3 Great Ways to Boost Your Vitamin D This Winter

Updated: October 5, 2023

As the winter months roll in, we’re all getting ready to hunker down a bit and spend more time with our indoor activities and less time outside. While this time of year can offer an excellent opportunity to slow things down and become more introspective, there is one very significant downside to spending less time outside – lack of vitamin D. 

In fact, research shows that due to the latitude of certain areas in the Northern US, sun exposure during the months of November to February results in zero vitamin D synthesis, even on completely cloudless days [1][2]. 

And while you may be able to get some vitamin D from foods, sunlight is far superior to food, making it the best way to help your body synthesize vitamin D. Among its many duties, vitamin D is essential for the proper utilization of calcium and phosphorus, two minerals that are vital to bone health. 

This means that when your vitamin D is low, it can set the stage for bone diseases like osteomalacia and osteoporosis [3][4]. 

So, how can you enjoy the winter months without worrying about your vitamin D status?

In this article, you’ll learn:

  • Why sunlight is so crucial for vitamin D synthesis
  • The optimal level of vitamin D that you should aim for
  • The best ways to optimize vitamin D production in the winter
  • How to supplement with vitamin D to maintain the health of your bones

Vitamin D And Sunlight

Vitamin D is a unique nutrient in that a healthy, well-balanced diet isn’t enough to keep its levels high. Unlike most nutrients that are absorbed and assimilated through your diet, vitamin D is primarily synthesized through your skin with the help of sunlight. 

When your skin is exposed to UVB rays from the sun, a compound called 7-dehydrocholesterol absorbs the rays and is converted to vitamin D3. This is just one of the fascinating ways in which your body shows you how highly in tune you are with your environment [5].

Your ancestors lived their lives very close to the earth, communing with the natural world. They would spend the majority of their time outdoors, even in the colder winter months. Today we get to enjoy the luxuries of modern life, which is lovely for many reasons, but it also puts us at risk for vitamin D deficiency.

That said, studies show that just 10-15 minutes of daily sunlight exposure in summer and spring can produce enough vitamin D to meet your needs [6][7]. Of course, several factors can influence your body’s synthesis of vitamin D from sunlight, including season, time of day, latitude, altitude, air pollution, skin pigmentation, level of body fat, and aging [5][8].

While asking you to spend more time outside in the chill of the winter may be a non-starter, luckily, we have modern solutions to our modern conundrum. But before we jump into the best ways to enhance vitamin D synthesis in the winter, let’s review what optimal levels should look like and how you can test to ensure you’re on track.

How To Test And Determine Your Optimal Levels of Vitamin D 

The best test for measuring vitamin D levels is the 25-hydroxy vitamin D test, which your doctor can order. This is a simple blood test that will tell you how much vitamin D is in your circulation and give you an indication of whether you need to increase vitamin D synthesis.

What Is The Optimal Level of Vitamin D?

There is some debate about the optimal level of vitamin D in the blood.

For example, some experts suggest aiming for 30-50ng/mL while a study from the Boston University School of Medicine found a range of 40-60 ng/ml was needed to achieve the full range of health benefits conferred by vitamin D [11][12].

Another study from the University of California found that a higher range of 60-80 ng/ml was associated with a significantly reduced cancer risk [13].

Ultimately, your optimal levels will depend on your current health status and health goals. 

When it comes to supplementing with vitamin D, the National Institute of Health recommends that adults under 71 need 600 IU daily, with that number increasing to 800 IU for adults over the age of 71. However, this dosage may be a bit conservative as The International Osteoporosis Foundation recommends a higher dose of 800-1000 IU a day for adults over the age of 60. Furthermore, the Endocrine Society recommends 1500-2000 IU per day for all adults [14][15].

What Are the Symptoms Of Low Vitamin D?

According to an NHANES study, 40% of adults in the United States are vitamin D deficient [15].  And that number increases for people over the age of 65, especially postmenopausal women [9][17].

While a blood test is the gold standard for determining vitamin D levels, you may also want to pay attention to your body for signs of low vitamin D. 

Some symptoms of low vitamin D include [10]: 

  • Muscle pain
  • Bone pain
  • Increased sensitivity to pain
  • Tingly, “pins-and-needles” sensation in the hands or feet
  • Muscle weakness in the upper arms or thighs
  • Waddling while walking due to muscle weakness in the hips or legs
  • Easily broken bones
  • Muscle twitches or tremors
  • Muscle spasms

What Happens When You Have Too Much Vitamin D In Your System?

Conversely, it’s also possible that you have too much vitamin D, although this is much less common and typically results from over-supplementation. Generally speaking, you would have to consume amounts much higher than what you’d find in daily supplements. For example, taking around 60,000 IU of vitamin D daily for several months has been shown to cause vitamin D toxicity [16].

When you have too much vitamin D in your system, it causes a buildup of calcium in your blood which can create a range of symptoms, including:

  • Nausea
  • Vomiting
  • Weakness
  • Frequent urination 
  • And ultimately could progress to the formation of calcium stones

Can You Get Enough Vitamin D from Your Diet?

While a handful of foods contain vitamin D, even choosing highly fortified foods is not enough to keep your vitamin D levels in a healthy range. For example, 3.5 ounces of wild-caught salmon may contain around 988 IU of vitamin D, and vitamin D fortified milk contains around 100-150 IU [18][19].

As mentioned, this is a unique nutrient that humans have historically received primarily through sunlight.

Although the winter months are a time of year when you likely spend more time indoors, in modern society, it’s rare that anyone is getting enough vitamin D from food or sunlight alone (especially if you live in an area where you aren’t getting sunlight all year). This is why supplementing with vitamin D has become such a crucial part of healthy aging. 

Best Vitamin D Supplements To Take During The Winter

Even if you’re young and highly active outdoors, you still likely need a vitamin D supplement for the winter months. 

There are hundreds of different vitamin D supplements out there, so when choosing the option that’s right for you, keep in mind:

  • You’ll want a supplement with a dose of 600 IU at the minimum. 
  • You’ll want to see vitamin D3 (cholecalciferol) on the label. There are several different forms of vitamin D, and many supplement companies use vitamin D2, which isn’t as well absorbed or as effective as D3.

AlgaeCal products use vitamin D3 (cholecalciferol), with AlgaeCal containing 1000 IU of vitamin D3 and AlgaeCal Plus containing 1600 IU. Moreover, these products come packed with other bone-building nutrients that all work together synergistically. 

Cofactors Needed To Optimize Your Vitamin D Function

In addition to getting enough vitamin D itself, there are several nutrients that serve as cofactors for vitamin D utilization.

These include magnesium, boron, zinc, vitamin A, and vitamin K.

  • Magnesium is required to activate vitamin D and transport it around in your blood[20]. 
  • Boron supports vitamin D utilization, with studies showing that it can specifically enhance the impact of vitamin D on bone health[21]. 
  • Zinc plays a role in vitamin D dependent genes, and studies show that low zinc levels predict vitamin D deficiency[22]. 
  • Vitamin A has a synergistic relationship with vitamin D, making the balance of these two nutrients crucial[23]. 
  • Much like vitamin A, vitamin D and vitamin K also have a synergistic relationship which particularly seems to impact bone and heart health[24].

Top 3 Ways to Get Enough Vitamin D in the Winter

#1 Get Outside (When You Can)

Yes, the winter is cold – but with an extra scarf or a puffier jacket, you can still make it out for some outdoor activities now and then. Trying to get outside for a walk several times a week will do wonders for your mental health, as well as help boost your vitamin D. 

Pro Tip: The more sun exposure on your skin, the better, so if you’re walking and start to get warm, roll up those sleeves to get some sunlight on your arms.

#2 Incorporate More Vitamin-D Rich Foods

There are several foods that contain a fair amount of vitamin D that you can try to incorporate more of during the winter months.

For example, 3.5 ounces of wild-caught salmon contains around 988 IU of vitamin D, and a 3.5-ounce can of sardines contains 272 IU. Other seafood options that offer a rich source of vitamin D include oysters, tuna, and shrimp.

For the vegetarians out there, mushrooms and eggs are also sources of vitamin D.

#3 Take a High-Quality Supplement

At the end of the day, having a high-quality vitamin D supplement is your fail-safe during the winter months. While it is an excellent idea to get outside and experience some natural sunshine during the winter, the number of hours you would have to spend outside (with your skin exposed) to achieve optimal vitamin D levels is unreasonable for most people. 

And even if you stock up on vitamin D during the summer, it’s unclear how much of this becomes available for use in the winter [25].

Likewise, boosting your diet with extra vitamin D is always a good idea, but it’s unlikely to get you to where you need to be. 

To avoid the potential downfalls of low vitamin D, provide yourself with a supplement that will keep your body and bones healthy and thriving throughout the winter months. 


As the winter sets in, let this season be a time of peace and relaxation. Get ready for some cold nights by the fire, dig into a good book or hobby that helps you feel grounded, get outside when it feels comfortable, and stock up on some delicious vitamin D-rich foods. 

For the rest of your vitamin D needs, know that you’re taking care of your body by providing it with the nutrients it needs through high-quality supplementation.


Can I get vitamin D from the sun in winter?

Depending on where you live, you may be able to get vitamin D from the sun in the winter. However, research shows that due to the latitude of certain areas in the Northern US, sun exposure from November to February results in zero vitamin D synthesis, even on completely cloudless days.

How can I increase my vitamin D in the winter?

The best way to get vitamin D is through sun exposure. However, a high-quality vitamin D supplement is an excellent option if you live in a latitude that prevents vitamin D synthesis from the sun.

How much vitamin D should I take during winter?

Since it’s unclear how much vitamin D can be stored from summertime sun exposure, you’ll want to supplement with a dose of 600 IU at the minimum. 

What is the best way to absorb vitamin D?

Several cofactors can help you absorb and utilize vitamin D when you take it as a supplement. These include magnesium, boron, zinc, vitamin A, and vitamin K.


  1. Webb, Ann R., Loren Kline, and Michael F. Holick. “Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.” The journal of clinical endocrinology & metabolism 67.2 (1988): 373-378./
  2. Holick, Michael F. “Vitamin D: a d-lightful solution for health.” Journal of investigative medicine 59.6 (2011): 872-880.
  3. Minisola, Salvatore, et al. “Osteomalacia and vitamin D status: a clinical update 2020.” JBMR plus 5.1 (2021): e10447.
  4. Lips, Paul, and Natasja M. Van Schoor. “The effect of vitamin D on bone and osteoporosis.” Best practice & research Clinical endocrinology & metabolism 25.4 (2011): 585-591.
  5. Wacker, Matthias, and Michael F. Holick. “Sunlight and Vitamin D: A global perspective for health.” Dermato-endocrinology 5.1 (2013): 51-108.
  6. Religi, A., et al. “Estimation of exposure durations for vitamin D production and sunburn risk in Switzerland.” Journal of exposure science & environmental epidemiology 29.6 (2019): 742-752.
  7. Gani, Linsey Utami, and Choon How How. “Vitamin D deficiency.” Singapore medical journal 56.8 (2015): 433.
  8. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
  9. https://my.clevelandclinic.org/health/diseases/15050-vitamin-d-vitamin-d-deficiency
  10. https://www.yalemedicine.org/conditions/vitamin-d-deficiency 
  11. https://endocrinenews.endocrine.org/april-2014-boning-up-on-osteoporosis/
  12. Grant, William B., et al. “A narrative review of the evidence for variations in serum 25-hydroxyvitamin D concentration thresholds for optimal health.” Nutrients 14.3 (2022): 639.
  13. Garland, Cedric F., et al. “Vitamin D supplement doses and serum 25-hydroxyvitamin D in the range associated with cancer prevention.” Anticancer Res 31.2 (2011): 607-611.
  14. https://www.osteoporosis.foundation/vitamin-d-recommendations
  15. https://cancer.ca/en/cancer-information/reduce-your-risk/eat-well/eating-well-extras-to-consider
  16. Parva, Naveen R., et al. “Prevalence of vitamin D deficiency and associated risk factors in the US population (2011-2012).” Cureus 10.6 (2018).
  17. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108
  18. Capatina, Cristina, et al. “Vitamin D deficiency in postmenopausal women–biological correlates.” Maedica 9.4 (2014): 316.
  19. Lu, Z., et al. “An Evaluation of the Vitamin D3 Content in Fish: Is the Vitamin D Content Adequate to Satisfy the Dietary Requirement for Vitamin D?” J Steroid Biochem Mol Biol (2007): 642-644.
  20. https://www.usdairy.com/news-articles/what-type-of-vitamin-d-is-in-milk
  21. DiNicolantonio, James J., and James H. O’Keefe. Magnesium and vitamin D deficiency as a potential cause of immune dysfunction, cytokine storm and disseminated intravascular coagulation in COVID-19 patients.” Missouri medicine 118.1 (2021): 68.
  22. Pizzorno, Lara. “Nothing boring about boron.” Integrative Medicine: A Clinician’s Journal 14.4 (2015): 35.
  23. Amos, Ashton, and Mohammed S. Razzaque. “Zinc and its role in vitamin D function.” Current Research in Physiology (2022).
  24. Yee, Michelle Min Fang, et al. “Vitamin A and bone health: a review on current evidence.” Molecules 26.6 (2021): 1757.
  25. Van Ballegooijen, Adriana J., et al. “The synergistic interplay between vitamins D and K for bone and cardiovascular health: a narrative review.” International journal of endocrinology 2017 (2017).
  26. Martinaityte, Ieva, et al. “Vitamin D stored in fat tissue during a 5-year intervention affects serum 25-hydroxyvitamin D levels the following year.” The Journal of Clinical Endocrinology & Metabolism 102.10 (2017): 3731-3738.

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  1. susie welling

    January 22, 2022 , 9:23 am

    I’ve taken algecal for years. I am out of it and need it.
    I can’t seem to get that across.
    I have my own strontium and when it’s gone I’ll get yours.
    Please help me get algaecal.

  2. Kirby Johnson

    January 24, 2022 , 2:19 pm

    Hi Susie,

    You can place an order for AlgaeCal Plus HERE. If you prefer, you can also order over the phone with our Bone Health Consultants at 1-800-820-0184 (USA & Canada toll-free) 5am – 4pm PST weekdays, 6am – 4pm PST weekends ?

    – Kirby @ AlgaeCal

  3. Dolores McLenon

    January 22, 2022 , 4:22 pm

    I have been taking algaecal and strontium boost for one year. Recently I had a blood clot in my leg and my doctor put me on blood thinners. I read that strontium can cause blood clots and now I am afraid to take any more and quit. The blood clot dissolved from the blood thinner. It caused quite a bit of pain in my leg.

  4. Kirby Johnson

    January 25, 2022 , 11:46 am


    We’re so sorry to hear of the blood clot you’ve been dealing with. While Strontium Ranelate is associated with a small increased risk of blood clots, this hasn’t been found with strontium citrate, the form found in Strontium Boost. In fact, strontium citrate has been shown to be both safe and effective for bone health. We’d encourage you to discuss your blood clot in greater detail with your doctor to discover the root cause. Are you still currently taking your blood thinner? An important consideration while taking AlgaeCal with a blood thinner is to determine if there are any potential interactions with vitamin K2 (present in AlgaeCal Plus). You can call in for more information on both of these topics 😀 You can reach us at 1-800-820-0184 (USA & Canada toll-free) 5am – 4pm PST weekdays, 6am – 4pm PST weekends and you can always leave a voicemail if we’re out of the office!

    – Kirby @ AlgaeCal

  5. Margie Haines

    January 24, 2022 , 8:11 am

    A friend and I were just discussing this. If we need 800 IU of Vit. D and Algaecal provides 1600 IU, a vitamin might have 1000 IU, and we eat healthy with tuna and salmon, then is there a chance that these combined levels become toxic?

  6. Kirby Johnson

    January 25, 2022 , 10:00 am


    We’re glad to hear you’re discussing these questions with your friends! And it’s a great question! Vitamin D3 requirements tend to vary between individuals, but you’d likely benefit from additional vitamin D3 depending on your current vitamin D3 blood levels; it’s estimated that 42% of Americans are vitamin D3 deficient! You can learn more about testing and additional supplementation recommendations HERE. Vitamin D toxicity usually only occurs with extreme dosage (over 10,000 IU). Hope this helps!

    – Kirby @ AlgaeCal

  7. Beverly Northeast

    January 31, 2022 , 6:52 pm

    I need to order strontium citrate
    Please let me know the amount and if it will be delayed as I am completely out of it.
    Didn’t realize I was that low on it.
    Bev northeast

  8. Mary

    February 5, 2022 , 8:48 am

    What happens when you don’t take the doses of Algaecal for a week- my stomach gets toxic once or twice a year and I have to stop taking it. I do take it with food and feel I am not absorbing it.
    Is there anything I can do?

  9. Kirby Johnson

    February 7, 2022 , 10:33 am

    Hi Mary,

    While some people report improvements such as pain relief or feeling stronger, this is an individualized response and may not be the case for everyone. The best way to know you’re properly absorbing AlgaeCal is through the results of a DEXA scan. You can either reach out to us directly, or reference our instructional sheet HERE to verify you’re properly taking our supplements.

    Ceasing to provide your bones with the essential nutrients in AlgaeCal will serve to unbalance your bone-remodelling process and promote bone loss. We don’t anticipate ceasing to supplement with AlgaeCal for a week at a time to have any lasting negative impact on your bone health. We recommend discussing the symptoms of stomach toxicity you’re experiencing with your doctor to address the underlying cause, but it’s unlikely that the short discontinuations you’re engaging in will serve as a major setback in your bone health journey. Please don’t hesitate to call us at 1-800-820-0184 (USA & Canada toll-free) if you have any other questions or concerns.

    – Kirby @ AlgaeCal

  10. Linda Smith

    May 12, 2022 , 10:20 am

    The additional ways to ensure the amount of Vitamin D is essential to calcium absorption.

  11. Patricia Manson

    May 15, 2022 , 5:40 am

    Apparently, it’s a good idea to expose, different sites of skin, rather than just rolling up yr sleeves and baking the forearms, for better absorption and coverage!🌸

  12. Kirby Johnson

    May 18, 2022 , 1:55 pm


    ‘Tis the season! Enjoy all that beautiful sunshine this summer <3

    - Kirby @ AlgaeCal

  13. Sharon Van Boven

    May 15, 2022 , 3:16 pm

    As someone who suffers from severe vitamin D deficiency, this article was very helpful and much appreciated!!

  14. Susan Roth

    May 22, 2022 , 4:32 pm

    The importance of Vitamin D cannot be overstated. Found the food choices very helpful.

  15. Kirby Johnson

    May 26, 2022 , 3:39 pm


    We couldn’t agree more – thank you for taking the time to read through our article! If you’re interested in further reading on vitamin D3 and bone health, you might enjoy our article HERE <3

    - Kirby @ AlgaeCal

  16. Charlie Rogers

    May 26, 2022 , 8:07 am

    Very informative!

  17. Dianna henry

    June 9, 2022 , 7:19 am

    Thanks , I need to be more aware of when I am outside!

  18. Betty Skelding

    June 9, 2022 , 8:06 am

    Thanks Monica‼️ I take my AlgaeCal plus & Strontium Boost plus 2000 D-3 daily ,I am 73

  19. Kirby Johnson

    June 15, 2022 , 10:36 am


    Fantastic work! Keep on loving your bones and please don’t ever hesitate to let us know if we can be of any help along your bone-health journey <3

    - Kirby @ AlgaeCal

  20. Lois Ward

    January 28, 2023 , 7:04 am

    Great information! Thank you.
    Do you ever have sales on Algae products? I’m on a fixed income, so I have to watch it.
    I am 72 years old.

  21. Brianne AlgaeCal

    January 31, 2023 , 12:29 pm

    Hi Lois,

    Great question! While we do not have many sales, we do periodically have promotions. That said, while we unfortunately do not have any offers at the moment, we do always offer great savings in our bundles. We also recently launched our Subscribe and Save program to help you save on AlgaeCal monthly!

    The best way to stay up to date on any promotions would be to subscribe to our email newsletter. Please also feel free to give us a call at 1-800-820-0184 (toll free USA and Canada) any time, and any one of our Bone Health Consultants would be happy to go over our pricing options with you!

    – Brianne @ AlgaeCal

  22. Mahin

    January 28, 2023 , 12:24 pm

    Appreciated for this article, it was informative
    as usual.
    Warm Regards

  23. new yorkista

    January 28, 2023 , 7:59 pm

    The article clearly says 10-15 min of sunlight daily should be sufficient to produce normalized Vit D levels in the body, but later on states how difficult it is to get the HOURS of sunlight needed for sufficient Vit D production. Sloppy and just plain wrong. I’m disappointed that Algaecal would stop to irresponsible and inaccurate scaremongering. Tsk, tsk.

  24. Brianne AlgaeCal

    January 31, 2023 , 1:35 pm

    Hi there new yorkista,

    Thanks so much for commenting, and gosh we are so sorry for this confusion! It certainly was not our intent, and thanks so much for this feedback!

    For clarification, the 10-15 minutes of sunlight would be during the spring and summer months, when our skin is much for exposed to sunlight due to the warmer weather. You see the more skin is exposed to the sun, the better we can produce vitamin D.

    In the winter months however, depending on where you live of course, we are generally bundled up in our jackets, mitts and scarves, which doesn’t allow for much sun exposure on to the skin, because it is covered up. Therefore, we would have to spend MUCH more time in the sun to get the same effect!

    Ultimately, how much vitamin D supplementation you need (if any) would depend on your blood levels, and this is why we recommend testing this as the best way to know for sure if you are getting enough! 🙂

    I hope this helps!

    – Brianne @ AlgaeCal

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,