Periconceptional intakes of methyl donors and other micronutrients involved in one-carbon metabolism may further reduce the risk of neural tube defects in offspring: a United States population-based case-control study of women meeting the folic acid recommendations

Background: Neural tube defects (NTDs) still occur among some women who consume 400 mu g of folic acid for prevention. It has been hypothesized that intakes of methyl donors and other micronutrients involved in one-carbon metabolism may further protect against NTDs. Objectives: To investigate whether intakes of vitamin B6, vitamin B12, choline, betaine, methionine, thiamine, riboflavin, and zinc, individually or in combination, were associated with NTD risk reduction in offspring of women meeting the folic acid recommendations. Methods: Data were from the National Birth Defects Prevention Study (United States population-based, case-control). We restricted deliveries between 1999 and 2011 with daily periconceptional folic acid supplementation or estimated dietary folate equivalents >= 400 mu g. NTD cases were live births, stillbirths, or terminations affected by spina bifida, anencephaly, or encephalocele (n = 1227). Controls were live births without a major birth defect (n = 7095). We categorized intake of each micronutrient as higher or lower based on a combination of diet (estimated from a food frequency questionnaire) and periconceptional vitamin supplementation. We estimated NTD associations for higher compared with lower intake of each micronutrient, individually and in combination, expressed as odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for age, race/ethnicity, education, and study center. Results: NTD associations with each micronutrient were weak to modest. Greater NTD reductions were observed with concurrent higher-amount intakes of multiple micronutrients. For instance, NTD odds were similar to 50% lower among participants with >= 4 micronutrients with higher-amount intakes than among participants with <= 1 micronutrient with higher-amount intake (adjusted OR: 0.53; 95% CI: 0.33, 0.86). The strongest reduction occurred with concurrent higher-amount intakes of vitamin B6, vitamin B12, choline, betaine, and methionine (adjusted OR: 0.26; 95% CI: 0.09, 0.77) compared with <= 1 micronutrient with higher-amount intake. Conclusions: Our findings support that NTD prevention, in the context of folic acid fortification, could be augmented with intakes of methyl donors and other micronutrients involved in folate metabolism.