Vitamins A, D, E, and K Intakes, Status, and Breastmilk Concentrations in Breastfeeding Women in Ireland

Background Fat-soluble vitamins A, D, E, and K are critical during the postpartum period for maternal recovery and infant development. Objectives To determine the concentrations of vitamins A, D, E, and K in maternal serum and breastmilk during the early postpartum period in breastfeeding women. Methods This was a secondary analysis of the WellFed 4-wk randomized controlled trial. Dietary recalls, serum, and breastmilk samples were collected from breastfeeding women at 4 and 8 wk postpartum ( n = 48). Vitamin status and metabolic biomarkers were quantified using liquid chromatography–tandem mass spectrometry and a clinical analyzer, respectively. Associations were analyzed using correlation, regression, and mediation analysis (PROCESS macro for SPSS; IBM Corp). Results Mean daily intakes for vitamins A, D, and E were 1230 ± 633 μg, 6.5 ± 4.6 μg and 13.3 ± 8.1 mg, respectively. All women were sufficient in serum retinol (2.1 ± 0.4, 2.1 ± 0.3 μmol/L), α-tocopherol (45.5 ± 9.5, 39.3 ± 8.7 μmol/L), and phylloquinone (1.0 ± 0.5, 1.1 ± 0.7 nmol/L) at weeks 4 and 8, respectively. Sixty-five percent of the cohort were vitamin D sufficient (61.7 ± 22.2 nmol/L, 56.7 ± 19.2 nmol/L). Vitamin A intake was positively associated with serum retinol concentrations ( r = 0.386, P = 0.012, adjusted P = 0.048). Breastmilk retinol (3.7 ± 1.2, 3.2 ± 1.1 μmol/L) and α-tocopherol (15.3 ± 7.4, 12.4 ± 5.1 μmol/L) concentrations were adequate at both timepoints, 25(OH)D 2 and 25(OH)D 3 were below the analytical detection limit. Serum and breastmilk α-tocopherol were correlated ( r = 0.363, P = 0.013, adjusted P = 0.026). Total cholesterol, triglycerides, and CRP predicted up to 56% of serum α-tocopherol variance. Conclusions Maternal serum concentrations of vitamins A, E, and K are adequate, whereas approximately two-thirds of women are vitamin D sufficient. Breastmilk vitamins A and E are adequate and higher than previously reported, whereas vitamin D metabolites are undetectable. Dietary intake is positively associated with serum vitamins A and D, whereas serum vitamin E is associated with lipid-related biomarkers and correlated with breastmilk α-tocopherol, highlighting a potential link between maternal metabolic health and vitamin E in breastmilk. This trial is registered at clinicaltrials.gov as NCT05924633 ( https://clinicaltrials.gov/study/NCT05924633 ).