Plasma lipid changes in young adult couples consuming polyunsaturated meats and dairy products

25 Young couples consumed either a saturated or polyunsaturated fat diet for a 20 wk period. The polyunsaturated beef, lamb, and dried products, high in linoleic acid, were produced by feeding ruminant animals 'protected lipid' feeds which prevent hydrogenation of fats in the rumen. The experimental design provided for 4 dietary groups: A) saturated diet for 20 wk; B) polyunsaturated diet for 20 wk; C) saturated diet for 10 wk then polyunsaturated diet for 10 wk; and D) polyunsaturated for 10 wk and then saturated diet for 10 wk. Polyunsaturated to saturated ratios (linoleic: total saturated fatty acids) for the diets were: prestudy, 0.43-0.56; saturated, 0.11-0.14; polyunsaturated, 0.56-0.62. Factors other than diet that appeared to affect cholesterol responses were carefully considered. During the initial 3 wk (regimentation period) plasma cholesterol concentrations decreased in all groups irrespective of diet. This was followed by 2 experimental periods in which the effects of the prescribed diets were readily apparent (response periods I and II). The final 4 wk of the study were characterized by diminishing compliance with the dietary discipline (abatement period). Subjects in each group (A,B,C,D) were subdivided into high and low on a basis of each group's initial median cholesterol level. Those in the high subgroups were very responsive to dietary changes whereas those in the low subgroups were not. Combined responses of high subjects were: polyunsaturated diet -10.7 mg/dl (P < 0.025), saturated diet, + 7.8 mg/dl (P < 0.05). Combined difference between saturated and polyunsaturated diets was 18.5 mg/dl or approximately a 10% cholesterol difference between the experimental polyunsaturated and saturated diets.