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Good fats don't diminish "good" cholesterol.

Good Fats Don't Diminish "Good" Cholesterol

If you're trying to eat less saturated fat, and you're opting for heart-healthy polyunsaturates instead, here's good news from ARS researchers.

A recent study at the Western Human Nutrition Research Center suggests that polyunsaturates--the kind found in corn oil margarine, for example--don't lower your levels of the good HDL cholesterol.

The finding comes from tests of 11 healthy middle-aged men who volunteered at the San Francisco center.

James M. Iacono, center director, and chemist Rita M. Dougherty conducted the 3-month study. They say that although their conclusion agrees with findings of some experts, it conflicts with others that have suggested that the highly touted polyunsaturates may reduce good cholesterol.

"Although there was a dip in HDL's at the midpoint in our study," Iacono notes, "HDL levels went back up by the end of the experiment."

HDL's, or high-density lipoproteins, have been linked with a lowered risk of arteriosclerosis (hardening of the arteries). The so-called bad cholesterol, or low-density lipoprotein, is blamed for higher risk of heart disease. HDL and LDL are typically measured in the comprehensive blood test usually included in yearly physical exams. A total cholesterol of 200 or less and an HDL level of above 45 are generally recommended.

For part of the San Francisco study, volunteers followed the eating guidelines recommended by the American Heart Association--fats were no more than 30 percent of the day's calories. Each type of fat--saturated, monounsaturated, and polyunsaturated--made up about 10 percent of the day's total calories. Then, to pinpoint any effects the polyunsaturates might have on HDL cholesterol, Iacono and Dougherty lowered levels of polys to 3.8 percent for part of the study.

"Neither the 3.8 nor the 10 percent levels of polyunsaturates lowered HDL cholesterol for more than about 2 weeks," says Iacono. "In our new studies, we're looking for an explanation of why other researchers concluded that polyunsaturates lowered HDL's."

The ARS scientists relied on practical menus with typical foods that taste good and were easy to buy and prepare, yet were low in fat. Menus included, for instance, ham, turkey, meatloaf, baked fish, spaghetti, lasagna, or other familiar fare.

"Lowering the fat in your meals is often simply a matter of making easy substitutes at the supermarket or perhaps changing some of the ways you cook," says Dougherty. "You can cut fat calories if you trim visible fat off meat or choose lean meats and poultry. Or switch to low-fat of nonfat dairy products like skim milk or low-fat yogurt and reduced-fat sour cream.

"Instead of using butter for cooking or at the table," she adds, "choose polyunsaturated margarine like a vegetable-oil-based spread."

PHOTO : Center director James Iacono discusses food weighing procedures with laboratory assistant Jan Thomson. (K-4275-2)

PHOTO : Biological laboratory technician Elizabeth Denvir extracts samples for total lipid and fatty acid composition. (K-4276-3)

James M. Iacono and Rita M. Dougherty are with the USDA-ARS Western Human Nutrition Research Center, P.O. Box 29997, Presidio of San Francisco, CA 94129. Phone (415) 556-9697.
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Author:Wood, Marcia
Publication:Agricultural Research
Date:Jan 1, 1992
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