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Friday, January 30, 2015
Vitamin D is a fat-soluble vitamin that is found naturally in only a few foods, including fatty fish such as salmon, sardines, and tuna canned in oil. Some foods, including milk and many breakfast cereals, are fortified with vitamin D, which helps the body absorb calcium.
The body can also make its own vitamin D when the skin is exposed to sunlight. Studies suggest that 5 to 30 minutes of sun exposure, between 10 a.m. and 3 p.m. at least twice a week, to the face, arms, legs, or back without sunscreen usually offers enough sunlight to give you sufficient vitamin D stores (Office of Dietary Supplements with the National Institutes of Health).
However, the Skin Cancer Foundation takes issue with that kind of recommendation. The organization cites research indicating that even a small amount of unprotected exposure to the sun's ultraviolet rays "contributes to cumulative skin damage, accelerating aging, and increasing our lifetime risk of skin cancer."
For vitamin D, the recommended amount to get each day increases with age:
Why? Well, the older you are, the more trouble your body has synthesizing vitamin D from exposure to sunlight. This makes older adults at risk for vitamin D deficiency. Other at-risk groups include anyone with limited sun exposure; people with dark skin (the melanin in darker skin reduces the ability to produce vitamin D from sunlight); and people who are obese (fat cells hold onto vitamin D, reducing the amount in the body's circulation system).
If you are not getting enough vitamin D through your dietary intake, should you expose your skin to the sun without sunscreen for extra vitamin D? Experts offer conflicting guidance on the topic, depending on which they believe carries more risk: a vitamin D deficiency or the potential to develop skin cancer.
First, try tracking your intake of vitamin D for a few days. The Daily Value for vitamin D on nutrition facts labels is 10 micrograms or 400 IUs -- the recommended amount for people 50 or younger. The amount is listed as a percentage. If you are 50 or younger and are eating a food with 25 percent of vitamin D, just add up the percentages until you reach 100 percent. Keep counting to 200 percent if you are between 51 and 70, or to 300 percent if you are 71 or older. Be sure to include the percent of vitamin D in a multivitamin if you take one.
If you find you are not consuming enough vitamin D, ask your doctor about additional supplementation or about the relative risks you might face with additional sun exposure.
This article originally appeared in Chow Line (04/25/08), a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center and was adapted for use on NetWellness with permission, 2007.
Last Reviewed: Apr 29, 2008
Lydia Medeiros, PhD
College of Education and Human Ecology
The Ohio State University