Association between dietary antioxidant vitamins intake/blood level and risk of gastric cancer

We aimed to systematically evaluate the association between dietary intake/blood levels of antioxidant vitamins (vitamin C, vitamin E, β‐carotene, and α‐carotene) and gastric cancer risk. Systematic literature searches were conducted until April 2013 in Pubmed and Embase to identify relevant studies. Either a fixed‐ or a random‐effects model was adopted to estimate overall odds ratios (ORs). Dose–response, meta‐regression, subgroup, and publication bias analyses were applied. Forty articles were finally included in the present study. Higher dietary intake of vitamin C, vitamin E, β‐carotene, and α‐carotene was inversely associated with gastric cancer risk (for vitamin C, pooled OR = 0.58, 95% CI 0.51–0.65; for vitamin E, pooled OR = 0.65, 95% CI 0.57–0.74; for β‐carotene, pooled OR = 0.59, 95% CI 0.49–0.70; for α‐carotene, pooled OR = 0.69, 95% CI 0.52–0.93). Subgroup analyses suggested the effects of these antioxidant vitamins were different in gastric cancer subtypes. As indicated by dose–response analysis, a 100 mg/day increment of vitamin C intake conferred an OR of 0.78 (95% CI 0.67–0.90); a 15 mg/day increment of vitamin E intake conferred an OR of 0.79 (95% CI 0.66–0.94); and a 5 mg/day increment in β‐carotene intake conferred an OR of 0.80 (95% CI 0.60–1.04). No significant association was observed between blood vitamin C, α‐tocopherol, γ‐ tocopherol, β‐carotene and α‐carotene levels and gastric cancer risk. In conclusion, dietary intake of vitamin C, vitamin E, β‐carotene and α‐carotene was inversely associated with gastric cancer risk while no such association was observed for blood levels of these antioxidant vitamins, thus the results should be interpreted cautiously.