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

Abstract

Background: Vegetarians have lower platelet and plasma concentrations of nϪ3 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 ␣-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 nϪ3 PUFAs, and the ratio of nϪ3 to nϪ6 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 nϪ3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males.Am J Clin Nutr 1999;69:872-82. KEY WORDSVegetarian diet, ␣-linolenic acid, linoleic acid, platelet fatty acid, plasma fatty acid, polyunsaturated fatty acids, hemostatic factors, thrombosis, lipoprotein lipids, men INTRODUCTIONThe predominant polyunsaturated fatty acid (PUFA) in the Western diet is linoleic acid (LA; 18:2nϪ6), which is commonly found in vegetable seed oils. LA is the parent fatty acid of the nϪ6 series PUFAs, which can be converted in vivo to 20-and 22-carbon nϪ6 long-chain PUFAs. ␣-Linolenic acid (ALA; 18:3nϪ3) is less abundant than LA; however, it is also present in vegetable oils and is the precursor of 20-and 22-carbon nϪ3 long-chain PUFAs. Omnivores can obtain their 20-and 22-carbon nϪ3 long-chain PUFAs either from dietary ALA or directly by consumption of fish, eggs, or animal products (1). Lactoovovegetarians can gain a limited amount of 20-and 22-carbon nϪ3 long-chain PUFAs from milk, dairy products, and eggs. Because animals can convert ALA to 20-and 22-carbon nϪ3 long-chain PUFAs and plants cannot, there are no 20-or 22-carbon nϪ3 long-chain PUFAs in plant-based vegan diets. Thus, vegans must rely totally on endogenous synthesis from ALA by desaturation and elongation. A diet with a low ratio of nϪ3 to nϪ6 PUFAs (nϪ3:nϪ6) can cause a reduced tissue nϪ3:nϪ6 [ie, increased ratio of arachidonic acid (AA; 20:4nϪ6) to eicosapentaeno...

Replacing cows' with sheep's dairy fat lowers plasma cholesterol concentration in participants consuming dairy fat-rich diets

“…Ingestion of substantially larger amounts of alpha-linolenic acid (9 g per day for 4 week) increased C20:5n-3 and C22:5n-3 in plasma triacylglycerol (by 0.3 and 0.5% of total fatty acids, respectively); however, 22:6n-3 remained unchanged (Cunnane et al, 1995). The complete lack of change in blood levels of 22:6n-3 with ingestion of alpha-linolenic acid is a consistent finding of feeding trials lasting less than several months (Chan et al, 1993;Li et al, 1999) and argues that some of the participants in our study ate more fishFa source of all three preformed long chain n-3 polyunsaturated fatsFduring the sheep diet. The combination of increased alpha-linolenic acid from the sheep-dairy products and increased fish intake could explain the fatty acid results.…”

Dietary fatty acids and human health

“…ALNA supplementation can significantly increase the level of ALNA and EPA in plasma and cells [1,15,65,68,111,112,116] but ALNA supplementation does not increase (and may even decrease) DHA and in some studies does not reduce AA levels [74,99]. One study has demonstrated that ALNA and long-chain omega-3 PUFA supplementation have equivalent effects on haemostatic factors [31], however other studies have failed to observe significant effects of dietary ALNA on haemostatic variables [61,68]. In addition, unlike EPA and DHA, ALNA supplementation has no effect on plasma TAG concentrations [31,100] except at very high levels of dietary intake.…”

Dietary α-linolenic acid increases the platelet count in ApoE−/− mice by reducing clearance

“…[7][8][9][10][11][12][13] Although the Alpha Omega Trial did not show a significantly different event rate among patients receiving LCn3-FA in addition to state-of-the-art therapy for myocardial infarction, 14 previous studies and subgroup analyses demonstrated a beneficial effect of omega (v)-3 FA. 11,15 An inexpensive and abundantly available alternative to marine-derived v-3 is the plant-derived alpha (a)-linolenic acid (ALA) that, by itself or by chain elongation to LCn3-FA EPA, DPA, and DHA, has a number of beneficial effects. However, these effects are somewhat less well characterized than those of the LCn3-FAs.…”