Positive Health Online

Abstract

LI and colleagues, Department of Food Science, RMIT University, Melbourne, Victoria, Australia write that vegetarians have lower platelet and plasma concentrations of omega-3 polyunsaturated fatty acids (PUFAs) than do omnivores . The authors recently demonstrated that male vegetarians have higher platelet aggregability than omnivores. The authors studied whether male vegetarians who ate increased amounts of dietary alpha-linolenic acid (ALA) showed changes in their tissue PUFA profile, plasma thromboxane concentrations, platelet aggregability, or haemostatic factors.

Background

Methodology

17 men participated in the study. They maintained their usual vegetarian diets except that a proportion of dietary fat was replaced with substituted vegetable oils and margarines. All the men initially ate a low-ALA diet with safflower oil and safflower-based margarine for 14 days; thereafter they consumed either a moderate-ALA diet with canola oil and canola-based margarine, or a high-ALA diet with linseed oil and linseed oil-based margarine for 28 days. Blood samples were collected at baseline (day 0) and thereafter at days 14 and 42.

Results

Eicosapentaenoic acid (EPA), docosapentaenoic acid, total n-3 PUFAs and the ratio of n-3 to n-6 PUFAs were increased significantly; however the ratio of arachidonic acid to EPA was decreased in platelet phospholipids, plasma phospholipids and triacylglycerols following either the moderate-ALA or high-ALA diet compared with the low-ALA diet. There were no significant differences observed in thrombotic risk factors.

Conclusion

ALA from vegetable oils (canola and linseed) has a beneficial effect upon omega-3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males .

References

Li D et al. Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men. American Journal of Clinical Nutrition. 69(50: 872-82. May 1999.