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.
Dr Gong Yang and colleagues from China investigated whether soy food intake is associated with colorectal cancer risk.
The team prospectively examined 68,412 women aged 40 to 70 years and free of cancer and diabetes at enrollment.
Usual soy food intake was assessed at baseline, and reassessed during the first follow-up, through in-person interviews with a validated food-frequency questionnaire.
|5-g/d increment in intake of soy foods was associated with an 8% reduction in risk|
|American Journal of Clinical Nutrition|
The team excluded the first year of observation to minimize lifestyle changes related to preclinical disease.
The researchers identified 321 incident colorectal cancer cases during a mean follow-up of 6 years.
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 was associated with an 8% reduction in risk.
Women in the highest tertile of intake had a multivariate relative risk of 0.7 compared with those in the lowest tertile.
This inverse association was primarily confined to postmenopausal women.
Similar results were also found for intakes of soy protein and isoflavones.
Dr Yang’s team concluded, “This prospective study suggests that consumption of soy foods may reduce the risk of colorectal cancer in postmenopausal women.”