Folate intake and the risk of breast cancer: an up-to-date meta-analysis of prospective studies

Epidemiological studies focusing on the association between folate and breast cancer risk reported inconsistent findings. We conducted a systematic search of the literature using PubMed and EMBASE databases. A total of 23 prospective studies involving 41,516 cases and 1,171,048 individuals were included for meta-analysis. Folate intake may decrease the risk of oestrogen receptor (ER) negative (-) and ER-/progesterone receptor (PR)-breast cancer, with pooled risk ratios (RRs) of 0.88 [95% confidence interval (CI): 0.78-1.00] and 0.82 (95% CI: 0.68-0.97), respectively. An increment of folate intake of 100 mu g per day was associated with a deceased risk of ER- (RR = 0.94, 95% CI: 0.88-0.99) and ER-/PR- (RR = 0.90, 95% CI: 0.85-0.97) breast cancer. Moreover, high folate intake may have preventive effects against breast cancer in premenopausal women (RR = 0.94, 95% CI: 0.88-1.00) and individuals with moderate or high levels of alcohol consumption (RR = 0.82, 95% CI: 0.72-0.94).