Key Findings:
This study assessed the ability of lactoovovegetarians to convert ALA to 20- and 22-carbon n-3 long-chain PUFAs by desaturation and elongation. A diet with a low ratio of n-3 to n-6 PUFAs (n-3:n-6) can cause a reduced tissue n-3:n-6 [ie, increased ratio of arachidonic acid (AA; 20:4n-6) to eicosapentaenoic acid (EPA; 20:5n-3)], which may promote production of thromboxane A2 (a potent platelet aggregating agent), leading to increased thrombosis. The results showed that canola and linseed oils have a similar effect on the fatty acid profile of platelet phospholipids and plasma lipids. The use of ALA may have a beneficial effect on increasing the n-3 PUFA content of platelet phospholipids and plasma lipids in vegetarian populations.
ABSTRACT:
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 an increased amount of dietary alpha-linolenic acid (ALA) showed any changes in their tissue profile of PUFAs, plasma thromboxane concentrations, platelet 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) for 14 d; they then consumed either a moderate-ALA diet (containing canola oil and canola oil–based margarine) or a high-ALA diet (containing linseed oil 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), whereas the ratio of arachidonic acid to eicosapentaenoic acid was decreased (P < 0.05), in platelet phospholipids, plasma phospholipids, and triacylglycerols after either the moderate-ALA or high-ALA diet compared with the low-ALA diet. No significant differences were observed in thrombotic risk factors. Conclusion: ALA from vegetable oils (canola and linseed) has a beneficial effect on n-3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males. (Authors abstract)