Background: Prevention of cardiovascular disease by modifying its major risk factors, including serum cholesterol levels, is an important strategy. Regular intake of garlic has been suggested, but its impact on cholesterol levels has been inconsistent.
Objective: A systematic review to critically summarize the evidence on the effect of garlic on serum cholesterol.
Methods: We carried out a comprehensive search of the Cochrane Library, MEDLINE, EMBASE, electronic publishing sites, reference lists of relevant papers and manual searches of relevant journals from inception to March 2008. We contacted experts and local manufacturers and distributors of garlic products to identify additional studies. To evaluate the effects of garlic on cholesterol levels in both healthy and hypercholesterolaemic subjects, randomized controlled trials of garlic ranging from 11 to 24 weeks in duration were included. Data were extracted and trial quality was assessed independently by two reviewers. The data were meta-analysed.
Results: Thirteen trials including 1056 subjects were eligible for the meta-analysis. Overall, administration of garlic did not show any significant difference in effects on all outcome measures examined when compared with placebo. Garlic therapy did not produce any statistically significant reduction in serum total cholesterol level (mean difference, −0·04 mmol/L; 95% CI −0·15 to 0·07 mmol/L), LDL-cholesterol level (mean difference, 0·01 mmol/L; 95% CI −0·10 to 0·11 mmol/L), triglycerides level (mean difference, −0·05 mmol/L; 95% CI −0·17 to 0·06 mmol/L) or apolipoprotein B level (mean difference, −0·02 g/L; 95% CI −0·03 to 0·001 g/L). There was no difference between garlic and placebo on HDL-cholesterol level (mean difference, 0·01 mmol/L; 95% CI −0·03 to 0·05 mmol/L). As moderate to high heterogeneity exists among pooled studies, conclusive recommendations cannot be made at present on the actual effects of garlic therapy on serum cholesterol levels.
Conclusion: The available evidence from randomized controlled trial does not demonstrate any beneficial effects of garlic on serum cholesterol.