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Studying the relationship between vitamin D deficiency and disease in vulnerable populations is the aim of a new $600,000 grant from the National Institutes of Health to the Center of Excellence for Nutritional Genomics.

"Vitamin D deficiency is one of the most serious public health issues facing the U.S. today," said Ray Rodriguez, director of the center and professor of molecular and cell biology at ΢²ªÊÓƵ.

Vitamin D has long been known to affect bone growth, and deficiency leads to rickets or deformed limbs. But recent research shows that vitamin D has wide-ranging effects, from fetal development to neurodegenerative disease in the elderly, Rodriguez said.

Lead investigator Charles Stephensen, a researcher with the U.S. Department of Agriculture's Western Human Nutrition Research Center (WHNRC) at Davis and an adjunct professor in the ΢²ªÊÓƵ Department of Nutrition, is currently assessing how sunlight, diet and skin pigment contribute to vitamin D status. Stephensen's team is planning to study whether vitamin D supplements strengthen the immune system in subjects at high risk of deficiency.

Humans get most of their vitamin D through the action of sunlight on skin. People of color and those living in high latitudes are particularly vulnerable to vitamin D deficiency. Concerns about skin cancer may be causing some light-skinned people to reduce their exposure to sunlight and put themselves at risk of deficiency.

Many nutrition researchers are concerned that the current recommendation of 400 international units of vitamin D per day is too low to be effective in reducing the risk of chronic diseases, neurological diseases and cancer.

In a review published in the FASEB Journal in December 2007, Bruce Ames and Joyce McCann at the Children's Hospital Oakland Research Institute, which is a partner in the Center of Excellence for Nutritional Genomics, wrote that there is ample evidence to suggest an important role for vitamin D in brain development and function, and that supplementation for groups chronically low in vitamin D is warranted.

"It may turn out that vitamin D is the single most important supplement one can take to improve health and reduce disease risk," Rodriguez said.