The influx of research indicating that vitamin D may have a wide array of health benefits has intensified the debate over whether federal guidelines for the sunshine vitamin are outdated—leaving millions vulnerable to cancer, heart disease, diabetes and other ailments.
The studies have produced evidence that low levels of vitamin D make:
- Men more likely to have heart attacks.
- Breast and colon cancer victims less likely to survive.
- Kidney disease victims more likely to die.
- Children more likely to develop diabetes.
Two other studies suggested that higher vitamin D levels reduce the risk of dying prematurely from any cause.
In response to these studies and earlier findings, several medical societies are considering new recommendations for a minimum daily vitamin D intake. In addition, the American Medical Association recently called for the government to update its guidelines and federal officials are planning to launch that effort.
Other leading experts caution that it is premature for people to start taking large doses of vitamin D. While the new research is provocative, experts argue that the benefits remain far from proven. Vitamin D can be toxic at high doses, and some studies suggest it could increase the risk for some health problems, experts say.
"The data is intriguing and serve as, no pun intended, food for further fruitful research," says Mary Frances Picciano, at the Office of Dietary Supplements of the National Institutes of Health. "But beyond that, the data is just not solid enough to make any new recommendations. We have to be cautious."
On the other hand, Reinhold Vieth, a professor of nutritional sciences and pathobiology at the University of Toronto, is part of a small but vocal group of researchers pushing doctors and patients to stop waiting for new official guidelines. This group suggests that physicians routinely test their patients for vitamin D deficiencies, and that more people—especially African Americans—should take supplements and increase their exposure to the sun.
"The bottom line is we now recognize that vitamin D is important to the health of children and adults, and may help prevent many serious chronic diseases," says Michael Holick, a professor of medicine, physiology and biophysics at Boston University.
Scientists have long known that vitamin D is a vital nutrient the skin produces when exposed to ultraviolet light from sunlight and other sources. The amount of vitamin D produced varies depending on where the person lives, skin pigment, age and other factors. African Americans and other dark-skinned people, as well as anyone living in northern latitudes, produce far less vitamin D than other groups. Overall, as people spend more time indoors on the computer, watching television, working at desk jobs, and covering up and using sunscreen when they do venture outdoors, the amount of vitamin D that people create in their bodies has been falling.
Studies have found that deficiencies may be common, with perhaps half of adults and children having what some consider inadequate levels. Federal guidelines call for people to get 200 to 600 international units (IUs) a day, depending on age and other factors. But those recommendations were last updated in 1997 and were aimed primarily at preventing bone diseases, such as rickets in children and osteoporosis in the elderly. The Canadian Cancer Society recently upped its recommendation to 1,000 IUs a day, and some believe Americans should routinely consume at least 2,000 IUs a day.
Source: San Francisco Chronicle