by Kevin S. Liu, M.D.

Question
On the matter of sun exposure as an important source of vitamin D, what level of light intensity is most desirable? And what’s the most sensible approach to getting sun?

Answer
This topic has received quite a bit of coverage in the last several years, as experts have tried to decide just what to recommend. It is true that sunlight exposure provides a good source of vitamin D. However, it’s important to understand a few points about that very issue.

HOW VITAMIN D WORKS WITH THE SKIN
The skin contains a chemical that changes into an inactive form of vitamin D upon exposure to ultraviolet radiation, type B. The liver and kidneys then convert it into an active form.

As you might imagine, dermatologists don’t like this whole idea since sunlight exposure also increases your risk for skin cancer and causes your skin to age more quickly. And anyway, that brief amount of sun still isn’t enough to produce ample vitamin D on cloudy or smoggy days. (Window glass also blocks UVB rays.)

However, other experts are concerned that food alone doesn’t yield enough vitamin D to keep you from being deficient.

As a compromise, many currently recommend exposing your hands, face and arms to direct sunlight for about 10 to 15 minutes a day, three times a week, using no sunscreen. In addition to that, get more vitamin D through supplements and/or foods, such as vitamin-D-fortified orange juice and milk.

KEVIN S. LIU, M.D., is a member of our print magazine editorial board and a board-certified family doctor in Keller, Texas.

Last updated and/or approved: August 2009. Bio current as of summer 2007.
Original article appeared in summer 2007 issue.

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