Garlic at dietary doses does not impair platelet function

In vitro studies suggest that various bioactive constituents of Allium sativum (garlic) inhibit platelet function. The extent, however, to which dietary doses of garlic influence platelet function remains unknown. Therefore, we tested the effect of raw garlic on platelet function using point-of-care monitoring devices sensitive for cyclooxygenase I-inhibition and platelet adhesion.

Whole blood from 18 healthy volunteers was investigated before and 5 h after ingestion of the study medication consisting of Greek tsatsiki with 4.2 g raw garlic (verum), or Greek tsatsiki without garlic (placebo), in a randomized, crossover, observer-blinded, placebo-controlled study. The potential long-term effects of garlic were investigated in five volunteers after daily ingestion of 4.2 g of raw garlic over 1 wk. Platelet function was assessed with the Platelet Function Analyzer (PFA-100), impedance aggregometry (Multiplate), and thrombelastographic Platelet Mappingtrade mark. In vitro experiments were performed to prove the sensitivity of the assays to garlic-induced platelet inhibition.

Baseline values of platelet function were within normal range in all volunteers. Platelet function was not impaired by single and repeated oral consumption of Greek tsatsiki containing raw garlic in any point-of-care monitoring test used.

Platelet function is not impaired by single and repeated oral consumption of a dietary dose of garlic in healthy volunteers. Dishes containing socially acceptable doses of raw garlic are unlikely to increase the risk of perioperative bleeding. Further studies are warranted to determine the potential additive effects of platelet-inhibiting drugs combined with garlic and other herbs.