Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men

Background: Vegetarians have lower platelet and plasma concentrations of n- 3 polyunsaturated fatty acids (PUFAs) than do omnivores, We recently showed that male vegetarians have higher platelet aggregability than do omnivores . Objective: We investigated whether male vegetarians (n = 17) who consumed a n increased amount of dietary alpha-linolenic acid (ALA) showed any changes in their tissue profile of PUFAs, plasma thromboxane concentrations, plate let aggregability, or hemostatic factors. Design: During the study, all subjects maintained their habitual vegetarian diets except that a proportion of dietary fat was replaced with vegetable oils and margarines that were provided. Initially, all subjects consumed a low-ALA diet (containing safflower oil and safflower oil-based margarine) f or 14 d; they then consumed either a moderate-ALA diet (containing canola o il and canola oil-based margarine) or a high-ALA diet (containing linseed o il and linseed oil-based margarine) for 28 d. Blood samples were collected at day 0 (baseline), day 14, and day 42. Results: Eicosapentaenoic acid, docosapentaenoic acid, total n-3 PUFAs, and the ratio of n-3 to n-6 PUFAs were significantly increased (P < 0.05), whe reas the ratio of arachidonic acid to eicosapentaenoic acid was decreased ( P < 0.05), in platelet phospholipids, plasma phospholipids, and triacylglyc erols after either the moderate-ALA or high-ALA diet compared with the low- ALA diet. No significant differences were observed in thrombotic risk facto rs. Conclusion: ALA from vegetable oils (canola and linseed) has a beneficial e ffect on n-3 PUFA concentrations of platelet phospholipids and plasma lipid s in vegetarian males.