Jan. 7, 2010 -- African-Americans are more likely than whites to die of heart attacks, strokes, and other cardiovascular causes. Now intriguing new research suggests that low vitamin D levels may help explain this disparity.
In an effort to examine the role of vitamin D in the racial disparity in cardiovascular death, researchers analyzed data from a national health and nutrition survey that included more than 15,000 people.
Vitamin D levels were measured at the time the survey was conducted, and the participants were followed for up to 12 years.
Blacks were 38% more likely to die of cardiovascular causes than non-Hispanic whites, and the researchers concluded that most of this excess was related to their lower vitamin D levels.
The findings suggest, but do not prove, that low vitamin D raises cardiovascular risk, says study researcher Kevin Fiscella, MD, MPH, of the University of Rochester School of Medicine and Dentistry.
Fiscella and co-researcher Peter Franks, MD, of the University of California at Davis, published their study in the January/February issue of the Annals of Family Medicine.
Fiscella points out that vitamin C, vitamin E, and beta-carotene were all thought to lower heart attack and stroke risk just a few years ago. But the early excitement was not borne out in clinical trials.
Vitamin D: How Much Do You Need?
Vitamin D deficiency has traditionally been associated with bone and muscle weakness, but recent studies also suggest that it may contribute to a host of other conditions including diabetes, autoimmune diseases, and even certain cancers.
"We really don't know what the optimal levels are at this point, or if there is a downside to taking double or triple the recommended amount," he says.
The National Osteoporosis Foundation recommends that adults under 50 get 400 to 800 international units (IU) of vitamin D a day and that older adults get 800 to 1,000 IU.
Current federal nutrition guidelines consider 200 IU of vitamin D daily adequate for children and adults up to age 50 and 400-600 IU daily adequate for older adults.
But a government advisory panel is reviewing this recommendation and is expected to revise it later this year.
James H. O'Keefe, MD, who directs the preventive cardiology program at the Mid America Heart Institute in Kansas City, Mo., considers the current recommendations far too low.
"Three out of four Americans are not getting enough vitamin D," he tells WebMD. "In my opinion, 1,000 IU to 2,000 IU a day is probably safe for anyone to take. That may be enough for some people but not for others."
He says African-Americans and other dark-skinned people may need even more vitamin D to avoid deficiency.
Milk and other dairy products are good dietary sources of vitamin D, as are oily fish such as salmon, tuna, and mackerel. But it would be difficult, if not impossible, to get enough vitamin D from food sources alone, O'Keefe says.