Effect of consuming raw or boiled garlic on agonist‐induced ex vivo platelet aggregation: an open trial with healthy volunteers

Prior clinical trials with garlic powder (0.6–0.9 g dry wt/d; alliin = 8–12 mg) as tablets have shown inconsistent effects on induced platelet aggregation, using platelet rich plasma (PRP). No trials have been reported for raw or cooked garlic. The objective of this open trial was to determine if a high dose (near the maximum tolerable) of raw garlic (8 g fresh wt/d = 2.8 g dry wt; allicin content = 35 mg, from 88 mg alliin) or boiled garlic (8 g fresh wt/d; no allicin, alliin content = 84 mg), consumed in a sandwich, are able to inhibit induced platelet aggregation in 4 weeks in 9 healthy volunteers who showed normal antiaggregatory effects with aspirin (325 mg). Optical density was used to measure aggregation in PRP; electrical impedance was used for whole blood (WB). Low agonist concentrations were used to maximize antiaggregatory effects: collagen at 0.2 & 0.5 μg/mL (PRP) and 0.5 & 1.0 μg/mL (WB), ADP at 1.8 & 2.5 μM (PRP) and 5 & 12.5 μM (WB), and epinephrine at 1 μM (PRP). Results: raw garlic significantly decreased PRP aggregation to a small extent (5–8%) with all agonists, but it significantly increased collagen-induced WB aggregation (10–13%). Boiled garlic had no effects. Conclusions: the results are method dependent, but considering the large dose used, it appears unlikely that consumption of normal levels of raw or boiled garlic (1–3 g) will have an effect on ex vivo aggregation in healthy individuals. Funded by NIH/NCCAM.