BACKGROUND: Recent studies have shown that dietary total antioxidant capacity (D-TAC) may affect risk of cancer; however, findings are conflicting. Hence, we aimed to summarize the current evidence on the association between D-TAC and risk of cancer.METHODS: We searched the online databases of PubMed, ISI Web of Science, Scopus, ProQuest, Science Direct and Embase until October 2018 using relevant keywords. To pool data, fixed- or random-effects models were used where appropriate.RESULTS: In total, 19 studies including 8 prospective and 11 case-control studies with 721429 individuals and 16159 cases of cancer were included in the current systematic review and meta-analysis. Combining 15 effect sizes from 6 prospective and 8 case-control studies revealed a significant inverse association between D-TAC (obtained from ferric reducing antioxidant power (FRAP)) and risk of cancer (combined effect size: 0.86, 95% CI: 0.81-0.92, P < 0.001). Such inverse association was also seen for D-TAC obtained from other methods including trolox equivalence antioxidant capacity (TEAC) (combined effect size: 0.80, 95% CI: 0.70-0.90, P < 0.001), total radical trapping antioxidant parameter (TRAP) (combined effect size: 0.69, 95% CI: 0.62-0.78, P < 0.001) and oxygen radical absorbance capacity (ORAC) (combined effect size: 0.72, 95% CI: 0.52-1.00, P = 0.04). In addition, a significant non-linear association was found between D-TAC (based on FRAP and TRAP) and cancer risk (P-nonlinearity<0.001). Based on linear dose-response meta-analysis, a-10 mmol/day increase in FRAP and a-5 mmol/day increase in TRAP and TEAC were associated with 9%, 17% and 14% reduction in risk of cancer, respectively. Furthermore, D-TAC was inversely associated with risk of colorectal (combined effect size: 0.82, 95% CI: 0.75-0.89, P < 0.001), gastric (combined effect size: 0.63, 95% CI: 0.53-0.73, P < 0.001), and endometrial cancer (combined effect size: 0.78, 95% CI: 0.69-0.89, P < 0.001).CONCLUSIONS: Diet with high antioxidant capacity might have protective effects against cancer.
Antioxidants Diet