Effects of MTHFR A1298C polymorphism on peripheral blood folate concentration in healthy populations: a meta-analysis of observational studies

Background and Objectives: Methylenetetrahydrofolate reductase (MTHFR) irreversibly converts 5,10- methylenetetrahydrofolate to 5-methyltetrahydrofolate, which is the main form of folate used in the body. Previous studies suggest that MTHFR polymorphism influences folate metabolism, but conflicting results are reported. We performed a meta-analysis to accurately characterize the association between MTHFR A1298C polymorphism and peripheral blood folate concentration in healthy populations. Methods and Study Design: Studies focusing on MTHFR A1298C polymorphism and folate concentrations were identified and subjected to a metaanalysis using Review Manager 5.1. Standard mean differences (SMD) with 95% confidence intervals (95% CI) were used to assess the association between these variables. Results: A total of 14 studies with 5616 healthy individuals were included in this meta-analysis. Significant differences in folate concentration were found in the MTHFR homozygote model (SMD=0.12, 95% CI=0.00-0.24, I2=17%, p=0.04) and the dominant model (SMD=0.07, 95% CI=0.01-0.14, I2=22%, p=0.02) in the general population excluding the elderly. While abnormal folate concentrations are more common in elderly, no association between MTHFR A1298C polymorphism and peripheral blood folate concentration was found in the meta-analysis when elderly were included. Conclusions:This meta-analysis indicates that, in the general population excluding the elderly, the C allele of MTHFR 1298 polymorphism is associated with the risk for an increased folate concentration.