient in the preparation” – so, in sum, we have 10 young healthy study participants with good digestion and ability to absorb minerals.

    Look at Table 1 – you’ll see that magnesium oxide concentrations compare very favorably with those of sucrosomial magnesium in the blood and in red blood cells (RBC is, as you know a far better indicator of magnesium uptake and actual use than blood/serum). The place where the difference in concentration is noticeable is urine – which is a marker of magnesium’s elimination from the body, not its absorption into and use in our cells. RBC is the best indicator for our effective use of magnesium.

    The box plot diagrams make it look like sucrosomial magnesium is more effective because they are comparing initial concentration to 24 hours later, and magnesium oxide concentrations were higher initially than those of sucrosomial magnesium, so I found that a bit misleading for readers who are not used to evaluating research papers.

    Also, it seems strange to me that they stress how much more sucrosomial magnesium was found in urine since what this most likely shows is that absorption occurred so rapidly that the body’s pathways for moving the bolus of magnesium that was absorbed from the intestines into our cells became saturated, so far more sucrosomial magnesium was excreted.

    Despite all this – the sucrosomial magnesium product appears to be safe and might be helpful for you. If you can access this product, why not give it a try and see how you feel?

    Hoping you find it helpful,


  44. Sam

    May 28, 2019 , 7:17 pm

    This makes sense if one is DIY’ing their magnesium.

    Most of-the-shelf supplements deliver a specific amount magnesium, explicitly stated on the packaging e.g, 400mg elemental magnesium in 2 tablets.

    It’s worth noting this distinction, as assuming otherwise might have people taking 6X more than they need (in the case of Glycinate). Using the above example of 400mg per 2 tablets, this equates to 12 table which is a whopping 2.4grams of magnesium. Enough to make people quite sick.

  45. Yuri Davidovsky

    June 3, 2019 , 7:49 am

    An excellent article, far the best I have ever read on magnesium, lays out thing very clearly, logically and in an easy to understand fashion, something that many scientific papers are sorely lacking, unfortunately.

    However, there appears to be an error in the ‘Comparison of Magnesium Salts’ table, the elemental content of magnesium citrate should be 16%, rather than 11%, I can verify it by looking at supplement packaging on my desk, 1830mg of citrate contains 295.7mg of the element. The table at the bottom of this article also confirms it:

    Also the “Elemental MG Absorbed per 100 mg of MG Salt” value should be corrected upward from 3.3mg. From the 295.7mg at 30% absorption rate 88.75mg of Mg would be taken up, this would make it 88.75 / 18.3 = 4.85mg. Values for oxide appear to be correct in the table.

  46. Anon

    February 27, 2020 , 6:45 am

    No, that is not an error. Magnesium citrate (1:1) has 11% magnesium. Your supplement is the cheaper (and less soluble) trimagnesium dicitrate (3:2), which has 16% magnesium.

  47. Joel Bórquez

    July 5, 2019 , 1:31 pm

    Great article, i dind´t know of this page, but sure i will visit it from now.

  48. Megan AlgaeCal

    July 9, 2019 , 11:32 am

    Thank you for your kind words, Joel!

    We’re so glad you liked the article and hope you continue to enjoy the recipes, nutrition information, and exercises on our blog ?

    If you have any questions, don’t hesitate to give our Bone Health Consultants a call at 1-800-820-0184!

    -Megan @ AlgaeCal

  49. Yoda

    July 10, 2019 , 5:00 am

    Im confused as to the dosages implied from this article.

    Dietary magnesium absorption ranges from around 40-50% I believe,

    400mg is the approximate RDA for men, which yields a max of 200mg absorbed magnesium, assuming you reach the 400mg all from diet.

    My 4.2g scoop of magnesium citrate powder provies around 600mg elemental magnesium, and the label states this as 150% of the RDA.

    This 150% figure would only be correct if we assumed that the absorption of magnesium from its citrate salt falls in the same 40-50% range that is found in dietary magnesium. But, your chart clearly shows its 30%. So that 150% figure is inflated.

    My question is, is the RDA on supplements simply the amount of magnesium present, and fails to take into account the absorption rate of that specific salt compared to the standard absorption rate of diet?

  50. Lara Pizzorno

    July 16, 2019 , 11:30 am

    Hi Yoda,

    Great questions! Thanks.

    First, yes, the recommended dose that is listed on a supplement bottle is only how much elemental magnesium is present (I believe you meant the recommended dose on the product label, not the RDA?) and does not reflect the absorption rate or bioavailability of the type of magnesium salt provided.

    Regarding RDA, the RDAs for magnesium (420 mg /d for men and 320 mg/d for women ) do not properly balance the RDA for calcium, which is 1,000 mg per day for men up to age 70, then 1,200 mg per day for men as well as for women (and a number of recent papers have recommended up to 1,500 mg per day in postmenopausal women with bone loss issues).

    The optimal balance between calcium and magnesium is 2:1. So, we require 600 – 750 mg of magnesium daily – and possibly more if we are chronically stressed or exercise regularly at sufficient intensity to sweat vigorously (or live somewhere hot, like Arizona or Florida) because chronic stress or sweating will increase the rate at which we eliminate magnesium. Sweating, however, is really good for us – clears toxins!

    You mention your 4.2g scoop of magnesium citrate powder provides ~ 600mg of elemental magnesium, which sounds excellent. The only problem here is the issue I tried to explain in this post, which is that when a bolus dose of magnesium is provided, most of it will be rapidly cleared from the bloodstream by the kidneys and eliminated in urine. This would certainly be the case with 600 mg of elemental magnesium from magnesium citrate since citrate rapidly disassociates from magnesium in the stomach even without the presence of stomach acid.

    The goal is not just immediate bioavailability (how rapidly magnesium – or any water-soluble nutrient – is released and absorbed into the bloodstream), but magnesium’s release in smaller amounts over a longer period of time, thus maximizing our ability to use it effectively. If you do need additional magnesium, you might consider taking 1/3 of a scoop of your magnesium citrate powder at a time and spacing your doses out over the course of your day.

    However, you should know that consumption of too much magnesium can be harmful. The research shows that high intake of total calcium or magnesium only reduces risk of colorectal cancer when the Ca/Mg ratio is in the 2:1 range – a little higher is OK, but a lot higher is not OK. In other research — using data from the Women’s Health Initiative studies — excess magnesium in relation to calcium appeared to be detrimental to bone and increased fracture risk of the forearm and wrist. In China, where people tend to consume more magnesium and less calcium (they eat more vegetables, no dairy), consuming excessive amounts of magnesium actually increased risks of all-cause mortality and mortality due to CVD and colorectal cancer among women.

    The take-away here is that “more,” particularly in the case of supplements, is not always better! Remember, if you are taking AlgaeCal Plus, the full 4 capsule dose is giving you 720 mg of calcium properly balanced by 360 mg of magnesium in the form of magnesium oxide. Also, you’re taking a divided dose (2 capsules AM and 2 PM), so you are maximizing your ability to effectively use both the calcium and magnesium provided. To reach 1,200 mg of calcium / 600 mg of magnesium daily, your diet should be providing you with the remaining 480 mg of calcium and 240 mg of magnesium – unless you feel you have symptoms suggestive of magnesium insufficiency. In that case, you may want to ask your doctor about running an RBC (red blood cell) magnesium to check your status and supplementing with additional magnesium (or eating more magnesium-rich foods) if indicated.

    Regarding your comment about the amounts of magnesium in the chart — they are taken from research carefully evaluating and comparing the absorption rates among different magnesium salts, so I believe these amounts are more accurate than a generalization made in relation to dietary magnesium.

    Re dietary magnesium, a couple of additional factors to consider: The magnesium present in our foods is embedded in the matrix of whichever magnesium-rich food is being consumed. How much of it will be available, much less absorbed, depends on other factors present in the food (for example, its content of phytates and fiber), plus the digestive function of the person consuming the food. Here, a key question is whether this person is producing sufficient stomach acid. As you probably know, our ability to secrete stomach acid typically drops off as we age, plus many individuals now take acid blockers [e.g., PPIs, H2 blockers, OTC antacids), and/or suffer from infection with Helicobacter pylori, which interferes with stomach acid production, and its presence is extremely common. If all these potential issues weren’t troublesome enough, many of us have food allergies/sensitivities or dysbiosis that harms the lining of the digestive tract, promoting “leaky gut,” and that impairs nutrient absorption.

    Hope this helps. Be well!


  51. Lisa

    July 24, 2019 , 7:53 pm

    Thanks for this. A couple of years ago, my doctor recommended magnesium to help with my restless legs. I had been buying magnesium oxide, without paying any attention to forms of magnesium.

    After reading several articles saying magnesium oxide was the least bioavailable form, I bought magnesium gluconate. My restless legs returned. So, I tried chelated magnesium. Honestly, my legs were causing such insomnia that I was barely functioning.

    A few days ago, I happened upon your article. It confirmed what I had begun to suspect. So, I rushed out and bought a bottle of magnesium oxide. I’ve slept like a baby the last 3 nights.

    I’ve learned an important lesson about believing everything I read on the internet. I should have trusted my own experience. But I’m also glad to have found your confirmation. Thanks so much for your research, and for making it public.

  52. Megan AlgaeCal

    July 26, 2019 , 10:31 am

    Hi Lisa!

    Thank you so much for taking the time to share your story! We’re so happy to hear that you are now sleeping like a baby ? It gives us great joy to hear that our articles are helping others – feel free to browse through some of our other articles here if you’d like!

    -Megan @ AlgaeCal

  53. Lehua anakoni

    October 5, 2020 , 11:28 am

    I have jaw clenching and heart pounding from medication prescribed for ADHD. Tried magnesium l theronate, still had the muscle tightness and hypertension and jaw clenching. Magnesium chloride is good, better than oxide, but oxide is the second best in my experience, much higher bioavailability than the overpriced L theronate and citrate.

    I’d say magnesium chloride then magnesium oxide in bioavailability. The bioavailability is much higher than 4% for sure.

    I had an old bottle that I never took till I ran out of theronate, and surprised, delt much calmer and no more teeth grinding anxiety.

    I relived on DXM for the glutamate antagonist effects and magnesium lowers the DXM doses needed to relax.

    Don’t believe everything you read. Magnesium oxide does work at a much better price. The more expensive supplements aren’t always better.

  54. David

    August 5, 2019 , 2:08 am

    This is all extremely useful information with regard to magnesium intake.

    One thing I find perplexing is the RDA which is quoted as being 420mg for someone like me, and I’m wondering how I can ever take enough to attain this RDA level.

    With the low amount of Mg being absorbed by all the forms, it seems unlikely that I will ever achieve my 420mg daily target.

    If you have any comments on this, I would be very interested to read them.

  55. David

    August 12, 2019 , 5:12 am

    Thanks for the reply, it was very helpful.

    It seems that I’ve been under a misapprension with regard to magnesium intake. For RDA, I read that to mean that I need to absorb 420mg daily. It appears that this is incorrect and it actually means I need to ingest 420mg daily.

    That being the case, there will no doubt be much variation in absorption of magnesium depending on which form a person takes. It also makes the using of RDAs virtually redundant due to large variations in absorption rates of the type of magnesium that was used.

    I would appear that this subject is far more complicated than I first thought.

  56. David

    August 12, 2019 , 7:45 am

    Just tried to edit my last comment, but no provision unfortunately.

    Only noticed the spelling error after posting. I meant to write ‘misapprehension’ rather than what I did write.

  57. Paul

    September 27, 2019 , 10:41 am

    I’m 66 and take between 1.5g and 2g of magnesium oxide per day before bed as a laxative. I am chronically constipated and would not like to be without this. I currently don’t supplement calcium, but from what I read here I guess you would advise it. I am a little concerned about taking calcium as I have read it can deposit on artery walls. As I am taking a magnesium “bolus” do you think 400mg calcium/day would do?

  58. Megan AlgaeCal

    October 1, 2019 , 9:49 am

    Hi Paul, thanks for reaching out!

    If you have low bone density, or would simply like to maintain bone health, AlgaeCal may be for you! AlgaeCal is different from most calcium supplements because it’s natural, plant-based, and does not cause calcium deposits in soft tissues such as your arteries. We added in vitamin K2 which helps transport calcium away from organs and into your bones! The safety of AlgaeCal is demonstrated in our 3 human clinical studies here.

    – Megan @ AlgaeCal

  59. Mel

    March 25, 2020 , 3:27 am

    I know this is an old thread but I found it very interesting and switched to Mag Oxide. Now I have a new but related question.

    I have become very interested in adding silica to my diet for anti-aging. Have read dozens of studies about silica bioavailability. They all say that the various forms of silica tend to have a lot of bioavailability problems.

    Is it valid to measure bioavailability by urinary excretion? All the studies do this. Could urinary excretion be something undesirable? I want the silica to stay in my body and feed my joints and skin, not be excreted in urine.

    The studies always say that Silicon Dioxide powder is minimally bioavailable or not bioavailable at all. And the best bioavailability is from Orthosilicic Acid. Again, they are making these conclusions based on the amount of the substances that are excreted in urine. Is this perhaps totally wrong-headed?

    Is it possible we have a similar situation as with Magnesium Oxide? And in fact, Silicon Dioxide will get absorbed and made available to the cells, perhaps more slowly than other forms? But better overall?

    I hope Lara is still around and can address this question. Thanks.

  60. Lara Pizzorno

    March 31, 2020 , 5:35 pm

    Unfortunately, the “state of the art” in regards to evaluating how much of a mineral is effectively used in the body before excretion is far from optimal.

    Apparent absorption is determined using fecal or urinary excretion, and values are usually expressed as a percentage of intake.
    Here’s the formula used:
    Apparent absorption = intake – (total fecal excretion – total endogenous fecal excretion) divided by intake x 100
    Urine is a major pathway of excretion for some minerals – including silicon as well as magnesium, iodine and potassium – but a minor pathway for others such as manganese, iron, zinc and copper.

    Collecting urine during absorption studies allows net retention to be calculated, but probably has little value in determining bioavailability of a mineral element. In many situations, the mineral element excreted in the urine represents a portion that was potentially nutritionally effective and has been involved in, or was available for use in, metabolism. In such cases, it’s an error to include the urinary fraction as a part of the unavailable portion of total dietary intake.

    Functional assays for bioavailability are a better option but rarely used in consumer testing. In a functional assay, the level or activity of an essential compound in which the mineral element is a necessary component (e.g., iron for hemoglobin and cobalt for vitamin B12) are used. Measurements in tissues of selenium-dependent glutathione peroxidase levels and cytochrome C oxidase activity as influenced by copper have been used as indicators for bioavailability of these two elements. I don’t see anything similar for silicon.

    However, it is true that our kidneys eliminate minerals that are either (1) not in a bioavailable form (for example, are bound to phytate or, in the case of silicon, is not soluble in water, so is not bioavailable [as I think you know orthosilicic acid is the form of silicon that is soluble in water]) or (2) when we have consumed more of the mineral than can be absorbed at one time because all the mechanisms utilized for its absorption are saturated. An example here is calcium, whose fractional absorption rate drops when more than 500 mg is consumed at one time. Or strontium, which we do not absorb when consumed at the same time as calcium because both minerals use the same absorption pathways, and calcium is always preferentially absorbed over strontium, so saturates all available transporters.

  61. Mel

    April 6, 2020 , 10:52 am

    Thanks so much, Lara, for your very informative reply.

    I remember reading in one of the studies that urinary excretion is justified as a measure of nutrient bioavailability on the assumption that the body seeks equilibrium and so will dump excess nutrients in the urine. In some studies I saw, more silicon was excreted than was ingested in a few cases.

    If urinary excretion is a measure of the body’s seeking equilibrium, then there’s no point in taking high dose supplements because you just lose them in the urine, as the body doesn’t need them.

    But is it possible that the scientists have it completely wrong, and the opposite is the truth? That the forms of silicon or magnesium that produce the LEAST amount of urinary excretion are, in fact, the MOST bioavailable? Because the nutrient stays in the body and is not excreted into the toilet?

    They say there’s an inverse relationship with silicon content and absorption in most foods — banana has a lot of silicon but very little is measured in urine, so it is presumed to have low bioavailability. Other foods have very little silicon but apparent high absorption rates. If very little of banana silicon is eliminated in the urine, where does it go? Maybe it goes to the joints, skin and other areas that need it?

    From what you said, if you want the nutrient to stay in your body and not be excreted, is it reasonable to take smaller doses throughout the day, instead of a large amount all at once?

    I saw at least one reference that silicon dioxide powder CAN be absorbed if you add it to water.

    From EFSA, “Calcium silicate and silicon dioxide/silicic acid gel added for
    nutritional purposes to food supplements: Scientific Opinion of the Panel on Food Additives and Nutrient Sources added to Food.”

    “No data have been submitted on the bioavailability of silicon from either silicon dioxide or silicic acid gel. However, several studies have shown that silicon present under similar form was readily available from foods and in many cases showed absorption similar to that of silicon from liquids. Furthermore, given the conversion of silicon dioxide/silicic acid to orthosilicic acid upon hydration, and the bioavailability of silicon from orthosilicic acid, the Panel considers that silicon from silicon dioxide/ silicic acid gel is bioavailable.“

    And another from EFSA, “Re-evaluation of silicon dioxide (E 551) as a food additive”
    in EFSA Journal 16(1) · January 2018

    From abstract: “Silicon dioxide appears to be poorly absorbed. However, silicon-containing material (in some cases presumed to be silicon dioxide) was found in some tissues….”

    “Some studies reported that less than 0.5% of silicon orally applied as silicon dioxide (1,250 mg) was excreted via urine but urinary silicon was always within the range of normal physiological variation”

    I also saw one study that said SiO2 in nano form might cause intestinal problems.

    I also am not sure if what they are referring to is Si02 powder in its crystalline form or amorphous Si02 or Si02 gel.

    Do you have any thoughts on the best sources of bioavailable silica? I’ve been drinking bamboo leaf tea and eating bamboo shoots and non-alcoholic beer but I’m interested in the most efficient way to get large therapeutic amounts of Si into my body in order to discover if it’s a fountain of youth :o)

    If Silicon Dioxide is in fact bioavailable to a limited extent, it is far easier, and cheaper, to buy AR grade Silicon Dioxide powder and steep it in a jug of drinking water, maybe for an extended time.

    When I added Magnesium Oxide powder to drinking water, it tended to form crystals. But maybe some of it was absorbed in the water. I crunched the crystals with my teeth and ate them. I have no idea how much was absorbed.

    Thanks again for sharing your knowledge and opinions.

  62. peta fleming

    April 9, 2020 , 12:29 am

    Hi Joice, Do you think AlgaeCal would help with my cronic constipation? I have tried Magnesium oxide powder on its own and while I had more energy it actually made me more constipated. Would this product provide the magic I need to keep consuming magnesium oxide?
    Thanks Peta

  63. Blaire AlgaeCal

    April 9, 2020 , 2:48 pm

    Hi Peta,

    Thanks for reaching out! This is a great question. A customer asked a similar question in AlgaeCal’s Facebook Community, and Lara responded with this:

    “Constipation suggests either insufficient intake or impaired absorption of magnesium or insufficient intake of fiber and fluids. Take a look at your diet to see how much magnesium it’s providing for you (if you have a copy of Your Bones, you can use the Foods Rich in Magnesium table to get a quick estimate). Then take a look at how much calcium you are getting from your diet as well. You want to be consuming approximately twice as much calcium as magnesium (ideally, 1,200 mg of calcium daily, so 600 mg of magnesium daily). AlgaeCal Plus provides this balance for you but not the full amounts (AP contains 720 mg of calcium and 360 mg of magnesium), but you need to look at any other supplements you take and your diet to check that you are maintaining this 2:1 balance overall. If you find you are not, you can increase your consumption of magnesium-rich foods (best option) or consider taking a magnesium supplement (150 mg of magnesium citrate taken at bedtime usually does the job, although in your case, you may be better off avoiding citrate and taking a different magnesium salt instead, maybe magnesium L-threonate).

    Also check your fiber intake. Are you eating enough fiber-rich foods? Apples, for example, are excellent sources of fiber and not only fiber, but many beneficial phytonutrients that improve digestive and eliminative function. Here’s a link to more on the latest about apples: Another possibility is beans — particularly, black beans, which are very rich in fiber, also anthocyanins (a highly protective type of phytonutrient), protein, magnesium and trace minerals. Here’ a link to info on black beans: And of course, good old prunes, which are especially good for us because of their boron content and thus beneficial effects on our bones. Several papers since 2010 confirm benefit: Just one little word of caution – don’t “go bananas” about prunes and consume more than the 100 grams (~3 ounces) used in the studies or you may find yourself not only no longer constipated, but attached to your toilet. When I was in college (MANY years ago now!), one of my roommates tended to become constipated — a problem that was completely solved by eating prunes or drinking a glass of prune juice instead of orange juice with breakfast. We (my other roommates and I) gave her a pin that said “Prune juice will set you free!” Liberation is GREAT, but in this case, too much liberation is not what we want!

    Lastly, you may want to try taking P5P (this is the activated form of B6 and the form in which B6 helps us absorb magnesium). At least 1 in 4 people have a genetic inheritance that makes them less able to activate B6 to P5P and thus do not do a great job of absorbing magnesium. P5P is inexpensive, readily available and safe. You can try taking 1 capsule daily (supplements typically contain P5P in a dose of 50 mg per capsule, which should be sufficient.)”

    We hope you find this information helpful, Peta! Please let us know if you have any questions ?

    – Blaire @ AlgaeCal

  64. peta fleming

    April 9, 2020 , 12:49 am

    So sorry, that should have been Hi Lara! !!!!

  65. Saleha

    June 20, 2020 , 10:56 am

    Hi. I’m thinking of trying Magnasium oxide 250 mg everyday (Nature Made brand). I take 600mg Calcium carbonate everyday. I’m 26 yrs old woman. Is the magnasium enough for me?

  66. Blaire AlgaeCal

    June 23, 2020 , 2:44 pm

    Hi Saleha,

    Thanks for sharing! We do recommend consuming a 2:1 ratio of calcium to magnesium. However, we suggest taking a more body-friendly form of calcium. It’s important to take a plant calcium that provides your bone with a multi-mineral approach to healthy bones. You can learn more about the different types of calcium here.

    Hope that helps! Feel free to give our Bone Health Consultants a call at 1-800-820-0184 if you have further questions ?

    – Blaire @ AlgaeCal

  67. Pat Hegdal

    April 13, 2021 , 2:06 pm

    I have been taking algaecal for about year. I went in this past week for my bone density test. I went from osteoporosis to osteopenia in a years time. It is because of algaecal. I have taken magnesium citrate for years and I think it went to my veins and stayed,.because I developed high blood pressure.

  68. Megan AlgaeCal

    April 14, 2021 , 9:00 am

    Hi Pat!

    Congratulations on your bone density increases! 😀 We are so so very happy for you. We want to offer you the opportunity to share your story on our website and inspire others! If this is something you’d be interested in, please reach out to our team at 1-800-820-0184 and we’ll be happy to provide you with further details.

    We recommend reaching out to your doctor about your blood pressure, as there are several possible causes and magnesium typically helps to regulate blood pressure. ❤️

    Looking forward to hearing from you, Pat!

    -Megan @ AlgaeCal

  69. Joseph Zimmerman

    July 8, 2020 , 3:11 am

    I’m curious regarding Lara’s thoughts on this research paper which concluded “Mg oxide supplementation resulted in no differences compared to placebo.”

    Mg Citrate Found More Bioavailable Than Other Mg Preparations in a Randomised, Double-Blind Study

    Published data on the bioavailability of various Mg preparations is too fragmented and scanty to inform proper choice of Mg preparation for clinical studies. In this study, the relative bioavailability of three preparations of Mg (amino-acid chelate, citrate and oxide) were compared at a daily dose of 300 mg of elemental Mg in 46 healthy individuals. The study was a randomised, double-blind, placebo-controlled, parallel intervention, of 60 days duration. Urine, blood and saliva samples were taken at baseline, 24 h after the first Mg supplement was taken (‘acute’ supplementation) and after 60 days of daily Mg consumption (‘chronic’ supplementation). Results showed that supplementation of the organic forms of Mg (citrate and amino-acid chelate) showed greater absorption (P = 0.033) at 60 days than MgO, as assessed by the 24-h urinary Mg excretion. Mg citrate led to the greatest mean serum Mg concentration compared with other treatments following both acute (P = 0.026) and chronic (P = 0.006) supplementation. Furthermore, although mean erythrocyte Mg concentration showed no differences among groups, chronic Mg citrate supplementation resulted in the greatest (P = 0.027) mean salivary Mg concentration compared with all other treatments. Mg oxide supplementation resulted in no differences compared to placebo. We conclude that a daily supplementation with Mg citrate shows superior bioavailability after 60 days of treatment when compared with other treatments studied.

  70. Lara Pizzorno

    July 10, 2020 , 11:11 am

    Thank you, Joseph! Great question.

    The fact that this type of research is still being used to assert Mg oxide is not as effective as Mg citrate shows a lack of understanding of magnesium’s use in the body.

    The optimal outcome of Mg absorption and bioavailability studies would be an increase in RBC Mg.
    You do not want Mg to increase in saliva or serum or to increase in urine! You want levels to increase inside cells. That is where Mg does its work for us.

    Studies that show Mg oxide appears at far lower levels in serum or urine actually support the fact that Mg oxide’s slower rate of release and absorption along the full length of the intestinal tract results in improved uptake into cells.

    Mg is absorbed into cells with the help of certain transporter molecules and P5P, the activated form of B6. When available transporters are saturated, as they will be by Mg salts that rapidly disassociate, like Mg citrate, none will be available to transport more Mg where it belongs – inside our cells. So, the overabundant load of Mg ions rapidly released from Mg citrate, which cannot be absorbed because transporters are fully already occupied, will be sent into the bloodstream and then quickly cleared via the kidneys and eliminated in urine. So levels in blood and urine will go up.

    On the cell surface, TRPM6/TRPM7, MagT1, and CNNM family have been demonstrated to facilitate magnesium influx into the cell, while SLC41A1 mediates magnesium efflux. In cytoplasm, PI3K/Akt/mTOR is magnesium-sensitive. Activation of this signaling cascade by intracellular magnesium is essential for cell growth, proliferation as well as the inhibition of autophagy. CNNM, cyclin M; MagT1, magnesium transporter 1; SLC41A1, solute carrier family 41 member; TRPM6/TRPM7, transient receptor potential melastatin type 6 and 7.

    And here’s another more recent paper showing renal excretion of Mg oxide is lower than that of Mg citrate.

    Again, this is a positive – for Mg oxide — outcome!

    And is precisely what I was trying to explain in my article comparing various forms of magnesium. Higher urine levels of Mg from a Mg salt indicate more Mg is being eliminated, not used in the body.

    Higher blood levels of Mg indicate Mg is not being absorbed effectively into cells, which is where 99% of the body’s magnesium is found. ~1% of Mg is in the bloodstream. This is why a serum Mg tells you virtually nothing and an RBC Mg (the amount of Mg inside red blood cells) is necessary.

    What should have been done in both the study you asked about and this later study was a comparison of RBC Mg after supplementation with Mg oxide and Mg citrate.

    Again, thanks for a great question! I’m sure others see such research and wonder what it means re Mg oxide.

    Stay well,


  71. Joseph Zimmerman

    July 11, 2020 , 12:44 am

    Thank you so much Lara for your detailed and very informative response!

    Forgive me for this follow-up question, but how can we be sure that the ingested Mg oxide is not mostly “passing through” our intestinal tract and getting excreted in the feces? Couldn’t that be a potential explanation for Mg oxide’s far lower levels in the serum or urine?

  72. Rueben Jiminez

    July 20, 2020 , 5:25 pm

    I have been taking 400 mgs daily of chelated mag glycinate. It has really helped my depression and anxiety along with my glucose levels. One problem, bad constipation! Can you suggest another mag that can give me the benefits without the constipation please.

  73. Megan AlgaeCal

    July 21, 2020 , 3:06 pm

    Hi Rueben,

    Glad to hear that magnesium glycinate has helped with your depression, anxiety, and glucose levels! We would recommend checking in with your doctor or a natural health practitioner about the type of magnesium that would be best for you. It’s important to consider your medical history, current health status, and medication/supplement regimen.

    You can search for certified functional medicine doctors in your area using this link.

    Hope this helps! ❤️

    -Megan @ AlgaeCal

  74. Castro

    September 11, 2020 , 10:25 am

    Hello, there ,I would love to know your opinion regarding various studies that have highlighted the significant toxic damage of MGOxide and other Oxide nano particles on DNA genome and human cells. –

  75. Lara Pizzorno

    September 14, 2020 , 8:11 am

    Hi Castro,

    MgOxide nanoparticles are not present in plant foods containing magnesium oxide or in supplements containing magnesium oxide. MgOxide nanoparticles are highly reactive compounds synthesized for use in industrial applications.

    You can cross this one off your list of things to be worried about.

    Be well, Lara

  76. M. Valentijn

    October 7, 2020 , 3:51 am

    Hi lara,
    I was wondering if you know what the indication on supplement labels actually sais.
    If the label states that one dose or tablet contains 100 mg of magnesium, is this 100 mg of magnesium salt or 100 mg of magnesium only?
    So would there be MgO in the supplement, is there 100 mg of magnesium in one 100 mg dose or 60 mg?


  77. Megan AlgaeCal

    October 13, 2020 , 10:16 am

    Hi Miranda, that’s a great question!

    This can vary between labels. One way to know how much actual magnesium there is, is to look for the word “elemental.” If the label states 100mg of elemental magnesium, this supplement contains 100mg magnesium.

    If the label states 100mg magnesium (as magnesium oxide), it should also contain 100mg magnesium.

    However, if the label says 100mg magnesium oxide, then it contains 100mg of the magnesium salt and in this case, only 60mg of elemental magnesium.

    Hope this helps! 🙂

    -Megan @ AlgaeCal

  78. Olivia Young

    October 8, 2020 , 4:00 am

    Thank you for your in-depth explanation about the bioavailability of various magnesium salts. It seems very thorough overall but doesn’t include a discussion of mag l-threonate.

    Since mag is involved in so many critical metabolic processes in the brain, I can’t help but wonder whether or not the advantages of mag l-threonate are substantive or more of a marketing ploy.

    What do you think?

  79. Megan AlgaeCal

    October 13, 2020 , 10:38 am

    Hi Olivia, great question!

    Lara actually goes over the research behind magnesium threonate in a response to Gaetane’s question below. If you use the search function and type in “Gaetane,” you should see Lara’s in-depth response below. Hope this helps 🙂

    -Megan @ AlgaeCal

  80. Jeremy Males

    March 27, 2021 , 11:53 am

    It crosses the blood barrier. that is one heck of a benifit. Full doze is 145 mg. It is very effective sleep aid.

  81. wallyGic

    November 17, 2020 , 12:35 pm

    i am so satisfacted. greetings wally

  82. wallyGic

    November 24, 2020 , 3:03 am

    i am so english is poor, sorry :). thx for approving my user greetings wally

  83. G. Allen

    February 8, 2021 , 12:00 pm

    Why can’t we just take pure elemental magnesium (Mg)?

  84. Blaire AlgaeCal

    February 9, 2021 , 3:15 pm

    Great question, G! Magnesium naturally exists in foods; however, when taking it as a supplement, the molecule must be bound with something else (such as oxide) to be stable.

    Hope that helps! Let us know if you have further questions 🙂

    – Blaire @ AlgaeCal

  85. Toomas

    February 18, 2021 , 12:27 pm

    Interesting article. So I need at least 3,12g Magnesium Oxide daily to get my daily magnesium?
    (420mg as RDA).

  86. Megan AlgaeCal

    February 23, 2021 , 10:43 am

    Hi Toomas!

    When the RDAs were established, they took into account bioavailability and absorption, though we aren’t sure about the specific numbers they used. You can read about this here. Keep in mind that the RDAs are defined as the “Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy people.” The best way to ensure that you meet your needs is to choose food and supplement sources that are highly bioavailable and effectively absorbed. As each person’s needs and digestive capacities are highly individualized, it can also be helpful to check nutrient levels through lab tests to ensure you’re meeting your needs.

    Hope this helps!

    -Megan @ AlgaeCal

  87. Argo

    February 20, 2021 , 7:40 am

    Magnesium Salts comparison table says I get 13.8 mg from 100 mg Magnesium Oxide. Recommended daily dose for man is 420 mg.
    So to get that from Magnesium Oxide I would need at least (420 * 100) / 13.8 = ~3 g Magnesium Oxide daily.

    Even more in case of other Magnesium Salts.
    ~8g MgCarbonate
    ~8g MgChloride
    8.4g MgL-lactate
    12.7g MgCitrate
    12.7g MgAspartate
    13.1g MgGlycinate
    36g MgGluconate.

    Did a web search, didn’t find any supplement providing such amount.

    Got something wrong or so things are?

  88. Megan AlgaeCal

    February 23, 2021 , 10:25 am

    Hi Argo, great question!

    When the recommended daily allowances (RDAs) were established, they took into account bioavailability and absorption, though we aren’t sure about the specific numbers they used. You can read about this in this article. Keep in mind that the RDAs are defined as the “Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy people.” The best way to ensure that you meet your needs is to choose food and supplement sources that are highly bioavailable and effectively absorbed. As each person’s needs and digestive capacities are highly individualized, it can also be helpful to check nutrient levels through lab tests to ensure you’re meeting your needs.

    Hope this helps!

    -Megan @ AlgaeCal

  89. Shawnie

    October 10, 2021 , 7:17 am

    Thank you for this article! My neurologist suggested that I start taking Magnesium Oxide. And the fact that it may aid in lowering blood pressure and heart rate is an added benefit for me.

  90. Kirby Johnson

    October 12, 2021 , 9:07 am

    Hi Shawnie,

    So happy to hear you found this information useful! Please feel free to continue exploring all the information available on our blog HERE. As always, don’t hesitate to reach out if you have questions!

    Kirby @ AlgaeCal

  91. Donna Skellchock

    October 16, 2021 , 11:46 am

    In all my reading, I have not seen a clear and concise explanation of taking 400 mg of magnesium oxide and knowing if it meets RDA? 13.8 absorption of magnesium oxide is the absorption per 100 mg. of MO. Therefore, 400 mg of MO yields only 55.2 mg. of MO absorption. Does this mean I need to take 600-800 mg. of MO to meet my daily requirement??? How much of the 600-800 mg of MO would be excreted??? How many mg. of Magnesium Oxide do I need to take, factoring in the percent absorbed and the amount excreted, to reach my RDA???? So confusing!!!! If most of the Magnesium Oxide is excreted, then isn’t taking 400 OTC mg too much? No one has really addressed the effectiveness of OTC MO. Plain English please! Thank you!! Great Blog. can I get an email copy?

  92. Kirby Johnson

    October 18, 2021 , 2:15 pm

    Hi Donna,

    We can definitely sympathize with your confusion! You can receive an email copy of the blog article by selecting the letter icon on the green task bar on the left hand side of the screen (directly below the twitter symbol and above the print icon). The calculations you’ve laid out are not a necessary step when determining your RDAs; when RDAs were established, they took into account bioavailability and absorption – you can read more HERE. The key thing to aim for is meeting nutrient recommendations through healthy foods… and adding good quality supplements when needed.

    It’s worth mentioning that the RDAs for magnesium (420 mg/day for men and 320 mg/day for women) do not properly balance the RDA for calcium, which is 1,200 mg per day for those over the age of 70. The optimal balance between calcium and magnesium for bone building is 2:1. So, we actually require 600 – 750 mg of magnesium daily when you’re supplementing with the appropriate amount of calcium. We encourage you to maintain this ratio with your diet and other supplements as well.

    We’re happy to provide any additional information or to speak on AlgaeCal Plus’ optimal balance of calcium and magnesium. Please feel free to reach out to any of our Bone Health Consultants at 1-800-820-0184 (USA & Canada toll-free) 5am – 4pm PST weekdays, 6am – 4pm PST weekends if you’d like to speak with us directly. If you’d rather, you can also send us an email at [email protected] for further support.

    – Kirby @ AlgaeCal

  93. Conor Neilly

    March 13, 2022 , 12:39 pm

    Awesome article

    I am confused as to how the % elemental magnesium has been adapted from the ranade2001 paper?

    i cant make sense of the” Elemental Mg++/
    dose, mg (mEq)” row

  94. Kirby Johnson

    March 14, 2022 , 4:28 pm


    Thanks so much for following up with your question. Rather than utilizing the Elemental Mg++/
    dose, mg (mEq)e row, we used the 4th row (oral absorption %) as data points for our article. If you have any other questions, don’t hesitate to let us know!

    – Kirby @ AlgaeCal

  95. mitunssam

    May 10, 2022 , 9:40 pm

    ich hatte Recht 🙂 mituns

  96. Vic

    August 23, 2022 , 6:32 am

    Thank you for this very informative article with linking studies.

  97. Kirby Johnson

    August 23, 2022 , 10:23 am


    We’re so pleased to hear you enjoyed our content! If you ever have any further interest, you can always find more bone-health information on our blog HERE. It’s chock-full of delicious recipes, bone-strengthening exercises, and expert advice from industry professionals <3

    - Kirby @ AlgaeCal

  98. David Mörl

    October 26, 2022 , 3:12 am

    Hello, I have a question for you about this article
    I am wondering where the author got the information that is given in the first table Comparison of Magnesium Salts.
    In particular, I am interested in the information in the % Elemental MG Absorbed column. There are completely different values listed than are commonly reported on the internet. For example, for Citrate, the bioavailability is commonly quoted as 80 to 90% absorption. However, the table only states 30%. The same applies to Glycinate. It is also quoted at around 80% and the table only states 23%.

    Thank you in advance for your early reply, or please contact the author of the article. Sincerely, David Mörl

    Translated with (free version)

  99. Chelsea Dugas

    October 31, 2022 , 6:48 am

    Thanks for your question, David!
    Our resident Bone-Health Expert, Lara Pizzorno, provided this response for you:

    “Please let David know that the information provided in the post is taken from the papers cited as references. Here are links to the sources of my data, all peer-reviewed articles published in respected PubMed-listed journals, should he wish to confirm that it was correctly reported:
    If he would like to send me the papers to which he is referring, I can check them for accuracy.”

    Hope this helps and let us know if you have any more questions! 🙂

    – Chelsea @ AlgaeCal

  100. John

    November 2, 2022 , 3:27 pm

    In your July 10, 2020 comment you stated that,
    “You do not want Mg to increase… in urine! …
    Studies that show Mg oxide appears at far lower levels in serum or urine actually support the fact that Mg oxide’s slower rate of release and absorption along the full length of the intestinal tract results in improved uptake into cell.”

    But your article paragraph on Firoz’s paper says,
    “More magnesium excreted in the urine is thought to indicate that more magnesium has been absorbed; less magnesium excreted is thought to indicate that less magnesium has been absorbed. ”

    Are you saying that above quote is generally accepted belief? And that you believe less Mg excreted in urine is evidence of more absorption?

  101. Shelby AlgaeCal

    November 8, 2022 , 7:37 am

    Hi John,

    Thank you for reaching out with your questions! We apologize for the delay in getting back to you – this information is a little outside of our scope of knowledge, so we reached out to Lara Pizzorno, bone health expert, directly for information to answer your question! She has provided a very detailed response, and we have sent it to you as an email. We hope this helps! 🙂

    – Shelby @ AlgaeCal

  102. Suzette de jongh De jongh

    December 29, 2022 , 11:31 am

    want to no more about the product

  103. Shelby AlgaeCal

    December 29, 2022 , 12:47 pm

    Hello Suzette,

    Thank you for your interest in our products – it’s great to hear that you’d like to learn more, and to start you can click HERE to read about all of our supplements!

    Of course, if you’d like to know something specific or have any questions at all, our Bone Health Consultants would love to assist you over the phone or by email! You can reach us toll-free at 1-800-820-0184, or can send an email to [email protected]. We look forward to hearing from you! 🙂

    – Shelby @ AlgaeCal

  104. Malva Cohen

    January 31, 2023 , 9:43 am

    Will it work well to take P-5-P as part of a B complex designed with all the B Vitamins in it having better bioavailability, instead of P-5-P taken separately from the other B vitamins?

  105. Chelsea Dugas

    February 6, 2023 , 7:14 am

    Great question, Malva!
    The P5P in a B complex would be ok, however, the recommended dose would be to get at least 50 mg of P5P with your first dose of AlgaeCal Plus in the day (because P5P is a natural stimulant), and it may be challenging to find a B complex containing enough P5P in a daily dose to actually help. Hope this answers your question!

    – Chelsea @ AlgaeCal

  106. Charlespalding

    March 10, 2023 , 4:05 am

    Thanks, After I bought Mg Oxide I saw videos of people saying it’s a waste of money. Sounds like they are misleading people.

  107. Chelsea Dugas

    March 13, 2023 , 8:43 am

    Hi, Charles! We’re glad to know our article was helpful and you didn’t waste your money! Let us know if you have any questions.

    – Chelsea @ AlgaeCal

  108. Brandy Williams

    March 13, 2023 , 2:48 am

    How can we be sure that the ingested Mg oxide is not mostly “passing through” our intestinal tract and getting excreted in the feces? Couldn’t that be a potential explanation for the far lower magnesium levels in the serum and urine when supplementing with Mg oxide (when compared to supplementing with Mg citrate)?

  109. Brianne AlgaeCal

    March 14, 2023 , 10:37 am

    Hi Brandy,

    Thanks for commenting! As mentioned in the article, in a study involving 18 men, 24 hours after consumption of magnesium oxide supplements, magnesium levels in the urine increased about two times the normal amount. And, after 48 hours, magnesium levels had increased to roughly four times normal. The conclusion drawn by the researchers: these results clearly show that “magnesium oxide is effectively absorbed and elevates the biologically-active levels of magnesium in the bloodstream.”

    I hope this helps! 🙂

    – Brianne @ AlgaeCal

  110. Sherie Scheer

    April 4, 2023 , 3:48 pm

    What B complex do you recommend? I want one with low Niacin.

  111. Megan Khera

    April 5, 2023 , 10:23 am

    Thanks for reaching out, Sherie! While we don’t have a particular recommendation for a B-complex, feel free to give our Bone Health Consultants a call at 1-800-820-0184 (USA & Canada toll-free). They’ll be happy to work with you to determine your supplementation needs 🙂

    – Megan @ AlgaeCal

  112. Dan Rankin

    July 2, 2023 , 5:18 am

    Wow, what a well written article. I feel like I learned something. Thank you!

    My interest is in the binding of phytate. While it’s true that phytate makes minerals insoluble, it’s also true that most high magnesium foods contain lots of fiber, phytates, oxalates, and other things that effect the rate of magnesium absorption. Surely the amount of magnesium in a cup of lima beans would overwhelm the accompanying phytate’s ability to interfere.

    I’ve only ever seen the argument for phytate interference as a theoretical one. It seems unlikely that nature would be sabotaging us with these so-called anti-nutrients to any meaningful degree. If anything, they most likely maximize absorption by slowing everything down during transit. I’d love to know if anyone has any knowledge as to the actual effect on mineral absorption based on the phytate levels found in common high-mineral foods.

    Also, when it comes to Mg absorption studies, urine output is not particularly an accurate measure. The percentage of Mg retained by the kidneys can vary wildly between two people on the same supplement protocol due to the body demand for Mg at the time of testing. Just my thoughts though. Thanks again for the good read.

  113. Brianne AlgaeCal

    July 3, 2023 , 1:54 pm

    Hi Dan, thanks so much for your detailed comment. You certainly bring up some interesting points about phytates, and you’re on the right track! In fact, we have a detailed blog article about this very thing that I think you’ll enjoy – you can find it HERE! 🙂

    Additionally, thank you for your insightful comment on magnesium and urine output, and we’ve passed along this feedback to the author!

    – Brianne @ AlgaeCal

  114. Womp womp

    January 6, 2024 , 2:43 am

    you do realize that you absorb magnesium oxide at about 4% , so taking more wouldn’t do much you’re just taking more. If you take 100mg of magnesium oxide and you only absorb 4% you’ll only get 4mg for that 100mg, so base it off of that. Use a different form of magnesium, we don’t absorb magnesium oxide well so it’s best to use a different form

  115. Yoori AlgaeCal

    January 8, 2024 , 5:18 pm

    Thank you for sharing your feedback! While magnesium oxide is not as soluble as some other magnesium salts (and so it is not absorbed as rapidly in our body), magnesium oxide contains nearly triple the amount of actual magnesium (elemental magnesium) than other forms. This is why even with the lower absorption rate, it still delivers more magnesium per capsule so more gets into your bloodstream to deliver all its many benefits to your bones and body. For more details, please refer to section “Why Magnesium Oxide Provides More Elemental Magnesium” in this blog article :). Of course, if you have any follow-up questions, please give us a call at 1-800-820-0184 (US & Canada Toll-free) or email [email protected]. We are happy to help!

    – Yoori

  116. Jane

    April 8, 2024 , 2:34 pm

    I’m very sensitive to magnesium and it causes bloating, gas and diarrhea. Does this product cause such side effects?

  117. Yoori AlgaeCal

    April 9, 2024 , 2:53 pm

    Thank you for reaching out, Jane! Bloating, gas, and diarrhea can be caused by an imbalance in your Calcium to Magnesium intake. You see, too much magnesium can act as a natural laxative. AlgaeCal Plus contains naturally-occurring magnesium from the algae, and then we add additional magnesium oxide for an optimal 2:1 calcium to magnesium ratio! This mimics the ratio naturally occurring in your body, and we would not expect AlgaeCal to cause such discomforts :).

    With this said, we understand that nutrition can be complex and some people may be sensitive to higher levels of vitamin and mineral intake. For this reason, we provide our Risk Free Returns Policy, where we are happy to refund any unopened and partially used bottles within a year of your purchase date if you are not satisfied with our products for any reason. I hope this helps! 🙂

    – Yoori

  118. DK

    April 30, 2024 , 3:37 pm

    An oxide is NOT a salt.

  119. Yoori AlgaeCal

    May 1, 2024 , 5:34 pm

    Thank you for sharing, DK! I’d be happy to share this feedback with our team. We truly appreciate it!
    – Yoori

This article features advice from our industry experts to give you the best possible info through cutting-edge research.

Lara Pizzorno
MDiv, MA, LMT - Best-selling author of Healthy Bones Healthy You! and Your Bones; Editor of Longevity Medicine Review, and Senior Medical Editor for Integrative Medicine Advisors.,
Dr. Liz Lipski
PhD, CNS, FACN, IFMP, BCHN, LDN - Professor and Director of Academic Development, Nutrition programs in Clinical Nutrition at Maryland University of Integrative Health.,
Dr. Loren Fishman
MD, B.Phil.,(oxon.) - Medical Director of Manhattan Physical Medicine & Rehabilitation and Founder of the Yoga Injury Prevention Website.,
Prof. Didier Hans
PHD, MBA - Head of Research & Development Center of Bone Diseases, Lausanne University Hospital CHUV, Switzerland,