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Here's Why: | Here's How:

Here's Why:

Vitamin D imageVitamin 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.

Recent research suggests that vitamin D may play a role in a number of other conditions, as well. More research is needed to confirm the findings, though. 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 three 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 may 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)
1-70 years600
71 years and older800
Pregnant and breastfeeding women600

Here's How:

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 10-15 minutes of sun exposure 2-3 times per week. 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:

FoodServing size Vitamin D content
Cod liver oil1 tablespoon1,360
Salmon, cooked3 ounces447
Mackerel, canned3 ounces213
Sardines, canned in oil2 sardines46
Milk, vitamin D fortified1 cup98
Margarine, fortified1 tablespoon60
Liver, beef, cooked3 ounces42
Egg1 large41
  • Eat fish, especially fatty fish such as salmon and mackerel, 2 times per week.
  • Drink vitamin D-fortified milk.
  • Get sun exposure, but be careful to watch for sunburn. Sunlight is a major cause of skin cancer. Fifteen summer minutes of sun exposure to face and arms will allow most persons to synthesize adequate vitamin D and minimize the risk of skin damage. If you will be out in the sun for more than a few minutes, it is important to protect against skin cancer by wearing protective clothing or putting on sunscreen with an SPF (sun protection factor) of 15 or more. In most northern climates, winter sun is too obstructed and low in the sky to allow vitamin D synthesis in the skin. In the winter, vitamin D supplements or multiple servings of milk and fatty fish may be necessary for good health.

Academy of Nutrition and Dietetics


International Food Information Council



Canada's Food Guide


Dietitians of Canada



Breastfeeding. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated March 19, 2013. Accessed April 3, 2013.

Giovannoni G, Ebers G. Multiple sclerosis: the environment and causation. Curr Opin Neurol. 2007;20:261-268.

Ginde AA, Mansbach JM, Camargo CA. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009;169:384-390.

Heath KM, Elovic EP. Vitamin D deficiency: implications in the rehabilitation setting. Am J Phys Med Rehabil. 2006;85:916-923.

Michels KB, Mohllajee AP, Roset-Bahmanyar E, Beehler GP, Moysich KB. Diet and breast cancer: a review of the prospective observational studies. Cancer. 2007;109(Suppl 12):2712-2749.

Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA. 2006;296:2832-2838.

Vitamin D. Office of Dietary Supplements website.Available at: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional. Updated June 24, 2012. Accessed April 3, 2013..

Vitamin D. Oregon State University Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/index.html. Updated June 22, 2011. Accessed April 3, 2013.

Wagner CL, Greer FR. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics. 2008;1221142-1152.

Last reviewed April 2013 by Brian Randall, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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