Sulfated vitamin D metabolites represent prominent roles in serum and in breastmilk of lactating women.

Background: Concentrations of vitamin D (VitD) and 25-hydroxyvitamin D (25OHD) in breastmilk are low despite the essential role of VitD for normal infant bone development, yet additional metabolic forms of vitamin D may be present. This study evaluates the contribution of sulfated vitamin D metabolites, vitamin D ₃ -sulfate (VitD ₃ -S) and 25-hydroxyvitamin D ₃ -sulfate (25OHD ₃ -S) for lactating women and assesses the response to high-dose VitD ₃ supplementation.
Methods: Serum and breastmilk were measured before and after 28 days with 5000 IU/day VitD ₃ intake in 20 lactating women. Concentrations of VitD ₃ -S and 25OHD ₃ -S in milk, and 25OHD ₂ , 25OHD ₃ , 25OHD ₃ -S, VitD ₃ and VitD ₃ -S in serum were determined by mass spectrometry.
Results: Baseline vitamin D status was categorized as sufficient (mean ± SD serum 25OHD ₃ 69 ± 19 nmol/L), and both serum VitD ₃ and 25OHD ₃ increased following supplementation (p < 0.001). 25OHD ₃ -S was 91 ± 19 nmol/L in serum and 0.47 ± 0.09 nmol/L in breastmilk. VitD ₃ -S concentrations were 2.92 ± 0.70 nmol/L in serum and 6.4 ± 3.9 nmol/L in breastmilk. Neither sulfated metabolite significantly changed with supplementation in either serum or breastmilk.
Conclusions: Sulfated vitamin D metabolites have prominent roles for women during lactation with 25OHD ₃ -S highly abundant in serum and VitD ₃ -S distinctly abundant in breastmilk. These data support the notion that 25OHD ₃ -S and VitD ₃ -S may have physiological relevance during lactation and nutritional usage for nursing infants.
Competing Interests: Conflict of interest The authors have no commercial or financial conflicts of interest to declare.
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