Vitamin d deficiency

Many Americans, particularly African Americans, may be suffering from unrecognized deficiencies of a key nutrient -- vitamin D -- that increase the risk of bone problems and perhaps a host of other diseases, a growing number of scientists say.
Pediatricians scattered around the country have been surprised to see children suffering from rickets, a bone disorder caused by vitamin D deficiency that had been largely relegated to a bygone era. In response, many scientists have begun pushing to sharply boost the official recommendations for how much vitamin D everyone should get daily, either by taking supplements, by eating more food that contains the nutrient or from the sun -- a major source of vitamin D.
Suggestions that people get more sun exposure, however, have sparked an unusually intense, and sometimes bitter, debate. Skin cancer experts are alarmed that people will disregard warnings about unprotected sun exposure, making them more vulnerable to what is the most common malignancy.
The debate is complicated by the many uncertainties about vitamin D. Skin produces vitamin D when hit by ultraviolet light in sunlight. The amount depends on where people live, skin pigment, age and other factors. With people spending more time indoors, covering up and slathering on sunblock when they are outside, and smog obscuring the sun on many days, the amount of vitamin D people create naturally is probably very low, many scientists say.
"All along the northern United States, where we have long winters, a lot of snow, not much sunshine all winter, there is endemic vitamin D deficiency," said Paresh Dandona of the State University of New York at Buffalo, who treated six patients disabled by misdiagnosed vitamin D deficiencies.
A number of studies have found what could be disturbingly low levels of vitamin D in many populations, including children, the elderly and women. One federal study of women nationwide found that perhaps nearly half of African American women of childbearing age may be vitamin D deficient.
Milk was fortified with vitamin D in the 1930s to eliminate the disorder, which can cause bowlegs and other bone malformations. 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. 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.
"The highest rate of prostate cancer is among African Americans, followed by countries in northern Europe. "One way that they are alike is both groups have very low levels of vitamin D."
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. 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. "We already have an epidemic of skin cancer in this country."
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. We really need to address two important questions: Are we getting enough vitamin D?