University of Groningen Influence of daily 10-85 mu g vitamin D supplements during pregnancy and lactation on maternal vitamin D status and mature milk antirachitic activity Stoutjesdijk,

Pregnant and lactating women and breastfed infants are at risk of vitamin D deficiency. The supplemental vitamin D dose that optimises maternal vitamin D status and breast milk antirachitic activity (ARA) is unclear. Healthy pregnant women were randomised to 10 (n 10), 35 (n 11), 60 (n 11) and 85 (n 11) μg vitamin D3/d from 20 gestational weeks (GW) to 4 weeks postpartum (PP). The participants also received increasing dosages of fish oil supplements and a multivitamin. Treatment allocation was not blinded. Parent vitamin D and 25-hydroxyvitamin D (25(OH)D) were measured in maternal plasma at 20GW, 36GW and 4 weeks PP, and in milk at 4 weeks PP. Median 25(OH)D and parent vitamin D at 20GW were 85 (range 25–131) nmol/l and ‘not detectable (nd)’ (range nd–40) nmol/l. Both increased, seemingly dose dependent, from 20 to 36GW and decreased from 36GW to 4 weeks PP. In all, 35μg vitamin D/d was needed to increase 25(OH)D to adequacy (80– 249nmol/l) in >97·5% of participants at 36GW, while >85μg/d was needed to reach this criterion at 4 weeks PP. The 25(OH)D increments from 20 to 36GW and from 20GW to 4 weeks PP diminished with supplemental dose and related inversely to 25(OH)D at 20GW. Milk ARA related to vitamin D3 dose, but the infant adequate intake of 513 IU/l was not reached. Vitamin D3 dosages of 35 and >85μg/d were needed to reach adequate maternal vitamin D status at 36GW and 4 weeks PP, respectively.