Meta-Analysis
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World J Gastroenterol. Nov 7, 2014; 20(41): 15413-15422
Published online Nov 7, 2014. doi: 10.3748/wjg.v20.i41.15413
Consumption of garlic and risk of colorectal cancer: An updated meta-analysis of prospective studies
Ji-Yi Hu, Yi-Wang Hu, Jiao-Jiao Zhou, Meng-Wen Zhang, Dan Li, Shu Zheng
Ji-Yi Hu, Yi-Wang Hu, Jiao-Jiao Zhou, Meng-Wen Zhang, Dan Li, Shu Zheng, Cancer Institute, Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, Zhejiang Province, China
Author contributions: Hu JY and Zheng S designed the study; Hu JY, Hu YW, Zhou JJ, Zhang MW and Li D performed the literature search and data extraction; Hu JY and Hu YW analyzed the data; Hu JY and Zheng S wrote the paper; all authors have read and approved the final version to be published.
Correspondence to: Shu Zheng, MD, FACS, Cancer Institute, Key laboratory of Cancer Prevention and Intervention, China National Ministry of Education, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, Zhejiang Province, China. zhengshuzuci@163.com
Telephone: +86-571-87784501 Fax:+86-571-87214404
Received: March 24, 2014
Revised: May 17, 2014
Accepted: June 12, 2014
Published online: November 7, 2014
Processing time: 231 Days and 2.7 Hours
Abstract

AIM: To conduct an updated meta-analysis of prospective studies addressing the association between garlic consumption and colorectal cancer.

METHODS: Eligible cohort studies were identified by searching MEDLINE (PubMed) and screening the references of related articles published up to October 2013. Meta-analyses were conducted for colorectal cancer in relation to consumption of raw and cooked (RC) garlic and garlic supplements, separately. The summary relative risks (RR) with 95%CI were calculated using fixed-effects or random-effects model depending on the heterogeneity among studies.

RESULTS: A total of 5 prospective cohort studies were identified. In contrast to the previous meta-analysis, no significant associations were found between consumption of RC garlic (RR: 1.06; 95%CI: 0.95-1.19) or garlic supplements (RR: 1.12; 95%CI: 0.96-1.31) and risk of colorectal cancer. A non-significant protective effect of garlic supplement intake against colorectal cancer was observed in females (RR: 0.84; 95%CI: 0.64-1.11), but the opposite was the case in males (RR: 1.24; 95%CI: 0.96-1.59).

CONCLUSION: Consumption of RC garlic or garlic supplements is not significantly associated with reduced colorectal cancer risk.

Keywords: Colorectal cancer; Garlic; Garlic supplement; Cancer prevention; Meta-analysis

Core tip: Garlic is consumed worldwide as a food additive and botanical supplement. The previous meta-analysis, mostly based on case-control studies, suggested that garlic consumption was associated with reduced colorectal cancer risk; however, our updated meta-analysis based on high-quality prospective studies showed no significant association between garlic consumption and risk of colorectal cancer. The recommendation of garlic consumption as a nutrition intervention against colorectal cancer should be cautious.