News & tips on health, fitness and nutrition

Saturday, May 17, 2008

Vitamin D : Many Americans don't get enough of a crucial vitamin

Dr. Michael Holick is one of the foremost authorities on vitamin D. And he's also the man behind a 2007 New England Journal of Medicine article that declared: "It has been estimated that 1 billion people worldwide have vitamin D deficiency or insufficiency."

On Holick's Web site, he notes that vitamin D is "made in the skin as a result of exposure to sunlight." And it's "not a vitamin, but a hormone."

Beyond sun rays, the National Institutes of Health notes that vitamin D is present in, among other things, fatty fish and beef liver. And it's added to items such as fortified milk, juice, yogurt, margarine and ready-to-eat cereal. It also comes in supplement form.

Local nutritionist Cece Davis discovered just how important it is to prevent vitamin D deficiency or insufficiency at a recent nutritionists' conference in Boston, where Holick asked his large audience for a show of hands.

Holick wanted to know how many people in the audience had checked their vitamin D status. Once prompted, about 30 to 40 percent of the audience members raised their hands, Davis recalled. Then Holick asked, "OK, of those people, how many of you were deficient?"

They all raised their hands.

Davis was stunned. After all, these were fellow health experts and, still, they were deficient.

"I was flat amazed at several things," Davis recalled of Holick's speech. "One, how much of a problem it really is and how it is linked to many diseases."

In Holick's journal article, he wrote that vitamin D plays a role in "decreasing the risk of many chronic illnesses, including common cancers, autoimmune diseases, infectious diseases and cardiovascular disease."

Among the causes of vitamin D deficiency Holick cites in his article are inadequate sun exposure; insufficient skin pigment to absorb UVB rays; aging; living above 35 degrees north latitude; obesity and "breast-feeding without vitamin D supplementation."

To prevent vitamin D deficiency, nutrition consultant Nancy Bacon, of the Oklahoma State Department of Health, recommended taking a multivitamin that includes vitamin D, eating vitamin D-rich foods and getting 10 to 15 minutes of sunlight on one's face and arms without sunscreen twice a week. "

However, if you have a family history (of skin cancer) or you are concerned about it, I would not go that route," she said. "I would definitely talk to your physician for specific recommendations."

When it comes to figuring out if a person is vitamin D deficient, Davis said, "The best thing to do is go to the doctor and have a blood test run. ... An alternate method is to assume most of us are deficient and to go ahead and purchase a vitamin D supplement."

Holick wrote, "providing children and adults with approximately at least 800 (international units) of vitamin D3 per day, or its equivalent, should guarantee vitamin D sufficiency unless there are mitigating circumstances."

Later, Holick wrote, "Unless a person eats oily fish frequently, it is very difficult to obtain that much vitamin D3 on a daily basis from dietary sources ... Thus, sensible sun exposure (or ultraviolet B irradiation) and the use of supplements are needed to fulfill the body's vitamin D requirement."

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