Black Women May Need More Vitamin D in Winter

By Judy McBride
August 18, 1998

African-American women generally have stronger bones and a lower risk of fractures later in life than white women. But those living in northern latitudes may not have the strongest bones possible because of low vitamin D levels, a study suggests. The vitamin is essential for calcium absorption and is therefore integral to strong bones.

In the study, African-American women had about half as much 25-hydroxyvitamin D-- the most sensitive measure of D status--circulating in their blood throughout the year as white women. The African-Americans also had smaller increases in circulating vitamin D during the summer. Sunlight stimulates the skin to make the vitamin, but pigmented skin makes less.

Susan Harris and Bess Dawson-Hughes at the USDA Human Nutrition Research Center on Aging at Tufts, Boston, measured indicators of bone health in 90 healthy, young women--51 African-American and 39 white. All lived in the Boston area.

The African-American women got nearly as much vitamin D and calcium from food and supplements as the white women. So intake was not a major factor in the racial difference in vitamin D levels, the researchers reported in theJune issue of theAmerican Journal of Clinical Nutrition. They suggest that women of color might benefit from increasing their vitamin D intake, particularly during the short days of winter.

That's because parathyroid hormone rose only in the African-American women and only during the winter. The hormone signals low blood calcium and prompts the body to absorb more--which requires vitamin D. Apparently African-American women living in northern latitudes don't manufacture enough vitamin D during the summer to carry them through the winter months, the researchers concluded.

Scientific contact: Susan Harris or Bess Dawson-Hughes, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, 711 Washington St., Boston, Mass. 02111, phone (617) 556- 3073 (Hughes), (617) 556-3064 (Dawson-Hughes), fax (617) 556-3305, harris_si@hnrc.tufts.edu; hughesb@hnrc.tufts.edu .