Media General News Service
Published: May 17, 2010
Arthritis. Obesity. Diabetes. Heart disease. Depression. Cancer.
Vitamin D could help prevent all these and more, some experts say. And it's free. Most people can get it just by spending a little more time in the sun.
Known as the sunshine vitamin, it's long been known that vitamin D can help build strong bones and teeth. But in recent years, vitamin D deficiency has been linked to a growing number of health concerns.
"The benefits of vitamin D are varied and profound," says Michael F. Holick, a leading vitamin D expert and author of "The Vitamin D Solution: A 3-step Strategy to Cure Our Most Common Health Problems" (Hudson Street Press, $25.95).
"(Vitamin D) may be as vital to your heart and brain health as it is to bone health," Holick says. "Increasing levels of vitamin D can treat, prevent, and even reverse a remarkable number of daily ailments."
Holick cites a study that found women who took more than 400 IU (international units) of vitamin D reduced the risk of developing multiple sclerosis by 42 percent. A Canadian study found women with breast cancer were nearly twice as likely to see their cancer spread, and far more likely to die, if they were vitamin D deficient.
And a 2007 study in the American Journal of Clinical Nutrition concluded that post-menopausal women who improved their calcium and vitamin D levels substantially reduced all cancer risk.
"Vitamin D is the most common nutritional deficiency in the world, but its effects manifest in so many other conditions that people often focus on treating the symptoms instead of looking deeper in the cause," Holick says.
Most people don't get nearly enough D, which is produced through the skin by exposure to sunlight. With more people spending less time outdoors — and using sunscreen when they are outside — vitamin D deficiency is on the rise.
Three out of four Americans are deficient in vitamin D, up from one out of two 20 years ago, Holick says. About 40 percent to 60 percent of black adults are vitamin D deficient, he says.
In the black community, some experts are calling vitamin D deficiency a "hidden epidemic."
"Black women who develop breast cancer are more likely to die from the disease than white women," says Nagi B. Kumar, professor at the College of Medicine at the University of South Flor-ida and Moffitt Cancer Center. "Survival rates are also worse among blacks for colon, prostate and ovarian cancers. Why do blacks have a worse prognosis? One of the things could be their (vitamin D) blood levels are lower than others."
Kumar said several factors may explain why so many blacks are vitamin D deficient.
People get vitamin D primarily from the sun, through their diet and with over-the-counter sup-plements. The melanin in black skin acts as a natural sunscreen, which makes it difficult for the skin to make vitamin D. So the darker the skin, the less vitamin D you produce.
A black person requires three to five times more exposure to the sun to produce the same amount of vitamin D as a white person, Kumar says.
Blacks also have a higher incidence of lactose intolerance, so they don't use as much vitamin D fortified milk or other dairy products.
But with the risk of skin cancer, is it smart to get your D from more sun exposure?
Robert P. Heaney, professor of medicine at Creighton University Medical Center in Omaha, Neb., says no one knows for sure, but for those who aren't at an increased risk for skin cancer, about 15 minutes of unprotected sun exposure daily could help improve vitamin D deficiency.
"To put that into perspective, the human race didn't go away before the invention of sunscreen," Heaney says. Exposure to intense sunlight was mostly a year-round occurrence for our ancestors, he says.
Still, D isn't a cure for everything that ails the human race. "It's important. And our bodies need it to cope better," Heaney says. "But I don't want to promote it as a magic bullet."
On its website, the American Academy of Dermatology discourages people from getting vitamin D from sun exposure or indoor tanning because ultraviolet radiation can lead to skin cancer. The site suggests getting D from a healthy diet, which includes fortified foods, beverages and/or vita-min supplements.
Heaney recommends speaking to a physician to see whether it's necessary to take a supplement, and if it is, to determine the appropriate dose.
The only way to know whether you're vitamin D sufficient is by having a 25-hydroxyvitamin D test, also called a 25 (OH) D test.
Most people have never been tested and don't know they have a deficiency, Kumar says. But that's changing as more doctors jump on the vitamin D bandwagon.
Patients who suffer from aches and pains, which can be signs of Vitamin D deficiency, often feel better a few weeks after boosting their intake, Kumar says.
"It's very easy to raise low levels of vitamin D," he says. "If you have a deficiency, you can start to feel better in a matter of weeks."
（摘自Vitamin D Today）