DAVIS, CALIF. — People of African ancestry with low sun exposure need 2,100 to 3,100 International Units (I.U.) of vitamin D daily, more than three times the currently recommended A.I. levels of 200 I.U. for people age 0-50, 400 I.U. for people age 51-70 and 600 I.U. for people over age 70, according to a study that appeared on-line Jan. 6 in The Journal of Nutrition. During the winter, people of European ancestry with high sun exposure need 1,300 I.U. of vitamin D daily, according to the study.

Researchers from the University of California, Davis, the U.S. Department of Agriculture’s Western Human Nutrition Research Center in Davis, Colorado State University in Fort Collins, and Queensland University of Technology in Queensland, Australia, studied 72 people for seven to eight weeks in the fall, winter, spring and summer in Davis. They sought to model the effects of sun exposure, vitamin D intake and skin reflectance (pigmentation) on serum 25-hydroxyvitamin D (25[OH]D) in young adults with a wide range of skin reflectance and sun exposure.

The Food and Nutrition Board of the Institute of Medicine, which is part of the National Academy of Sciences, in 1997 set adequate intake (A.I.) levels of vitamin D ranging from 200 I.U. to 600 I.U., depending on age. The Institute of Medicine has formed a committee to review dietary reference intakes for vitamin D and calcium and may set new levels later this year.