(OR09-07-24) The Effects of Vitamin D Supplementation on Sulfated Vitamin D Metabolites During Lactation

Objectives: Sulfated vitamin D metabolites are gaining attention in maternal health and infant nutrition. Pregnant women have elevated 25-hydroxyvitamin D-sulfate (25OHD-S) in serum that is nearly equivalent to 25-hydroxyvitamin D (25OHD) and infants have greater 25OHD-S than 25OHD, but it is not yet known how these metabolites are regulated during lactation. This study measured 25OHD-S and vitamin D-sulfate (VitD-S) in serum and breastmilk during lactation and investigated the effects of high-dose VitD supplementation on these sulfated metabolites.

Methods: Serum and breastmilk were assessed before and after 5000 IU/day VitD (cholecalciferol) supplementation in 20 lactating women. VitD-S and 25OHD-S were measured by LC-MS/MS.

Results: The vitamin D status at baseline was sufficient for 18 of 20 mothers with 25OHD of 69±19 nmol/L (mean ±SD). In serum, the sulfated 25OHD-S (92±19 nmol/L) was greater than 25OHD (P < 0.001) and did not change from supplementation (P=0.41), despite a significant increase of 25OHD (+27±10 nmol/L, P < 0.001). The VitD-S in milk (6.4±3.9 nmol/L) was greater than 25OHD-S in milk (P < 0.001), greater than precursors in serum (VitD, P=0.018; VitD-S, P<0.001), and did not change following supplementation (P=0.81).

Conclusions: Vitamin D sulfates are prominent metabolites in lactating mothers with 25OHD-S being abundant in serum and VitD-S being distinct in milk. 25OHD-S and VitD-S in either serum or breastmilk are not affected by VitD supplementation when mothers are already sufficient in VitD. From these results, it is evident that lactating women require additional vitamin D nutrition to accommodate increases in serum 25OHD-S and secretion of VitD-S into milk.

Funding Sources: The Mayo Clinic Parker D. Sanders & Isabella G. Sanders Professor of Family Medicine Endowment, Mayo Clinic Women’s Health Center Pilot Award Project