High-fat diets that lower cholesterol.

High-fat diets that lower cholesterol

Even people at risk of heart disease achieved major changes in lood fats -- including reductions in total serum cholesterol -- while maintaining a tasty, high-fat diet. The trick, say researchers from Ohio State University at Columbus, is limiting saturated fats to less than 8 percent of total calories.

Nutritionist Jean T. Snook and her co-workers studied changes in the blood lipid profiles of 20 men, aged 27 to 47, who slowly cycled through four diets, each deriving 40 percent of its calories from fat. The researchers fed the men a typical U.S. diet -- high in butter and saturated fats -- for two weeks, then switched them to a vegetable-oil-dominated diet for the next five weeks. After a seven-week, Thanksgiving-to-New Year's reprieve from the supervised, cafeteria-supplied meals, the men returned for phase two of the trials: another two-week butter diet, followed by five weeks on a different vegetable-oil-dominated menu.

In the butter diet, 21 percent of each day's calories came from saturated fat. The corn oil diet delivered 19 percent of its calories as polyunsaturated fats, and the sunflower oil menu derived 28 percent of its calories from monounsaturated fats. In all diets except the corn oil regimen, polyunsaturated fats represented less than 7 percent of calories. Similarly, except on the butter diet, saturated fats were limited to less than 8 percent of calories. Both limits match guidelines recommended in the National Research Council's landmark "Diet and Health" report (SN: 4/22/89, p.250).

When the men switched from the butter diet to either of those dominated by vegetable oils, their total serum cholesterol plummeted 16 to 21 percent from a starting average of 240 milligrams per deciliter of blood. Low-density lipoprotein (LDL) cholesterol dropped 21 to 26 percent, and triglycerides fell 10 to 21 percent. Since high-density lipoprotein (HDL) cholesterol values did not change, the ratio of total cholesterol to HDL cholesterol -- a highly predictive risk fator in heart disease (SN: 9/9/89, p.171) -- actually improved by at least 20 percent in these men. (Scientists think high-density lipoproteins help remove cholesterol from the blood.) And in a separate experiment, adding 300 mg of cholesterol to the vegetable oil diets--for a total intake of 480 mg cholesteral daily -- "basically had no effect" on these serum cholesterol changed.

"Diet modifications designed to lower serum lipids could place most of the emphasis on reducing saturated fats rather than total fat intake," Snook and her co-workers conclude.