Evening Edge

A few weeks ago I was attending the annual symposium of the Sports, Cardiovascular and Wellness Nutritionists conference in Boston and I was questioning my sanity at a very early Saturday morning lecture. But when I saw the white-haired speaker, with his first slide showing a sunrise and blasting the theme music from "2001: A Space Odyssey," I knew it would be an entertaining lecture.

Dr. Michael Holick, professor of medicine at Boston University, is on a quest to educate the world about the benefits of the sunshine vitamin -- vitamin D. Although Holick has become a controversial figure in recent years in part because of funding he’s received from the indoor tanning industry, his work is also supported by the National Institutes of Health, and his research has appeared in top-tier medical journals.

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Foods are a poor source of vitamin D, but exposure to small amounts of sunlight (5 to 15 minutes) twice a week is enough for most people to make vitamin D.

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Here are his main points:

• Vitamin D is crucial for bone health because it allows our bodies to absorb calcium.

• The sun has been demonized and so we cover bodies from head to toe with sunblock, which blocks harmful UV rays but also blocks the ability to make adequate vitamin D.

• Foods are a poor source of vitamin D, but exposure to small amounts of sunlight (5 to 15 minutes) twice a week is enough for most people to make vitamin D.

• Vitamin D deficiency is more common than previously thought and some groups are at higher risk. Thirty percent to 50 percent of African-Americans are estimated to have low levels of vitamin D because their skin pigment blocks vitamin D production. Obese people tend to sequester vitamin D in their fat so blood levels can be low.

• Most of us need 1,000 IU of vitamin D a day; both vitamin D2 (ergocalciferol, which is added to milk) and vitamin D3 (cholecalciferol, which is found in some supplements) can maintain healthy blood levels.

• Although vitamin D can be toxic when taken in too large a dose from supplements, natural exposure from the sun doesn't cause the same harm.

• If taking supplements, limit to no more than 2,000 IU per day, unless prescribed larger doses by a doctor.

• To find out if you are "D-eficient," ask your doctor to measure your blood level of 25(OH)D.

For more information on vitamin D, visit Holick's Web site at www.vitamindhealth.org. You can watch his entertaining lecture by clicking on the link to ECTS Presentation. So, on these beautiful spring days, take a walk and expose your arms and legs to sunlight for a few minutes before you slather on the sunblock.

Chris Rosenbloom, Ph.D., R.D., is a professor of nutrition in the College of Health and Human Sciences at Georgia State University. She'll answer nutrition questions of general interest. Send your questions to her c/o The Atlanta Journal-Constitution, Sixth Floor, 72 Marietta St. N.W., Atlanta, GA 30303. Or e-mail her at dietitian@ajc.com.