Cardiovascular risk factors in vegetarians: Normalization of hyperhomocysteinemia with vitamin B-12 and reduction of platelet aggregation with n-3 fatty acids

Hyperhomocysteinemia in association with vitamin B-12 deficiency, and incre ased platelet aggregation, probably due to dietary lack of n-3 fatty acids, constitute cardiovascular risk factors frequently observed in vegetarians. We tested if administration of vitamin B-12 normalizes the concentration o f total plasma homocysteine, and if intake of eicosapentaenoic (20:5n-3) an d docosahexaenoic (22:6n-3) fatty acids modulates platelet function in a po pulation of lactoovovegetarians. One week after a single intramuscular inje ction of cyanocobalamin (10000 mug) in 18 individuals, serum vitamin B-12 i ncreased from 149+/-63 pg/mL to 532+/-204 pg/mL (p<0.0001) and total tHcy d ropped from 12.4+/-4.7 to 7.9+/-3.1 <mu>mol/L (p<0.0001). Ten of fourteen o f these vegetarians completed an 8-week supplementation with 700 mg/day of each eicosapentaenoic and docosahexaenoic acids. Increased incorporation of these fatty acids into plasma lipids was observed in all of them, together with a significant reduction in maximum percentage or slope of platelet ag gregation with all the agonists tested (ADP, epinephrin, collagen, arachido nic acid). No significant change in bleeding time was observed after n-3 fa tty acid trial. Supplementation with vitamin B-12 and n-3 fatty acids corre cts hyperhomocysteinemia and reduces platelet reactivity to agonists in veg etarians. Whether this supplementation improves the already reduced cardiov ascular morbidity and mortality associated with vegetarian diet has yet to be demonstrated. (C) 2000 Elsevier Science Ltd. All rights reserved.