Dietary folic acid intake, 13 genetic variants and other factors with red blood cell folate concentration in pregnancy-preparing population.

Purpose: This study aims to evaluate a combined effect of dietary folic acid intake, multiple genetic polymorphisms in folate metabolism, and other environmental factors on red blood cell (RBC) folate concentration in pregnancy-preparing population.

Methods: 519 pregnancy-preparing subjects (260 couples) were investigated. Dietary intake was measured by 3-day dietary recalls. 13 Single Nucleotide polymorphisms (SNPs) reported in association with one-carbon metabolism including the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C were genotyped. RBC folate concentration was measured using chemiluminescence assay. Hierarchical regression was applied for covariate selection. Factors showed significance(p < 0.0125) on RBC folate level was included for prediction model construction and R² estimation. Validation cohort analysis was performed as post-hoc analysis if applicable.

Results: The median RBC folate was 212.8 ng/ml. Only 10% took folic acid supplementation within three months. Based on hierarchical selection, folic acid supplementation, genetic polymorphism (especially TT genotype of MTHFR C677T), serum folate level were determinants of the variance of RBC folate concentrations, with adjusted R² of 0.178-0.242. MTHFR A1298C polymorphism, sex difference with other socio-demographic and lifestyle factors (age, BMI, alcohol drinking, smoking, education, occupation) explained little to change in RBC folate level. Validation in another sub-cohort(n = 8105) had adjusted R² of 0.273.

Conclusion: In pregnancy-preparing subjects, folic acid supplementation, serum folate level and TT allele of MTHFR C677T polymorphism were determinants of the total variance of RBC folate level, which explained 19.8% variance in our subjects and 27.3% in the validation cohort. Food folate intake, sex and other environmental factors explained little to RBC folate level.