TUESDAY, June 15, 2010 (HealthDay News) -- Eating a Mediterranean-style diet might improve an important measure of heart function, a new study of twins shows.
The research was conducted with twins to try to eliminate the possible effect of genetics as much as possible, explained Dr. Jun Dai, an assistant professor of nutrition and epidemiology at Indiana University, and lead author of a report released online June 15 in advance of publication in the July print issue of Circulation: Cardiovascular Quality and Outcomes.
The Mediterranean-style diet differs from standard American fare by featuring a low content of saturated fats and high intake of fish, fruits, vegetables, olive oil, nuts and cereals, with a glass or two of wine a day. Many studies have linked it to a lower incidence of heart disease.
This latest research included 276 male twins, some identical, some fraternal; fraternal twins share 50 percent of their genes while identical twins share 100 percent. The researchers measured their heart rate variability, the variation in the time interval between heartbeats in everyday life. "Higher variability reflects good function of the heart," Dai explained.
The men in the study reported their food preferences on a questionnaire, and were scored by how closely their intake matched that of a Mediterranean diet. Their heart activity was measured and recorded with a portable, battery-operated electrocardiogram monitor.
The study found that higher Mediterranean diet scores were related to greater variability in heart rate. On a nine-point scale, every one-unit difference was associated with a greater heart rate variability of 3.9 percent to 13 percent. This equates to a 9 percent to 14 percent reduction in the risk of heart-related death, the report said.
The results can't be generalized to everyone, because all the twins in the study were white males, the report said. "But this should encourage more people to choose a healthy diet and others in the health-care system to promote it," Dai said.
Heart rate variability is well-known to be related to cardiac health, said Dr. Gordon F. Tomaselli, chief of cardiology at Johns Hopkins University and a spokesman for the American Heart Association. Low variability means that the autonomic system that controls heart rate might not be able to respond properly to increased demand or that the heart "is in crisis mode all the time," he explained.
The results have an inevitable range of uncertainty, since they depended on self-reports of dietary habits, and the physical link between diet and heart rate variability is not completely clear, Tomaselli said. "But all other things being equal, a more Mediterranean-like diet appears to swing the balance to the healthy side of the autonomic system," he added.
Tomaselli said he tries to steer people toward a Mediterranean-type diet, without necessarily using the term. "I see a lot of people who I think should eat more fish and reduce caloric intake, to eat more fruits and vegetables, to use canola or olive oil when they use oil, and to back off salty foods," he said.
Details and variations on the theme of the Mediterranean diet are outlined by the American Heart Association.
SOURCES: Jun Dai, M.D., Ph.D., professor, nutrition and epidemiology, Indiana University, Bloomington, Ind.; Gordon F. Tomaselli, M.D., professor, medicine, and chief, cardiology, Johns Hopkins University, Baltimore; June 15, 2010, Circulation: Cardiovascular Quality and Outcomes, online
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