June 17, 1998 DALLAS, June 12 -- Eating a "Western" diet with lots of processed or fried foods can raise blood levels of "oxidized" cholesterol -- a particularly damaging form of cholesterol -- and could increase heart attack risk, scientists say.
Researchers report in this month's Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association about a study with rabbits that demonstrates blood levels of oxidized cholesterol match up with the quantity of oxidized cholesterol in the diet. The researchers found that in rabbits, the dietary oxidized cholesterol accelerated the process of atherosclerosis, or clogging of the blood vessels.
It is thought that blood vessels can oxidize cholesterol, leading to a collection of fat called plaque. But the new study finds that foods in the "Western" diet containing oxidized cholesterol -- cooked, fried or processed foods, meats, eggs and dairy products chief among them -- add to the overall oxidant load and can speed atherosclerosis.
"With the popularity of fried foods and the widespread fast-food industry, oxidized fats are common in the Western diet and could contribute to heart disease," says Ilona Staprans, Ph.D., of the Lipid Research Laboratory at the VA Medical Center in San Francisco.
Low-density lipoprotein (LDL) cholesterol is the "bad" form of cholesterol, but when it is oxidized, it can become even more dangerous. Oxidation occurs when cholesterol comes in contact with "free radicals," which are highly unstable, reactive oxygen molecules that circulate in the blood and damage tissues. Oxidized LDL cholesterol -- fat particles that have been combined with reactive oxygen -- plays a major role in the formation of artery-blocking plaque.
"Dietary oxidized cholesterol may contribute to atherogenesis, and dietary modification that reduces the intake of dietary oxidized cholesterol may have a role in the prevention and treatment of atherosclerosis," says Staprans.
The scientists examined two sets of rabbits with similar genetic makeup. One set was fed a higher amount of oxidized cholesterol. In studying the rabbits 12 weeks later, scientists found that small quantities of oxidized cholesterol (25 milligrams per day) increased atherosclerotic lesions by 100 percent in comparison to those rabbits not fed the extra oxidized cholesterol.
Co-authors include Xian-Mang Pan, Joseph H. Rapp and Kenneth R. Feingold.
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