The Surprising Benefits of Unabsorbed Calcium In Your Digestive Tract

Updated: May 8, 2020

Lara Pizzorno is the author of “Your Bones: How You Can Prevent Osteoporosis and Have Strong Bones for Life – Naturally” and a member of the American Medical Writers Association with 29 years of experience specializing in bone health.

Recently we asked Lara if she would help us provide a series of short, ongoing videos to help you (our customers and readers) stay up to date on the latest facts and science related to bone health.

In this latest video, Lara talks about the benefits of unabsorbed calcium in your digestive tract and how it may reduce your risk of colorectal cancer. Watch the video below (or read the transcript provided) and let us know what you think in the comments. 🙂

Hello, I’m Lara Pizzorno the author of “Your Bones” and I’m here today to share information with you that I hope will help you have healthier bones.

In our last video clip we talked about how much calcium you should take at one time to get the best absorption from a calcium supplement and that amount turned out in the research to be 350 mg per dose and then about 720 or so per day but you want to break that amount up into about 350 mg per dose.

And in the research that showed that this was beneficial, it showed that you were absorbing about 36% of the elemental calcium when you took the 350 mg per dose.

And so I asked you to consider what was happening to the rest of that calcium, the 64% of calcium that then passed out through the digestive tract, whether it served you, whether it did anything for you.

In this video I would like to explain to you some of the benefits that that unabsorbed elemental calcium provides for your body.

Calcium remaining in food residue or from supplements that you take actually combines in your intestines with harmful substances that are left over from digestion such as oxalic acid or unabsorbed fatty acids and bile acids and this is the mechanism through which high calcium diets actually reduce our risk of kidney stones and cancer, because that calcium combines with potentially harmful substances and puts it in stool so that it is evacuated from your body.

There’s a bunch of studies that confirm some of these benefits and I’d like to share with you some information about two of them. One about cancer and one about kidney stones.

The first one I’d like to talk with you about was published in 2014 and they looked at 41,403 participants in this health study who ranged from 20-60 years.

And what they found, was that women who had low intakes of calcium, less than 500 mg per day or even as much as 700 mg of calcium per day had a much greater risk of multiple and advanced colorectal adenomas, in other words colon cancers.

I’m going to post the references along with this video on AlgaeCal’s website so if you’re interested in this research you’ll be able to go on PubMed and find this study.

The other study I’d like to talk to you about is one where they looked at kidney stone formation and calcium consumption was beneficial for kidney stone recurrence. That is what they found, they did a Cochrane review, which is the standard of reviews for the medical literature and they looked, they published it in February of last year, 2014, and they looked at people with the term idiopathic hypercalciuria, which simply means that they were forming kidney stones and the researchers or doctors didn’t know why.

So they found 5 studies that looked at people with this problem and every single one of those studies showed a significant decrease in the numbers of new stone formation in those people who were treated with calcium, normal calcium intake so optimal is 12- 1500 mg per day of calcium and a low protein, low salt diet and they showed 28% decrease in new stone formation with good calcium intake.

So all the calcium that we consumed was absorbed by the intestines we would meet our body’ skeletal needs for calcium but would not provide for this very important detoxification function that unabsorbed calcium serves within the intestinal lumen itself.

So unabsorbed calcium is going to help you prevent kidney stone formation and colorectal cancer.

To sum up from the last couple of videos and you want to get the best bang from your calcium supplement buck:

  • You want to take your calcium with a little bit of food even a small snack will cause your stomach to produce hydrochloric acid that is required for the optimal absorption of any calcium you are taking
  • Then you want to take your calcium in a dose of about 350 mg twice a day
  • And you want to ensure your blood levels of vitamin D are in the optimal range of 50-80 nanograms per ml.
I’d like to talk with you next time about calcium fortified beverages and whether these are a good source of supplemental calcium to be relied upon to meet your calcium needs.

Thanks for tuning in!


Massa J, Cho E, Orav EJ, Willett WC, Wu K, Giovannucci EL. Total calcium intake and colorectal adenoma in young women. Cancer Causes Control. 2014 Apr;25(4):451-60. doi: 10.1007/s10552-014-0347-9. Epub 2014 Feb 22. PMID: 24562904 (I usually only list the first 3 authors, but Willet and Giovannucci are friends of ours and legends in the field, so I wanted to include their names in our listing)

Escribano J, Balaguer A, Roqué i Figuls M, et al.  Dietary interventions for preventing complications in idiopathic hypercalciuria. Cochrane Database Syst Rev. 2014 Feb 11;2:CD006022. doi: 10.1002/14651858.CD006022.pub4. PMID: 24519664

Heaney RP. Factors influencing the measurement of bioavailability, taking calcium as a model. J Nutr. 2001 Apr;131(4 Suppl):1344S-8S. PMID: 11285351

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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,