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June 6, 2000 (Reston, Va.) -- Mice and monkeys fed monounsaturated fats -- such as olive oil -- develop more hardening of the arteries in major blood vessels than animals fed polyunsaturated fats, studies reported here at the American Heart Association meeting on Dietary Fatty Acids and Cardiovascular Health report.
"Our studies cast doubt on the much-touted 'Mediterranean diet,'" Lawrence Rudel, PhD, tells WebMD. "The animal studies speak very loudly that monounsaturated fats may not be beneficial." Rudel is professor of pathology and biochemistry at Wake Forest University School of Medicine in Winston-Salem, N.C.
Rudel and colleagues studied African green monkeys and a special strain of mice that were susceptible to hardening of the arteries, or atherosclerosis. They fed the animals a diet high in saturated, monounsaturated, or polyunsaturated fats, or standard lab chow formulated for these animals.
They found that animals on the saturated fat diet had the most low-density lipoprotein (LDL) -- or 'bad' cholesterol -- in their blood, and they also developed the most atherosclerosis in their major blood vessels. Those on the polyunsaturated fat diet had much less LDL in their blood, and those on the lab chow had the least. But those animals fed the monounsaturated fats also had high LDL levels and much more atherosclerosis than those consuming the polyunsaturated fats.
"Animal studies are so important, because we can control everything about their environment and change just the factor under investigation," says Rudel. "These studies raise the red flag of caution about consumption of monounsaturated fats."
Robert Eckel, MD, professor of medicine and physiology and biophysics at the University of Colorado, reviewed the studies for WebMD. "If I were a green monkey or a certain type of mouse, I'd definitely want to be eating the chow," he says. "But based on this research, I won't be supplementing my diet with a lot of olive oil."
"I don't think research has provided us with the last word yet, but I also am not comfortable with the wholesale recommendation of the Mediterranean diet," says Eckel, who is also chairman of the American Heart Association Nutrition Committee. "When we call this the Mediterranean diet, we're talking about a lifestyle, not just consumption of a certain type of fat. It could easily be another factor related to this diet that's responsible for the reduction in cardiovascular disease risk. More research is clearly needed."
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