If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Vitamin D, also known as “the sunshine vitamin,” is pretty unique. While we can get it from the food we eat, our body can make it with a little help from the sun.
Vitamin D is produced when the skin is exposed to sunlight, creating a substance that the liver and kidneys convert to forms several body systems can use. Vitamin D is present in a variety of foods, but for many of us, the main source of it is sunlight (Nair, 2012).
But in the winter months, when we spend less time outside and get less sun exposure, as well as in certain areas of the globe where the sun isn’t as strong, it can be difficult (if not impossible) to get enough sunlight to produce adequate vitamin D. Experts estimate that 40% of Americans and as many as 1 billion people worldwide may be deficient in vitamin D (Parva, 2018).
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Vitamin D’s role in the body
Vitamin D plays a crucial role in our health. While the most well-recognized role of vitamin D might be its involvement in calcium absorption and bone mineralization, it is also involved in a range of other processes.
Evidence has shown that, in addition to preventing osteoporosis and fractures, it helps with regular immune system function, participates in the body’s defenses against cancer, helps the pancreas regulate blood sugar, and even seems to be involved in reducing the risk of cardiovascular disease.
Vitamin D dosage
The National Institutes of Health recommends a daily intake of vitamin D of 600 IU (15 mcg) for adults up to age 69 and 800 IU (20 mcg) for adults 70 and older to maintain normal vitamin D levels.
Your healthcare provider can perform a simple blood test to determine if you’re getting enough vitamin D. If your healthcare provider determines that you have a vitamin D deficiency, they will likely instruct you to increase your intake beyond that level to replenish your stores.
Good food sources of vitamin D include fatty fish like salmon and tuna, fish oil, vitamin D-fortified milk, eggs, and fortified breakfast cereals. Here are some examples (NIH, n.d.):
- Cod liver oil: 1 tbsp contains 1,360 IU (34 mcg)
- Salmon: a 3 oz. serving contains 570 IU (14.2 mcg)
- Vitamin D-fortified 2% milk: 1 cup contains 120 IU (2.9 mcg)
- Fortified cereal: 1 serving contains 80 IU (2.0 mcg)
- One large egg: 44 IU (1.1 mcg)
If you have trouble getting enough vitamin D from your diet, your healthcare provider may recommend adding a dietary supplement that contains vitamin D to your daily routine.
While maintaining adequate levels of vitamin D is crucial for many of our bodies’ systems, too much vitamin D can actually be detrimental to your health. Because vitamin D regulates the body’s calcium absorption, excessive levels can result in hypercalcemia (high calcium in the blood), which can result in a range of potentially dangerous complications.
If your doctor tells you to add a supplement to your diet to maintain or increase your vitamin D levels, make sure to read the label carefully to ensure that it contains an appropriate recommended dietary allowance (RDA) for your age.
Unlike other vitamins which we have to get from our food, our body is actually capable of producing a precursor to vitamin D. When we get sun exposure, UVA light converts that precursor to vitamin D.
So while, theoretically, it is possible to get your daily recommended dose from the sun, there are a few caveats. Most people don’t actually spend enough time in the sun to get all the vitamin D they need. Also, we’re all familiar by now with the risks of excessive sun exposure, such as premature aging and even skin cancer.
So while some researchers believe that getting five to 30 minutes of sun exposure to your face, arms, legs, or back (without sunscreen, between 10 a.m. and 3 p.m., at least twice a week) can produce a sufficient amount of vitamin D, choosing foods rich in vitamin D or adding an appropriate supplement to your diet is often a safer option (Holick, 2007).
- Aloia, J. F., Patel, M., Dimaano, R., Li-Ng, M., Talwar, S. A., Mikhail, M., Pollack, S., & Yeh, J. K. (2008). Vitamin D intake to attain a desired serum 25-hydroxyvitamin D concentration. The American Journal of Clinical Nutrition, 87(6), 1952–1958. https://doi.org/10.1093/ajcn/87.6.1952. Retrieved from https://academic.oup.com/ajcn/article/87/6/1952/4633503
- Aranow, C. (2011). Vitamin D and the immune system. Journal of Investigative Medicine : the Official Publication of the American Federation for Clinical Research, 59(6), 881–886. https://doi.org/10.2310/JIM.0b013e31821b8755. Retrieved from https://jim.bmj.com/content/59/6/881
- Bischoff-Ferrari, H. A., Willett, W. C., Wong, J. B., Giovannucci, E., Dietrich, T., & Dawson-Hughes, B. (2005). Fracture Prevention With Vitamin D Supplementation: A Meta-analysis of Randomized Controlled Trials. JAMA. 293(18):2257–2264. doi:10.1001/jama.293.18.2257. Retrieved from https://jamanetwork.com/journals/jama/article-abstract/200871
- Holick, M. F. & Chen, T. C. (2008). Vitamin D deficiency: a worldwide problem with health consequences. The American Journal of Clinical Nutrition, 87(4), 1080S–6S. https://doi.org/10.1093/ajcn/87.4.1080S. Retrieved from https://academic.oup.com/ajcn/article/87/4/1080S/4633477
- Meeker, S., Seamons, A., Maggio-Price, L., & Paik, J. (2016). Protective links between vitamin D, inflammatory bowel disease and colon cancer. World Journal of Gastroenterology, 22(3), 933–948. https://doi.org/10.3748/wjg.v22.i3.933. Retrieved from https://www.wjgnet.com/1007-9327/full/v22/i3/933.htm
- Nair, R. & Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin. Journal of Pharmacology & Pharmacotherapeutics, 3(2), 118–126. https://doi.org/10.4103/0976-500X.95506. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/
- National Institutes of Health, Office of Dietary Supplements – Vitamin D. (n.d.). Retrieved July 17, 2020 from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- Parva, N. R., Tadepalli, S., Singh, P., Qian, A., Joshi, R., Kandala, H., Nookala, V. K., & Cheriyath, P. (2018). Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012). Cureus, 10(6), e2741. https://doi.org/10.7759/cureus.2741. Retrieved from https://www.cureus.com/articles/11792-prevalence-of-vitamin-d-deficiency-and-associated-risk-factors-in-the-us-population-2011-2012
- Schwalfenberg, G. (2008). Vitamin D and diabetes: improvement of glycemic control with vitamin D3 repletion. Canadian Family Physician Medecin de Famille Canadien, 54(6), 864–866. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2426990/
- Vacek, J. L., Vanga, S. R., Good, M., Lai, S. M., Lakkireddy, D., & Howard, P. A. (2012). Vitamin D Deficiency and Supplementation and Relation to Cardiovascular Health. The American Journal of Cardiology, 109(3), 359–363. https://doi.org/10.1016/j.amjcard.2011.09.020. Retrieved from https://www.ajconline.org/article/S0002-9149(11)02933-X/fulltext
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.