Guest Column: Why many may be deficient in vitamin D

By Dr. Jonathan Taylor

Northern Illinois Medical Group

Vitamin D is an essential nutrient for absorbing calcium and maintaining bone density. Many of the foods we buy today are fortified with vitamin D, and vitamin D is found in most of the multivitamins sold today.

Our bodies create vitamin D in our skin when we are exposed to sunlight. So why are so many people deficient in vitamin D?

Part of our deficiency is based on the season. Vitamin D is made in our skin when it is exposed to sunlight, or more specifically, to UV light above a UV index of 3. As the seasons progress toward winter, we cover up more and more of our skin, and the earth tilts away from the sun. This results in less exposure to the UV rays needed to produce sufficient vitamin D.

The average person living in the southern United States can get sufficient UV exposure by getting 10 to 15 minutes of direct sun exposure on their arms and faces a few times a week. The exposure needs to be direct (not through a window), and without the use of sunscreen lotion, which blocks the UV rays. Other factors affect the levels of UV light also, such as clouds or pollution.

Even with adequate UV light, older people, or people with darker skin, produce less vitamin D in their skin, so they will need even longer exposures. In the northern United States during the months from November to February, UV levels are not sufficient to produce vitamin D.

Another factor in vitamin D deficiency is diet. Vitamin D is not naturally abundant in our diet, other than in foods that are fortified with vitamin D. But the form of vitamin D usually used to fortify our foods and found in multivitamins is D2, made in plants and fungi, and usually extracted from yeast. The form of vitamin D created in our skin is D3, and some believe D2 is less effective than D3.

So, since we aren’t getting enough UV light, how much extra vitamin D should we take? The Institute of Medicine in 1997 recommended daily intake is 200 IU for adults up to 50 years, 400 IU from 51 to 70, and 600 IU for older than 70. This is not enough, however, to prevent chronic diseases or protect from osteoporosis. Recent studies indicate at least 1,000 IU daily is recommended for adults.

If you have any questions about the type of vitamin D you should take or how to tell if you are deficient, contact your health care provider to get more information.

Dr. Jonathan Taylor of Northern Illinois Medical Group, 5301 E. State St., Suite 101, Rockford, IL 61108, can be reached by phone at (815) 397-8500 or e-mail at, or visit

From the December 2-8, 2009 issue

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