No association between garlic intake and risk of colorectal cancer

Although experimental studies suggested beneficial role of garlic intake on colorectal carcinogenesis, limited prospective cohort studies have evaluated garlic intake in relation to colorectal cancer (CRC) incidence.

We followed 76,208 women in the Nurses' Health Study and 45,592 men in the Health Professionals Follow-up Study for up to 24 years and examined garlic intake and garlic supplement use in relation to CRC risk. Information on garlic intake and supplement use was assessed using a validated food frequency questionnaire and a Cox proportional hazard regression model was used to estimate the multivariable hazard ratio (MV-HR) and 95% confidence intervals (95% CIs).

We documented 2368 (1339 women and 1029 men) incident CRC cases and fo und no association between garlic intake and CRC risk; the MV-HRs (95% CIs) associated with garlic (1 clove or 4 shakes per serving) intake ≥ 1/day compared with < 1/month were 1.21 (0.94-1.57; p-trend = 0.14) for women and 1.00 (0.71-1.42; p-trend = 0.89) for men. The MV-HRs (95% CIs) of CRC for garlic supplement use, which was used in 6% of the participants in each study, were 0.72 (0.48-1.07) for women and 1.22 (0.83-1.78) for men.

Our prospective data do not support an important role of garlic intake or garlic supplement use in colorectal carcinogenesis.