Background: Folate requirements increase during pregnancy and lactation. It is recommended that women who could become pregnant, are pregnant, or are lactating consume a folic acid (FA)-containing supplement. Objectives: We sought to determine breast-milk total folate and unmetabolized folic acid (UMFA) contents and their relation with FA-supplement use and doses in a cohort of Canadian mothers who were enrolled in the MIREC (Maternal-Infant Research on Environmental Chemicals) study. Design: Breast-milk tetrahydrofolate (THF), 5-methyl-THF, 5-formyl- THF, 5,10-methenyl-THF, and UMFA were measured with the use of liquid chromatography-tandem mass spectrometry (n = 561). Total daily supplemental FA intake was based on self-reported FA-supplement use. Results: UMFA was detectable in the milk of 96.1% of the women. Total daily FA intake from supplements was associated with breast folate concentration and species. Breast-milk total folate was 18% higher (P , 0.001) in supplement users (n = 401) than in nonusers (n = 160), a difference driven by women consuming .400 mg FA/d (P ≥ 0.004). 5-Methyl-THF was 19% lower (P , 0.001) and UMFA was 126% higher (P , 0.001) in supplement users than in nonusers. Women who consumed .400 mg FA/d had proportionally lower 5-methyl-THF and higher UMFA than did women who consumed ≥400 mg FA/d. Conclusions: FA-supplement use was associated with modestly higher breast-milk total folate. Detectable breast-milk UMFA was nearly ubiquitous, including in women who did not consume an FA supplement. Breast-milk UMFA was proportionally higher than 5-methyl-THF in women who consumed .400 mg FA/d, thereby suggesting that higher doses exceed the physiologic capacity to metabolize FA and result in the preferential uptake of FA in breast milk. Therefore, FA-supplement doses .400 mg may not be warranted, especially in populations for whom FA fortification is mandatory.

Additional Metadata
Keywords Breastmilk, Folate, Folic acid, Supplements, Unmetabolized folic acid
Persistent URL dx.doi.org/10.3945/ajcn.116.137968
Journal American Journal of Clinical Nutrition
Citation
Page, R. (Rachael), Robichaud, A. (André), Arbuckle, T.E. (Tye E.), Fraser, W.D. (William D.), & MacFarlane, A.J. (2017). Total folate and unmetabolized folic acid in the breast milk of a cross-section of Canadian women. American Journal of Clinical Nutrition, 105(5), 1101–1109. doi:10.3945/ajcn.116.137968