Study Shows Low Levels of Vitamin D May Explain Racial Gap in Cardiovascular Risk
By Salynn Boyles
WebMD Health News
Reviewed By Louise Chang, MD
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.
Darker-skinned people produce less vitamin D from the sun than those with lighter skin, and studies show that blacks are far more likely to have lower levels of the vitamin than whites.
Several recent studies also suggest that low levels of vitamin D are associated with an increased risk for heart attack and stroke.
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.
Compared to everyone else in the study, the quarter with the lowest vitamin D levels had a 40% higher risk of dying from heart attacks, strokes, and other heart-related events.
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.
"The message is that vitamin D deficiency might be a major contributor to cardiovascular deaths," he tells WebMD. "We really need clinical trials to understand this association."
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.
"We have had a lot of false hopes with various nutrients and vitamins," he says.
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 autoimmune diseases, and even certain cancers.
Fiscella says it is too soon to recommend taking vitamin D supplements to improve heart health.
"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.
Healthy Heart Resources
Fiscella, K. Annals of Family Medicine, January/February, 2010; vol 8: online edition.
Kevin Fiscella, MD, MPH, professor of family medicine, department of community and preventive medicine, University of Rochester School of Medicine and Dentistry, N.Y.
National Institutes of Health: "Dietary Supplement Fact Sheet: Vitamin D."
National Osteoporosis Foundation: "Vitamin D Recommendations."
News release, American Academy of Family Physicians.
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