The disparity in rates of heart disease deaths between blacks and whites can be attributed in large part to low levels of vitamin D in a substantial portion of the black population, researchers have found. Their dark skin cuts down on the production of vitamin D--which is produced primarily by sunlight--particularly among those who live at higher latitudes where sunlight is less intense than it is closer to the equator, said Dr. Kevin Fiscella of the University of Rochester, a co-author of the paper appearing Thursday in the Annals of Family Medicine. In general, blacks require three to five times as much exposure to sunlight as whites to produce the same amount of vitamin D.
The study also found a higher risk of death from heart disease in whites with abnormally low levels of vitamin D.
Low levels of vitamin D have previously been linked to increases in high blood pressure, obesity, diabetes, peripheral artery disease, kidney disease and breast cancer. To further explore the links, Fiscella and Dr. Peter Franks of UC Davis studied vitamin D levels in 15,000 people who participated in the third National Health and Nutrition Survey from 1988 to 1994 and correlated them to deaths reported in the National Death Index through 2001. Overall, they found that the 25% of subjects in the study with the lowest blood levels of vitamin D had a 40% higher risk of dying from heart disease than those in the upper 75%. Blacks in the study had a 38% higher risk of dying from heart disease than whites, they found, but low blood levels of vitamin D accounted for about two-thirds of the increased risk. The rest could be attributed to poverty.
Current federal guidelines for vitamin D call for consumption of 400 International Units (IUs) of vitamin D for most adults and 600 IUs for those over age 70. Fiscella did not make a recommendation for daily intake, but most researchers studying vitamin D now take between 1,500 and 2,000 IUs per day. The general consensus is that no harm is associated with a daily intake of up to 10,000 IUs. And many physicians agree that, when you have your annual visit with your doctor, he or she should measure your vitamin D levels.
-- Thomas H. Maugh II
Twenty minutes of sunlight per day provides most whites with enough vitamin D, but blacks require three to five times as much exposure. Credit: Al Schaben / L.A. Times