A nutritional supplement during preconception and pregnancy increases human milk vitamin D but not B-vitamin concentrations

Background & aims: Optimal maternal vitamin status during pregnancy and lactation is essential to support maternal and infant health. For instance, vitamin D₃ is involved in infant bone development, and B-vitamins are involved in various metabolic processes, including energy production. Through a double-blind randomised controlled trial, we investigated the effects of maternal supplementation from preconception throughout pregnancy until birth on human milk (HM) concentrations of vitamin D₃ and B-vitamins. In addition, we aimed to characterise longitudinal changes in milk concentrations of these vitamins.

Methods: Both control and intervention supplements contained calcium, iodine, iron, β-carotene, and folic acid, while the intervention also contained zinc, vitamins B₂, B₆, B₁₂, and D₃, probiotics, and myo-inositol. HM samples were collected across 4 time points from 1 week to 3 months post-delivery from 158 mothers in Singapore, and 7 time points from 1 week to 12 months from 180 mothers in New Zealand. HM vitamin D was quantified using supercritical fluid chromatography and B-vitamins with mass spectrometry. Potential intervention effects on HM vitamins D₃, B₂, B₆, and B₉, as well as other B-vitamin (B₁ and B₃) concentrations were assessed using linear mixed models with a repeated measures design.

Results: Over the first 3 months of lactation, HM 25-hydroxyvitamin D₃ concentrations were 20% (95% CI 8%, 33%, P = 0.001) higher in the intervention group, with more marked effects in New Zealand. There were no observed intervention effects on HM concentrations of vitamins B₁, B₂, B₃, B₆, and B₉. In New Zealand mothers, longitudinally, vitamin D₃ concentrations gradually increased from early lactation up to 12 months, while vitamins B₁ and B₂ peaked at 6 weeks, B₃ at 3 weeks, and B₆ and B₉ at 3 months.

Conclusions: Maternal supplementation during preconception and pregnancy increased HM vitamin D, but not B-vitamin concentrations in lactation. Further studies are required to examine the discrete benefits of vitamin D supplementation starting preconception vs during pregnancy, and to further characterise the effects of supplementation on later offspring health outcomes.

Clinical trial registration: Registered at ClinicalTrials.gov on the 16 July 2015 (identifier NCT02509988); Universal Trial Number U1111-1171-8056. This study was academic-led by the EpiGen Global Research Consortium.