Therefore, the lack of gene–environment interaction between the effects of ADH1B and ALDH2 gene polymorphisms and alcohol consumption on the risk of breast cancer in this study (Table 2 and 4) suggests that the carcinogenic effect of acetaldehyde for breast cancer, if present, must be weak, and that other mechanisms explain the carcinogenic effect of alcohol. Here, ALDH2 is linked to breast carcinoma.