Effects of 5-Methyltetrahydrofolic Acid Supplementation on Maternal Health and One-Carbon Metabolism During Lactation

This double-blind, randomized, placebo-controlled parallel trial evaluates the effects of maternal 5-methyltetrahydrofolate (5-MTHF) supplementation during breastfeeding. Thirty-six lactating mother-infant dyads will be randomized (1:1) to receive 5-MTHF or placebo for 6 weeks, stratified by infant sex and mode of delivery. Tolerability and adverse events will be monitored. Pre- and post-intervention assessments include breast milk one-carbon metabolites and oligosaccharides; maternal plasma one-carbon metabolites and metabolic health markers. Maternal mental health will be evaluated using the SCL-90-R questionnaire. A follow-up visit at 4 months will reassess infant anthropometry and microbiome outcomes.

Inclusion Criteria: * Maternal age between 18 and 42 years * Gestational age at birth ≥ 37 weeks. * Exclusive breastfeeding at enrollment. * Infant age 0-1 months Exclusion Criteria: * Multiple pregnancy * Presence of disease or malformations in the infant. * Weight-Standard Deviation Score \< -1 at enrollment. * Use of folate-containing multivitamin supplements during breastfeeding