Season, adiposity, and baseline 25‐hydroxyvitamin D are predictors of maternal change in vitamin D status from 1 to 4 months postpartum

There is limited information on the vitamin D status of lactating women and the potential known predictors that contribute to vitamin D status during lactation. The objectives of this study were to determine vitamin D status of lactating women and identify key predictors of vitamin D status at 4 mo and change since 1 mo postpartum. Healthy, lactating mothers (n=44) in Montreal were recruited between May 2010 to April 2011. Fasted venous blood samples were collected at 1 and 4 mo postpartum for analyses of plasma 25‐hydroxyvitamin D (25(OH)D) by LIAISON® (Diasorin). Demographics, sun exposure, skin pigmentation, anthropometry, body composition, supplement use, and nutrition information were collected to identify predictors of 25(OH)D. From 1 to 4 mo postpartum, there was a significant decrease in 25(OH)D from 73.0 ± 21.6 nmol/L to 62.4 ± 18.3 nmol/L (p<0.001). At 1 mo, 7 (15.9%) mothers had 25(OH)D <50 nmol/L and 26 (59.1%) had 25(OH)D <75 nmol/L. At 4 mo, 9 (21.4%) mothers had 25(OH)D <50 nmol/L and 30 (71.4%) had 25(OH)D <75 nmol/L. Predictors of vitamin D status at 4 mo postpartum included weeks in the synthesizing period, vitamin D intake, and % change in body fat and predictors of change in 25(OH)D included baseline 25(OH)D, weeks in the synthesizing period, and % change in weight. These predictors are important to consider to prevent declines in vitamin D status during lactation. (Supported by CFDR).