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 UC Davis.

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 UC Davis 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.