"Oxidized" cholesterol, a particularly harmful form of the fat common in Western diets, could speed the clogging of arteries and increase the risk of heart disease according to researchers at the San Francisco Veterans Affairs Medical Center (SFVAMC) and the University of California San Francisco (UCSF). In studies with rabbits, the investigators have demonstrated that a diet containing oxidized cholesterol may increase the amount of fatty deposits on blood vessel walls.
It is widely known that substantial quantities of oxidized cholesterol are present in the American diet, according to the researchers. Large amounts of oxidized cholesterol are found in fried and processed foods, which constitute the bulk of many fast food menus.
The results of the study, which appears in the current issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association, dramatically illustrate the negative effects of oxidized cholesterol. The researchers studied two groups of genetically similar rabbits.
Both groups were fed a low cholesterol diet but one group had a small amount of oxidized cholesterol added. After only 12 weeks, the rabbits on the oxidized cholesterol diet developed a 100 percent increase in fat deposits in their aortas -- the major artery that carries blood from the heart. According to Ilona Staprans, PhD, head of the SFVAMC Lipid Research Laboratory and principal investigator of the study, the small amount of added oxidized cholesterol (25 milligrams a day), is equivalent to amounts found in an average American1s diet. While it is uncertain whether the results of these animal studies are applicable to humans, the researchers believe their findings are clearly cause for concern.
"With the popularity of fried foods and the wide-spread fast food industry, oxidized fats are common in the Western diet and could contribute to heart disease," says Staprans. "Our research leads us to believe that heated cholesterol-containing foods may be considered a risk factor for heart disease." When consumed, oxidized cholesterol is absorbed and combines with fat particles in the blood known as lipoproteins. As these lipoproteins containing oxidized cholesterol travel through the blood stream, they can adhere to the walls of arteries and form fatty deposits called plaque. When plaque builds up in an artery, it slowly blocks blood flow the way a rusty pipe restricts the travel of water. If the flow of blood becomes too slow and the heart doesn1t receive enough oxygen, heart disease may develop.
Co-investigators in the study were Joseph H. Rapp, MD, SFVAMC chief of vascular surgery and UCSF professor in residence; Xian-Mang Pan, MD, SFVAMC research associate; and Kenneth R. Feingold, MD, SFVAMC department of metabolism and UCSF professor in residence. The research was funded by the U.S. Department of Veterans Affairs and the Pacific Vascular Research Foundation.