Dietary total antioxidant capacity and risk of breast cancer: a systematic review and dose-response meta-analysis of observational studies
Background Numerous epidemiological studies have suggested a potential association between the antioxidant capacity of the diet and the risk of breast cancer. Yet, these studies have yielded inconclusive results. We therefore conducted a systematic review and dose-response meta-analysis of observational studies to ascertain the association between dietary total antioxidant capacity (TAC) and breast cancer risk. Methods We systematically searched PubMed, Embase, Scopus, ISI Web of Science and China National Knowledge Infrastructure (CNKI) from database inception to May 2026, using predefined keywords to identify the relevant articles. Random-effects or fixed-effects models were used to pool relative risks (RRs) with corresponding 95% confidence intervals (CIs), as appropriate. Heterogeneity across studies was estimated using Cochran's Q test and the I2 statistics. Results Nine observational studies (seven case-control and two cohort studies), encompassing 33,981 participants, were included in the meta-analysis. Higher dietary TAC intake was significantly associated with a lower risk of breast cancer (RR = 0.86; 95%CI: 0.76–0.98; P = 0.022). Conversely, each standard deviation increment in dietary TAC intake was not associated with the risk of breast cancer (RR = 0.98; 95%CI: 0.94–1.02, P = 0.295). Also, the dose-response analysis showed a linear inverse association between dietary TAC and risk of breast cancer (RR = 0.988; 95%CI: 0.981–0.995, Pdose−response=0.001, Pnonlinearity = 0.546). The results of subgroup analyses showed a significant inverse association between dietary TAC and breast cancer in cohort studies, with low heterogeneity (P = 0.174; I2 = 18.9%). Conclusions This study indicates that higher dietary TAC intake is associated with a reduced risk of breast cancer. Further well-designed longitudinal studies are warranted to confirm these findings.