Vitamin or antioxidant intake (or serum level) and risk of cervical neoplasm: A meta-analysis

Background Case-control studies have reported the preventive effect of vitamin or antioxidant intake on cervical neoplasms such as cervical intraepithelial neoplasia (CIN) and invasive cervical cancer. However, the findings are inconsistent. Objective To investigate quantitative effects of vitamin or antioxidant intake on cervical neoplasm using meta-analysis. Search strategy We searched PubMed, EMBASE and the Cochrane Library in November 2008. All articles searched were independently reviewed and selected by two evaluators according to predetermined selection criteria. Selection criteria We included case-control studies reporting an association between vitamin or antioxidant intake (or serum level) and cervical neoplasm risk and reporting the adjusted odds ratios (OR) and 95% confidence intervals (CI), whenever possible. Data collection and analysis After retrieval of data from selected articles, we performed a meta-analysis using both fixed-effects and random- effects models. Main results Of 274 articles meeting our initial criteria, we included 22 case-control studies involving a total of 10 073 participants. In meta-analyses by type of vitamin or antioxidant, a significant preventive effect on cervical neoplasm was found in intakes of vitamin B12 (OR 0.35, 95% CI 0.19-0.63; n = 2), vitamin C (OR 0.67, 95% CI 0.55-0.82; n = 8), vitamin E (OR 0.56, 95% CI 0.35-0.88; n = 10), and beta-carotene (OR 0.68, 95% CI 0.55-0.84; n = 9). Authors' conclusions The findings of this meta-analysis indicate that overall, there were preventive effects of vitamin or antioxidant intake on cervical neoplasms in case-control studies.