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Résumé (anglais)

Optimal function of one carbon (1-C) metabolism is necessary during reproduction as it supplies 1-C units for purposes of synthesis or methylation of nucleic or amino acids. Maintaining nutrient status of the methyl vitamins folate, choline, vitamins B6 and B12 is crucial to prevent the nutrient imbalances linked to increased risk of neural tube (NTD) and other birth defects. There is little understanding of whether or not pregnancy and folic acid (FA) supplementation influence 1-C metabolism–for example shunting toward DNA synthesis in pregnancy. Using red blood cell forms as a mechanism to evaluate partitioning of folate early in erythropoiesis we examined the RBC folate forms in pregnant women consuming 1 mg of FA and non-pregnant women consuming 0, 1 and 5 mg supplemental FA (n=26). We found that neither pregnancy nor level of FA altered the relative distributions of the folate in RBC indicating no preferment for DNA synthesis. We then investigated if a comprehensive list of socio-demographic and lifestyle factors would improve our ability to predict if a woman was more likely to have RBC folate concentrations associated with NTD protection in women of childbearing years (WCBY), thereby removing the necessity for a blood sample (n=101). We found that a FA supplement of 200 ug/d or a multivitamin consumed every other day, taking into account alcohol intake while controlling for ethnicity, can effectively discriminate RBC folate concentrations associated with NTD protection 73% of the time. Lastly, since the majority of women do not use multivitamins regularly, we systematically investigated the specific foods that contribute to dietary folate, vitamin B12, vitamin B6 and choline intakes of WCBY using nationally representative data from the Canadian Community Health Survey 2.2 (n=4308). We found heavy reliance on FA fortified foods for folate intake and animal products (37- 94%) for B6, choline and B12 intakes. The mean daily choline intake in WCBY was 238 mg with ~99 % of WCBY having intakes below Adequate Intakes. Our investigation suggests that status of the methyl nutrients is sensitive to a number of factors influencing 1-C metabolism.