Vitamin D status and metabolism in pregnant, lactating, and nonpregnant women consuming controlled intakes of vitamin D (959.7)

As part of a 10‐wk controlled feeding study, we investigated the impact of reproductive state on circulating levels of vitamin D metabolites among pregnant (n=26, 27wk gestation), lactating (n=28, 5wk postpartum), and nonpregnant (n=21) women consuming a daily intake of 300 IU vitamin D derived from food (90IU/d) and a prenatal supplement (200IU/d). At study‐end, serum 25‐hydroxyvitamin D (25[OH]D, mean±SD nmol/L) was higher in pregnant women (98±32) than lactating (81±19, P =0.044) and nonpregnant (78±25, P =0.032) women. Similar results were achieved after controlling for confounding factors such as season in a multivariate model. Notably, 300 IU (half of the current RDA) achieved 25(OH)D levels above the RDA target value of 50nmol/L in most of study participants (92%). Study‐end plasma 1,25‐dihydroxyvitamin D (mean [95% CI] pmol/L) was ~2 times higher in pregnant women (303 [252‐364]) than lactating (139 [116‐167], P <.0001) and nonpregnant (163 [139‐191], P <.0001) women. Similarly, study‐end vitamin D binding protein levels (mean [95% CI] mcg/mL) were ~1.8 times higher in pregnant women (370 [291‐470]) than lactating (161 [131‐198], P <.0001) and nonpregnant (205[166‐255], P =0.001) women. In sum, pregnancy dramatically influenced circulating vitamin D metabolites under controlled intakes of vitamin D and related nutrients (e.g., calcium and phosphorus). Grant Funding Source : USDA, AEB‐ENC and the Beef Checkoff