If you've been to this blog before, then you probably know I'm pretty emphatic when it comes to the importance of staying out of the sun and vigilantly applying sunscreen. But the sun does offer one important benefit: UV exposure stimulates the body to produce vitamin D.

Recent studies have revealed, though, that many people may be vitamin D deficient and not even know it - even people in their 20s. But don't be too quick to blame sunscreen! A recent study performed in sunny Hawaii found that vitamin D deficiency was common even in people who didn't wear any sunscreen.

Doctors are increasingly concerned about vitamin-D deficiency, as research shows that low levels of this crucial vitamin put us at a greater risk for osteoporosis, since vitamin D is essential for proper calcium absorption, as well as many types of cancer.

For this reason, the medical community has become increasingly aware of the importance of using basic blood tests to determine vitamin D levels - and it's really never too early start thinking about this issue. I'm going to start performing this quick and easy test in my own clinic, and I urge you to talk to your doctor about having your own vitamin D levels tested.

But if you do find out that you're vitamin-D deficient, don't take that as a license to bask in the sun! Why exchange one health risk for another? It is much safer in the long run to rethink your diet and include plenty of vitamin D: milk is typically vitamin-D fortified, for example, and eggs, fatty fish (like salmon and cod, or cod liver oil), and mushrooms are also great sources.

In many cases, though, dietary changes aren't enough, but vitamin D supplements are another effective option, readily available at any drugstore. That's another good reason to get your blood drawn - it's important to assess how much supplementation you need. Those at risk for vitamin D deficiency, for example, may need up to 1000 IU a day of vitamin D, while 400 IU a day is generally sufficient otherwise.

Wishing you great skin!

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Dr. Baumann is author of the best-selling book, "The Skin Type Solution." To learn more about her revolutionary skin typing system, visit her Web site, SkinTypeSolutions.com. 

All of Dr. Baumann's recommended skin care products are available online, and a portion of proceeds goes to The Dermatology Foundation.

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