Vitamin D Deficiency Called Major Health Risk
The first clue came from rickets. Milk was fortified with vitamin D in the 1930s to eliminate the disorder, which can cause bowlegs and other bone malformations. But during the 1990s, doctors in several cities reported unusual numbers of cases, primarily in babies being breast-fed and mostly among African American children. Formula is fortified with vitamin D, but breast milk contains little, especially among women with dark skin.
In response, the American Academy of Pediatrics last spring instructed pediatricians to prescribe that all children, especially breast-fed babies, take vitamin D supplements through adolescence.
While it is clear that low vitamin D levels can lead to rickets in children, muscle problems in older people and probably brittle bones in the elderly, the link to other serious illnesses remains far more tentative. But many specialists say the case has steadily been getting stronger.
Vitamin D appears to interact with virtually every tissue in the body. Moreover, the incidence of certain diseases seems to vary depending on sun exposure and vitamin D levels.
For example, many cancers, most notably breast, colon and prostate cancer, seem to increase the farther you get from the equator, where exposure to ultraviolet light from the sun is greatest.
"The highest rate of prostate cancer is among African Americans, followed by countries in northern Europe. How are blacks like Scandinavians? They don't look alike, but in some important ways they have to be alike," said Gary G. Schwartz, a cancer researcher at Wake Forest University School of Medicine. "One way that they are alike is both groups have very low levels of vitamin D."
While there could be many other explanations, the idea that vitamin D may help prevent malignancies has been buttressed by animal and laboratory studies indicating it can act as a brake on cell growth, preventing the uncontrolled cell division that is cancer.
Similarly, vitamin D appears to damp down the immune system, and researchers have also found associations among sun exposure, vitamin D levels and the incidence of "autoimmune diseases" such as multiple sclerosis, lupus and diabetes, in which the immune system attacks the body.
Some studies suggest vitamin D can reduce blood pressure, which would cut the risk for heart disease and strokes -- the nation's leading causes of death. Others suggest that low vitamin D levels may contribute to depression and other psychiatric conditions.
"It's a major health problem," said Michael F. Holick, a Boston University scientist who is the most prominent proponent of the role of vitamin D in health. "Everybody has always associated vitamin D deficiency with rickets in children, and after childhood you don't have to worry. There's nothing further from the truth."
Holick and others argue that instead of the 200 to 600 international units a day that current recommendations suggest, most people should be getting at least 1,000 units a day. In a controversial new book, "The UV Advantage," Holick recommends exposing the hands, face, arms and legs to the sun for five to 15 minutes a day a few days a week, which he says would be enough to generate that amount without increasing the risk for skin cancer. Many people are not getting even that amount of sun exposure on a regular basis, Holick and others say.
"There's no question that chronic, excessive exposure to sunlight and sunburning incidents markedly increases your risk for skin cancer. But there's little evidence out there that if you practice safe sun exposure, it would increase your risk for skin cancer or wrinkling," Holick said.
But dermatologists and skin cancer experts argue that those recommendations are irresponsible and have little firm scientific support.
"Dr. Holick says vitamin D is a cure-all magic pill. If everyone took vitamin D, there would be no more cancer. But there's no evidence that is true," said James Spencer, vice chairman of dermatology at Mount Sinai School of Medicine in New York.
"Ultraviolet light contained in sunlight causes skin cancer and wrinkles. That's beyond dispute," Spencer said. "We already have an epidemic of skin cancer in this country."
Barbara Gilchrest, who chairs the dermatology department at the Boston University School of Medicine, said she asked Holick to resign his position in her department in February because of his views and because he receives some funding from the tanning-parlor industry. "He has, in my opinion, an enormous conflict of interest that he refuses to acknowledge," Gilchrest said.
Holick, who kept his other academic positions at the university, acknowledges he receives funding from the tanning industry, but he says it is a small portion of his budget and comes with no strings attached. "The dermatologists get a lot of money from the sunscreen industry and no one ever questions them about that," he said.
Many experts who believe vitamin D deficiencies play an important role in a range of diseases say people can get enough safely by taking vitamin D supplements, sidestepping the contentious sunlight debate.
"There's a lot of emotion in this fight, which is unfortunate," said Hector F. DeLuca, who studies vitamin D at the University of Wisconsin at Madison. "This is a very important issue. We really need to address two important questions: Are we getting enough vitamin D? I believe we are not. The other one is: What's the best way to get it? That's a matter of debate."
Others, meanwhile, say much more research is needed to figure out how much vitamin D people need and the best way to get it.
"We're a long way from making any definitive statement that Group X has a serious problem," NIH's Raiten said. "The evidence seems to imply that we need to look at it carefully, but I don't think we're in a position of being able to make any specific recommendations."
© 2004 The Washington Post Company