Vitamin C Supplementation For The Prevention Of Breast Cancer: A Systematic Review

Objective To evaluate the effect of vitamin C supplementation for preventing breastcancer in woman, and quantitatively estimate their dose-response relationships. MethodsLiterature included RCTs、Cohort studies and Case Control studies were electronicallysearched in The Cochrane Central Register of Controlled Trials (Central)、Cochranelibrary、Ovid Medline、CBM、CNKI from the date of their establishment to July2012,meanwhile the hand search was also performed to systemize the papers. According to theCochrane Handbook and Newscastle-Ottawa Quality Assessment Scale for systematicreviews, the studies were screened by two reviewers independently, the quality of theincluded studies was evaluated, the data were extracted, and meta-analysis was conductedusing Stata11.0soft ware. Results Overall15studies met the inclusion criteria.1RCT、6case-control studies and8cohort studies were included, involving12950cases incase-control study and8091cases and290597participants in cohort study.135womendeveloped incident invasive breast cancer in the supplement group and122women in theplacebo group in RCTs. Comparing the highest with the lowest intake by random effectmodel, people using supplementary Vitamin C reduced the breast cancer risk by3%(pooled RR=0.97，95%CI=0.92-1.03).There were no statistically significant effects of useVitamin C on breast cancer incidence. Tests for heterogeneity was46.9%（P=0.023）.Further subgroup analysis based on study design of case-control study did notchange the reduction, but the results became significant (pooled RR=0.91，95%CI=0.83-1).The dose-relationship shows that a negative dose–response relationshipwith the following time of supplementing vitamin C with risk of breast cancer. Comparingwith lasting for one year, people with3years has more less risk of breastcancer(P=0.038).The subgroup analysis based on menopause status, for the group of bothpremenopausal and postmenopausal shows that using supplement Vitamin C reduced thebreast cancer risk by9%(pooled RR=0.9，95%CI=0.83-0.97). Through the funnel plot、 the test of Begg and Egger, the publication bias may not be exist. Conclusion Ourmeta-analysis show that as an antioxidant vitamin, Vitamin C could use to prevent breastcancer as an auxiliary supplementary, and we could increase the following time in a saferange. Our study belongs to a Meta-analysis of observational studies, it has a high risk ofbias. It is suggested that this issue should be further studied in the future due to the lacklarge sample、multicentre and high grade RCTs, so that we can provide a more realisticand reliable evidence for people to prevent breast cancer.