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 Agingat 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
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, email@example.com;
Story contacts Human Nutrition Research Center on Aging