Consumption of garlic and risk of colorectal cancer: An updated meta-analysis of prospective studies

Table 1 Main characteristics of included studies

Ref.	Study	Country	Follow-up		Number of participants, age (yr)			Dietary	Study	Adjustment for confounders
			Start	End	Male	Female	Total	assessment	quality
Meng et al[7] (2013)	The Nurses’ Health Study (NHS)	United States	1984	June 2008	NA	76208 (1339 cases), 30-55 yr	76208 (1339 cases)	Validated FFQ	8	Age, BMI, smoking, history of colorectal cancer, history of endoscopy screening, regular aspirin use, physical activity, postmenopausal hormone use, beef, pork and lamb as a main dish, consumption of processed meat, alcohol consumption, energy-adjusted total calcium intake, total folate, total vitamin D intake, total energy intake
Meng et al[7] (2013)	The Health Professionals Follow-up Study (HPFS)	United States	1986	Jan 2008	45592 (1029 cases), 40-75 yr	NA	45592 (1029 cases)	Validated FFQ	8	Age, BMI, smoking, history of colorectal cancer, history of endoscopy screening, regular aspirin use, physical activity, postmenopausal hormone use, beef, pork and lamb as a main dish, consumption of processed meat, alcohol consumption, energy-adjusted total calcium intake, total folate, total vitamin D intake, total energy intake
McCullough et al[8] (2012)	The American Cancer Society Cancer Prevention Study (CPS) II Nutrition Cohort	United States	1999	June 2007	42824 (579 cases)	56876 (551 cases)	99700 (1130 cases)	Validated FFQ	9	Age, energy intake, gender, history of endoscopy, BMI, physical activity, smoking, alcohol consumption, NSAID use, PMH use, total calcium intake, fruits, vegetable and red/processed meat intake
Satia et al[9] (2009)	The VITamins And Lifestyle (VITAL) study	United States	Oct 2000-Dec 2002	Dec 2006	36516 (220 cases), 50-76 yr	39568 (208 cases), 50-76 yr	76084 (428 cases)	Validated FFQ	9	Age, gender, education, physical activity, fruit and vegetable consumption, BMI, NSAID use, sigmoidoscopy, history of arthritis
Sellers et al[23] (1998)	The Iowa Women's Health Study	United States	1986	Dec 1995	NA	35216 (241 cases), 55-69 yr	35216 (241 cases)	Validated FFQ	9	Age, total energy intake, history of colorectal polyps
Dorant et al[22] (1996)	The Netherlands Cohort Study	Netherlands	Sep 1986	Dec 1989	1525 (243 cases), 55-69 yr	1598 (200 cases), 55-69 yr	3223 (443 cases)	Validated FFQ	9	Age, gender, family history of intestinal cancer, education, smoking, previous history of chronic intestinal disease or cholecystectomy, vitamin C and beta-carotene intake

FFQ: Food frequency questionnaire; NSAID: Non-steroidal anti-inflammatory drugs.