Vitamin D is a fat-soluble vitamin. It helps the body absorb calcium and plays a crucial role in the growth and maintenance of strong, healthy bones. In children, adequate vitamin D is important for the prevention of rickets. And in adults, vitamin D deficiency has been associated with a greater incidence of hip fracture. Increased intakes of vitamin D, on the other hand, have been associated with less bone loss in older women. This has led some researchers to believe that vitamin D supplementation may help prevent fractures resulting from osteoporosis.
Vitamin D may also play a role in a number of other conditions as well. For example, vitamin D deficiency has been related to muscle weakness and pain. In one study, patients with low back pain received high doses of vitamin D for 3 months, which resulted in significant improvement of their symptoms.
Also, there is some research to suggest that this supplement may play a role in cancer prevention. Vitamin D receptors have been found in breast and prostate tissue, implying that such a link does exist. Additionally, there is some evidence hinting that low levels may play a role in the development of high blood pressure. There is also preliminary research suggesting that long-term vitamin D supplementation decreases the risk of multiple sclerosis.
People who are at a high risk for vitamin D deficiencies are the elderly, those who get minimal sun exposure, those with darker skin, or those who use sunscreen whenever outside. Also, people with conditions that may impact intestinal absorption, such as Crohn's disease, are at risk.
In addition, infants that are breastfed require additional supplementation with vitamin D starting within the first days of life. Requirements for pregnant women are the same as for healthy adults. Some believe that pregnant mothers should take more vitamin D than recommended. However, since there is an increased risk of vitamin D toxicity with increased intake, such recommendations need to be discussed individually with a doctor.
The recommended intakes for vitamin D are:
|Age (years)||Recommended Dietary Allowance
|0-12 months||400 (adequate intake)|
|71 years and older||800|
|Pregnant and breastfeeding women||600|
Vitamin D is found in some foods, but the main sources are fortified milk and sunlight. The ultraviolet rays of the sun react with cholesterol present on the skin and create previtamin D3. This compound goes through a series of reactions involving the kidneys and the liver, and the final product is vitamin D.
Most people's bodies can make enough vitamin D with 5-30 minutes of sun exposure twice weekly. However, this synthesis is affected by age, season, latitude, time of day, cloud cover, smog, and skin pigmentation.
Other food sources of vitamin D include:
Vitamin D content
|Cod liver oil||1 tablespoon||1,360|
|Salmon, cooked||3 ounces||447|
|Tuna fish, canned in water||3 ounces||154|
|Sardines, canned in oil||2 sardines||46|
|Milk, vitamin D fortified||1 cup||115-124|
|Margarine, fortified||1 tablespoon||60|
|Liver, beef, cooked||3 ounces||42|
|Egg (vitamin D is in the yolk)||1 large||41|
Eat Right—Academy of Nutrition and Dietetics
International Food Information Council
Dietitians of Canada
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Sunscreen FAQs. American Academy of Dermatology website. Available at: https://www.aad.org/media/stats/prevention-and-care/sunscreen-faqs. Accessed March 10, 2017.
Vitamin D. Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional. Updated February 11, 2016. Accessed March 10, 2017.
Vitamin D. Oregon State University Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/mic/vitamins/vitamin-D. Updated November 2014. Accessed March 10, 2017.
Vitamin D deficiency in adults. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T113821/Vitamin-D-deficiency-in-adults. Updated October 5, 2015. Accessed March 10, 2017.
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Last reviewed March 2017 by Michael Woods, MD, FAAP Last Updated: 3/10/2017