Mohammad Parohan1, Alireza Sadeghi2, Seyed Reza Khatibi3, Morteza Nasiri4, Alireza Milajerdi5, Mahmoud Khodadost6, Omid Sadeghi7. 1. Gerash University of Medical Sciences, Gerash, Iran; Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. 2. Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. 3. Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran. 4. Department of Operating Room Technology, School of Paramedicine, Qom University of Medical Sciences, Qom, Iran; Student Research Committee, Department of Surgical Technology, School of Nursing and Midwifery, Shiraz University of Medical Sciences, Shiraz, Iran. 5. Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. 6. Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran (i) Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran; Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. 7. Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: omidsadeghi69@yahoo.com.
Abstract
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.
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.