Increased dietary intake of α-linolenic acid (ALA) may be desirable to enrich tissue eicosapentaenoic acid (EPA; 20:5n-3) but competition between n-3 and n-6 fatty acids for enzymes involved in elongation and subsequent acylation will determine the relative proportions of phospholipid fatty acids. The aim of the present study was to examine the effects of altering the dietary ALA: linoleic acid (LA) ratio on rat platelet EPA and arachidonic acid (AA; 20:4n-6) concentrations. Sprague Dawley rats were fed on diets containing 30% total energy as fat with approximately 10% each of saturated, monounsaturated and polyunsaturated fatty acids with one of the following ALA:LA values; 1:7, l:4, l:1 or 1.3:1 (nine rats per group). After 4 weeks, blood was withdrawn from the abdominal aorta and platelet fatty acids analysed. The proportion of EPA was greater at the 1:1 and 1·3:1 ratios compared with the 1:7 and 1:4 (P < 0·05), and a decrease in AA was observed (P < 0·05) at the higher ratios. It was established that the platelet EPA:AA value increased (P < 0·05) as the dietary ALA:LA value increased
