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, P dose-response =0.001, P nonlinearity = 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; I 2 = 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.