Objective: To explore the association of soy food intake with breast cancer risk.
Methods: The epidemiological studies on soy food intake and breast cancer risk published from 1991 to April 2011 were searched from MEDLINE, Pubmed, EMBASE, Sci and CNKI databases. Meta-analysis was used to estimate the combined OR and 95% CI.
Results: Twenty eight studies were selected for the meta-analysis, including 23 case-control studies and 5 cohort studies. The overall analysis showed that soy food intake was inversely associated with the risk of breast cancer. The pooled OR was 0.86 (95% CI 0.78 - 0.94) for the combination of both study designs. However, the protective effect was only observed in case-control studies (the pooled OR = 0.86, 95% CI 0.77 - 0.95) but not in cohort studies. The protective effect of soy food intake on breast cancer risk was observed among studies conducted in Asian countries (OR = 0.76, 95% CI 0.67- 0.87), whereas no association was found in studies from Western countries (OR = 1.01, 95% CI 0.93-1.09). The further stratified analysis showed that the protective effect was only found in studies conducted in Asian countries (pooled OR = 0.76, 95% CI 0.65 - 0.89 for 14 case-control studies and OR = 0.81,95% CI 0.70 - 0.92 for 3 cohort studies, respectively). Additionally, the protective effect was only found among postmenopausal women but not among premenopausal women.
Conclusion: According to the meta-analysis of studies conducted in Asian countries, soy food intake is inversely associated with the risk of breast cancer among Asian women, especially based on the results of meta-analysis of case-control studies.