The effect of replacing dietary saturated fat with polyunsaturated or monounsaturated fat on plasma lipids in free-living young adults.
OBJECTIVE
To examine, in free-living adults eating self-selected diets, the effects on plasma cholesterol of substituting saturated fat rich foods with either n-6 polyunsaturated or monounsaturated fat rich foods while at the same time adhering to a total fat intake of 30-33% of dietary energy.


METHODS
Two randomised crossover trials.


METHODS
General community.


METHODS
Volunteer sample of healthy free-living nutrition students at the University of Otago. Trial I, n=29; and trial II, n=42.


METHODS
In trials I and II participants were asked to follow for 2(1/2) weeks a diet high in saturated fat yet with a total fat content that conformed to nutrition recommendations (30-33% energy). During the 2(1/2) week comparison diet, saturated fat rich foods were replaced with foods rich in n-6 polyunsaturated fats (trial I) whereas in trial II the replacement foods were rich in monounsaturated fats. Participants were asked to maintain a total fat intake of 30-33% of energy on all diets.


METHODS
Energy and nutrient intakes, plasma triglyceride fatty acids, and plasma cholesterol.


RESULTS
When replacing saturated fat with either n-6 polyunsaturated fat or monounsaturated fat, total fat intakes decreased by 2.9% energy and 5.1% energy, respectively. Replacing saturated fat with n-6 polyunsaturated fat (trial I) lowered plasma total cholesterol by 19% [from 4.87 (0.88) to 3.94 (0.92) mmol/l, mean (s.d.)], low density lipoprotein cholesterol by 22% [from 2.87 (0.75) to 2.24 (0.67) mmol/l], and high density lipoprotein cholesterol by 14% [from 1.39 (0.36) to 1.19 (0.34) mmol/l], whereas replacing saturated fat with monounsaturated fat (trial II) decreased total cholesterol by 12%, low density lipoprotein cholesterol by 15%, and high density lipoprotein cholesterol by 4%, respectively. The change in the ratio of total to high density lipoprotein cholesterol was similar during trial I and trial II.


CONCLUSIONS
Young adults are very responsive to dietary-induced changes in plasma cholesterol even when an isocaloric replacement of saturated fat with n-6 polyunsaturated or monounsaturated fat is not achieved. Replacing saturated fat with either n-6 polyunsaturated or monounsaturated fat is equally efficacious at reducing the total to high density lipoprotein cholesterol ratio.


BACKGROUND
University of Otago, Meadow Lea Ltd.
Hodson
L
L
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Skeaff
C M
CM
Chisholm
W A
WA
D000328:Adult; D002784:Cholesterol / Q000097:blood*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D018592:Cross-Over Studies; D004041:Dietary Fats / Q000008:administration & dosage* / Q000494:pharmacology; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage* / Q000494:pharmacology; D002149:Energy Intake; D005229:Fatty Acids, Monounsaturated / Q000008:administration & dosage* / Q000494:pharmacology; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D016896:Treatment Outcome; D014280:Triglycerides / Q000097:blood*
D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004041:Dietary Fats; D004042:Dietary Fats, Unsaturated; D005229:Fatty Acids, Monounsaturated; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D014280:Triglycerides; D002784:Cholesterol