OBJECTIVE: To evaluate the hypocholesterolemic effect of an enteric-coated garlic supplement standardized for allicin-releasing potential in mild to moderate hypercholesterolemic patients. METHODS: A double-blind randomized, placebo-controlled intervention study was conducted in 46 hypercholesterolemic subjects who had failed or were not compliant with drug therapy. Each subject was given dietary counseling to lower fat intake and enteric-coated Australian garlic powder tablets with 9.6 mg allicin-releasing potential or matching placebo tablets. RESULTS: After 12 weeks, the garlic supplement group (n=22) had a significant reduction in total cholesterol (TC, -0.36 mmol/L. -4.2%) and LDL-cholesterol (LDL-C, -0.44 mmol/L, -6.6%) while the placebo group (n=24) had a non-significant increase in TC (0.13 mmol/L, 2.0%) and LDL-C (0.18 mmol/L, 3.7%). HDL-cholesterol was significantly increased in the placebo group (0.09 mmol/L, 9.1%), compared to the garlic group (-0.02 mmol/L, -0.9%). and no significant difference in triglycerides or in LDL/HDL ratio was observed between groups. CONCLUSIONS: The study demonstrates that enteric-coated garlic powder supplements with 9.6 mg allicin-releasing potential may have value in mild to moderate hypercholesterolemic patients when combined with a low fat diet. Taken with other evidence, the efficacy of garlic for lipoprotein metabolism might require allicin bioavailability to be enhanced through the use of, for example, an enteric-coated dose form. If this is the case, the possibility remains that greater hypocholesterolemic efficacy may be evident at a higher allicin dose. Also noteworthy in this study was a small reduction in energy intake with garlic compared with placebo, attributable to reduction in fat, carbohydrate and alcohol intakes. This may also have contributed to the effects on blood lipids. This study suggests that garlic supplementation has a cholesterol-lowering effect, which may be mediated by direct action of a biologically active compound or compounds and in part through the effect on food and nutrient intake.