Journal Name:
Lipids
Article Title:
Comparison of n-3 polyunsaturated fatty acids from vegetable oils, meat, and fish in raising platelet eicosapentaenoic acid levels in humans.
Date Written:
1999
Volume:
34
Number:
NA
Page:
s309
Author(s):
Article:
The objective of the present trial was to investigate the ability of ovolacto vegetarian and vegan groups to convert short chain omega 3 to longer chain omega 3 fatty acids. Results from observational work has shown that the n-3/n-6 ratio in plasma and platelet phospholipids (PL) was significantly lower in both ovolacto vegetarian and vegan groups compared with meat-eaters. Collagen and ADP-stimulated whole blood platelet aggregation showed a significant opposite trend to both plasma and platelet PL n-3/n-6 ratios. Plasma 11-dehydro thromboxane B 2 (11-dehydro TXB2), a stable metabolite of the pro-inflammatory eicosanoids, TXA2, was found to be higher in ovolacto vegetarian and vegan groups compared with meat-eaters. These data suggest that the vegetarians had a potentially greater thrombotic risk than the omnivore subjects. The aim of this study was thus to investigate whether male vegetarian subjects who consumed an increased dietary ratio of alpha-linolenic acid (ALA)/linoleic acid exhibited an increased n-3/n-6 polyunsaturated fatty acid (PUFA) ratio in platelet PL, plasma PL, and triacylglycerol (TAG), decreased plasma TX levels, and reduced platelet aggregability compared with their habitual diet.
Seventeen healthy male vegetarian subjects aged 22-48 yr were recruited. During the study, all subjects maintained their habitual vegetarian diets, except a proportion of dietary fat was replaced with provided vegetable oils and oil-based margarines. All 17 subjects consumed a low n-3/n-6 ratio diet (safflower oil and safflower oil-based margarine) for 14 d, following which they consumed either a moderate n-3/n-6 ratio diet (canola oil and canola oil-based margarine) or a high n-3/n-6 ratio diet (flaxseed oil and flaxseed oil-based margarine) for 28 days. Subjects were requested to refrain from consuming fish during the 42 day of the intervention.
Omega 3 eicosapentaenoic acid (EPA), total n-3 PUFA levels, and n-3/n-6 ratio were significantly increased, while the omega 6 arachadonic acid (AA) AA/EPA ratio decreased, following either a canola or a flaxseed oil-based diet compared with a safflower oil-based diet. Omega 3 docosapentaenoic acid was significantly increased following the flaxseed oil-based diet compared with the safflower oil-based diet. There was no significant increase in omega 3 docosahexaenoic acid (DHA) in these lipids. No statistically significant differences between the study diet period were observed on the various thrombotic risk factors.
These data were compared with a previous study in which 23 adult omnivore subjects consumed 350 g/d of lean red meat for 2 wk (EPA intake = 70 mg/d) or 133 g/d of Atlantic salmon for 2 wk (EPA intake = 847 rag/d). These diets also led to significant changes in platelet EPA levels (0.5 to 0.7% on the red meat diet, and 0.4 to 1.9% on the salmon diet, as percentage of total platelet PL). The results indicate that canola and flaxseed oils have similar effects on the fatty acid profile of platelet PL and plasma lipid. The greatest increases in n-3 PUFA occurred with flaxseed oil which had the highest ALA content. ALA from the vegetable oils (canola and flaxseed) used as a dietary fat for daily food preparation had a beneficial effect on alteration of fatty acid profiles of platelet PL and plasma lipids in vegetarian populations and should be encouraged as sources of omega 3 fatty acids. Longer-term studies may be necessary to establish effects of plant source n-3 PUFA on hemostatic function in vegetarians.
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