Although vegan diets typically have a very favorable effect on a range of vascular risk factors, several independent groups have reported that the platelets of vegetarians are more sensitive to pro-aggregatory agonists than are those of omnivores. In light of clear and convincing evidence that platelet function has an important impact on risk for thromboembolic events, it is important to clarify the basis of platelet hyperaggregability in vegetarians. A dietary deficit of long-chain omega-3 fatty acids is not likely to explain this phenomenon, since most omnivore diets do not include enough of these fats to discernibly influence platelet function. A more plausible possibility is that relatively poor taurine status--a function of the facts that plants are devoid of taurine and the human capacity for taurine synthesis is limited - is responsible. Plasma taurine levels are lower, and urinary taurine excretion is substantially lower, in vegetarians than in omnivores. Platelets are rich in taurine, which functions physiologically to dampen the calcium influx evoked by aggregating agonists--thereby down-regulating platelet aggregation. Supplemental intakes of taurine as low as 400 mg daily have been reported to markedly decrease the sensitivity of platelets to aggregating agonists ex vivo. Although the average daily intake of taurine from omnivore diets may be only about 150 mg, it is credible to speculate that a supplemental intake of this magnitude could normalize the platelet function of vegetarians in the long term; in any case, this thesis is readily testable clinically. Taurine is just one of a number of nutrients found almost solely in animal products--"carninutrients"--which are rational candidates for supplementation in vegans.
Copyright 2004 Elsevier Ltd.