Soy food consumption and risk of colorectal cancer in women Free

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Numerous in vitro and in vivo experiments have suggested potential cancer-inhibitory effects of soy and some of its constituents such as isoflavones. Data from epidemiological studies have been inconsistent and no study has prospectively evaluated the association of soy food intake with the incidence of colorectal cancer (CRC). We evaluated the association between soy food intake and CRC risk in a population-based prospective cohort study, the Shanghai Women’s Health Study, a cohort of 73,294 Chinese women aged 40 to 70 years and free of cancer and diabetes mellitus at baseline. Usual soy food consumption was assessed at baseline through in-person interviews using a validated food-frequency questionnaire. During a mean follow-up of 6 years, 251 incident CRC cases were identified. Total soy food intake at baseline was inversely associated with incident CRC (P for trend = 0.004). Women in the highest tertile of intake had a 43% reduction in CRC risk (multivariate relative risk [RR], 0.57; 95% confidence interval [CL], 0.39-0.83) compared with those in the lowest tertile. The reduction in risk was most evident when the analysis was restricted to CRC cases that were diagnosed 3 years after the baseline survey, with the corresponding RR of 0.43 (95% CI, 0.26-0.71; P for trend = 0.001). Similar results were also found for soy protein and isoflavone consumption. The inverse association with soy food consumption was observed for both colon and rectal cancer. In conclusion, this prospective study provides strong evidence that consumption of soy foods may reduce the risk of CRC.