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Teasing out dietary cholesterol's impact.

To defend their predilection for meat and dairy products, many people cite nutrition studies indicating that cholesterol consumption has little, if any, effect on cholesterol levels in the blood. Cardiologists counter by citing other studies linking dietary cholesterol to significant elevations in serum cholesterol and an increased risk of heart disease.

Who's right? Both, according to a preventive cardiologist from the University of Utah in Salt Lake City.

Paul N. Hopkins pooled data from 27 studies comparing dietary and serum cholesterol levels. Such meta-analyses hunt for trends stastically masked within the smaller, component studies. His findings, detailed in the June AMERICAN JOURNAL OF CLINICAL NUTRITION, appear to reconcile the seemingly divergent data on cholesterol. As a rule, the new analysis shows, the higher an individual's initial serum and dietary cholesterol levels, the less likely that raising or lowering dietary cholesterol will alter serum cholesterol.

So for most people, another egg or two per day should produce little change in blood cholesterol, Hopkins says. Why? Since the 400 milligrams of cholesterol contained in the typical U.S. daily diet have already saturated the body's need for the fat-like substance, any additional cholesterol accumulates in the liver rather than the blood. On the other hand, for people who typically eat less than 160 mg of cholesterol daily, such as Mexico's Tarahumara Indians, an extra egg or two might seriously spike their naturally low serum cholesterol.

Hopkins notes that genetics plays a far larger role than baseline cholesterol-consumption patterns in determining a person's responsiveness to dietary cholesterol -- accounting for about 50 percent of the variability seen in the populations he studied.

Within the diet, saturated fat remains the most important single influence on serum cholesterol levels. Hopkins says dietary cholesterol probably accounts for most of the remaining variability seen -- perhaps some 20 percent.

One of the biggest surprises, Hopkins observed, "is how easily the liver is saturated [with cholesterol]," a finding whose significance has not yet been studied. That saturation takes only 400 to 500 mg per day -- the equivalent of two eggs.
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Title Annotation:cholesterol's effect on the blood
Author:Raloff, Janet
Publication:Science News
Article Type:Brief Article
Date:Jun 13, 1992
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