British Journal of Nutrition

Research Article

Long-term monounsaturated fatty acid diets reduce platelet aggregation in healthy young subjects

Ruth D. Smitha1, Colette N. M. Kellya1, Barbara A. Fieldinga2, David Hautona2, K. D. Renuka R. Silvaa1, Margaretha C. Nydahla1, George J. Millera3 and Christine M. Williamsa1 c1

a1 Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, University of Reading, Reading RG6 6AP, UK

a2 Oxford Lipid Metabolism Group, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX2 6HE, UK

a3 Epidemiology and Medical Care Unit, Medical Research Council, Wolfson Institute of Preventative Medicine, Charter House Square, London EC1M 6BQ, UK

Abstract

The aim of the present study was to compare the response of a range of atherogenic and thrombogenic risk markers to two dietary levels of saturated fatty acid (SFA) substitution with monounsaturated fatty acids (MUFA) in students living in a university hall of residence. Although the benefits of such diets have been reported for plasma lipoproteins in high-risk groups, more needs to be known about effects of more modest SFA-MUFA substitutions over the long term and in young healthy adults. In a parallel design over 16 weeks, fifty-one healthy young subjects were randomised to one of two diets: (1) a moderate-MUFA diet in which 16 g dietary SFA/100 g total fatty acids were substituted with MUFA (n 25); (2) a high-MUFA diet in which 33 g dietary SFA/100 g total fatty acids were substituted with MUFA (n 26). All subjects followed an 8-week run-in diet (reference diet), with a fatty acid composition close to the UK average values. There were no differences in plasma lipid responses between the two diets over 16 weeks of the study with similar reductions in total cholesterol (P <0·001) and LDL-cholesterol (P<0·01) in both groups; a small but significant reduction in HDL-cholesterol was also observed in both groups (P<0·01). Platelet responses to ADP (P<0·01) and arachidonic acid (P<0·05) differed with time on the two diets; at 16 weeks, platelet aggregatory response to ADP was significantly lower on the high-MUFA than the moderate-MUFA (P<0·01) diet; ADP responses were also significantly lower within this group at 8 (P<0·05) and 16 (P<0·01) weeks compared with baseline. There were no differences in fasting factor VII activity (factors VIIc and VIIag), fibrinogen concentration or tissue-type plasminogen activator activity between the diets. There were no differences in postprandial factor VIIc responses to a standard meal (area under the curve) between the diets after 16 weeks, but postprandial factor VIIc response was lower than on the high-MUFA diet compared with baseline (P<0·01). In conclusion, a high-MUFA diet sustains potentially beneficial effects on platelet aggregation and postprandial activation of factor VII. Moderate or high substitution of MUFA for SFA achieves similar reductions in fasting blood lipids in young healthy subjects.

(Received July 18 2002)

(Revised May 20 2003)

(Accepted June 02 2003)

Correspondence:

c1 *Corresponding author: Professor Christine M. Williams, fax +44 118 931 0080, email c.m.williams@reading.ac.uk