Prospective cohort study of soy food intake and colorectal cancer risk in women.
BACKGROUND
Soy and some of its constituents, such as isoflavones, have been shown to have cancer-inhibitory activities in experimental studies. Data from epidemiologic studies linking usual soy food intake with colorectal cancer are limited and inconsistent.


OBJECTIVE
The objective was to investigate whether soy food intake is associated with colorectal cancer risk.


METHODS
We prospectively examined 68,412 women aged 40-70 y and free of cancer and diabetes at enrollment. Usual soy food intake was assessed at baseline (1997-2000) and reassessed during the first follow-up (2000-2002) through in-person interviews with a validated food-frequency questionnaire. We excluded the first year of observation to minimize lifestyle changes related to preclinical disease.


RESULTS
During a mean follow-up of 6.4 y, 321 incident colorectal cancer cases were identified. After adjustment for potential confounding factors, total soy food intake was inversely associated with colorectal cancer risk. Each 5-g/d increment in intake of soy foods as assessed by dry weight [equivalent to approximately 1 oz (28.35 g) tofu/d] was associated with an 8% reduction in risk (95% CI: 3%, 14%). Women in the highest tertile of intake had a multivariate relative risk of 0.67 (95% CI: 0.49, 0.90) compared with those in the lowest tertile (P for trend = 0.008). This inverse association was primarily confined to postmenopausal women. Similar results were also found for intakes of soy protein and isoflavones.


CONCLUSIONS
This prospective study suggests that consumption of soy foods may reduce the risk of colorectal cancer in postmenopausal women.
Yang
Gong
G
Department of Medicine, Vanderbilt Epidemiology Center and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37203-1738, USA. gong.yang@vanderbilt.edu
Shu
Xiao-Ou
XO
Li
Honglan
H
Chow
Wong-Ho
WH
Cai
Hui
H
Zhang
Xianglan
X
Gao
Yu-Tang
YT
Zheng
Wei
W
D000328:Adult; D000368:Aged; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D005247:Feeding Behavior; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D017698:Postmenopause; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D045730:Soy Foods; D013025:Glycine max; D011795:Surveys and Questionnaires