Dr Lawson believes that existing evidence strongly supports that garlic supplementation causes a lasting reduction in serum total cholesterol levels beyond 3 months. We respectfully disagree about the definitiveness of current evidence. He argues that the few available randomized controlled trials of 5 to 6 months' duration do not show persistent cholesterol level–lowering effects because all but one of these trials have had low-dissolution allicin release. We believe it is possible that differences in allicin release among various garlic preparations might explain some intertrial variability. However, 4 of the trials that looked at 20- to 24-week outcomes were conducted with preparations that purposely contained negligible amounts of allicin, and there were no significant mean differences in lipid levels between these trials and those that tested preparations that purportedly contained allicin. Further, all of the trials had significant shortcomings, other than differences in allicin content, that could account for variant outcomes. In addition, Dr Lawson argues that there are positive statistical associations between the duration of garlic consumption and the degree of reduction of serum total cholesterol levels if one concentrates on trends within treatment groups of individual studies rather than on pooled standardized mean differences of the trials. This alternative interpretation does not consider between-group differences and discounts the benefit of having placebo comparisons.
Ackermann R, Mulrow C. Duration of the Hypocholesterolemic Effect of Garlic Supplements—Reply. Arch Intern Med. 2001;161(20):2505. doi: