Administration of raw onion inhibits platelet-mediated thrombosis in dogs.

A number of studies suggest that dietary intake of onions is of benefit to cardiovascular health. Onion juice inhibits in vitro human platelet aggregation. To study the in vivo effect of onion on platelet aggregation, 11 dogs were prepared with mechanically damaged and stenosed coronary arteries. Periodic platelet-mediated thrombus formation followed by embolization produced cyclic flow reductions (CFR). In five dogs, 0.09 +/- 0.01 mL/kg onion juice administered intravenously abolished CFR within 20 min. This was followed by a 60 +/- 14% (P = 0.002) reduction in collagen-induced ex vivo whole-blood platelet aggregation. Six dogs were given 2.0 g/kg raw onion homogenate intragastrically. CFR were eliminated within 2.5-3 h in five of the dogs. This was accompanied by a 44 +/- 24% (P = 0.04) reduction in ex vivo aggregation. These findings suggest that the consumption of raw onion may help prevent platelet-mediated cardiovascular disorders. However, in vitro incubations of onion juice demonstrated that the platelet inhibitory response was significantly greater in dog blood than in human blood.