Reproductive
Current breastfeeding and blood lead concentrations in U.S. premenopausal individuals: Results from NHANES 2003-2012 Kristen Upson* Mandy S. Hall Arianna V.E. Foster Nicole M. Talge Renee Heffron Robert O. Wright Julio Landero Michael Yin Flavia Matovu Quaker E. Harmon Kenneth Mugwanya Andrew Mujugira Chenxi Li Kristen Upson
To meet infant nutritional needs, calcium is mobilized from maternal skeleton during lactation. We hypothesized that greater bone remodeling with breastfeeding also increases mobilization of toxic metal lead (Pb) stored in bone to blood. We conducted a cross-sectional analysis using National Health and Nutrition Examination Survey (NHANES) 2003-2012 data. The study population comprised premenopausal individuals ages 20-42 with an intact uterus, ≥1 ovary, and blood Pb data (unweighted n=4,209). Accounting for the complex survey sampling, we used multivariable linear regression to estimate the percent difference in blood Pb levels and 95%CI by current breastfeeding status; we adjusted for age, education, smoking, alcohol use, NHANES year, 25-hydroxyvitamin D, calcium intake, energy intake, current hormonal contraceptive use, and pregnancy status. Those currently breastfeeding had a higher geometric mean Pb concentration (0.88 µg/dl, 95%CI: 0.80, 0.97) compared to others (0.77 µg/dl, 95%CI: 0.75, 0.78). Current breastfeeding was associated with 20% higher blood Pb levels (95%CI: 9%, 33%). We explored the underlying mechanism using NHANES 1999-2002 data that had bone turnover marker data (bone alkaline phosphatase (BAP) and N-terminal telopeptides (NTX)). We observed 46% higher BAP (95%CI: 32, 61) and 50% higher NTX (95%CI: 17, 91) with current breastfeeding. Among those not currently breastfeeding, those with higher BAP levels (third vs. first tertile) had 19% higher blood Pb levels (95%CI: 6, 33); those with higher NTX levels (third vs. first tertile) had 13% higher blood Pb levels (95% CI:-2, 31). We yielded similar results among those who had given birth in the past year. These data suggest increased blood Pb levels with current breastfeeding from greater bone turnover and skeletal mobilization of Pb. Given the health benefits of breastfeeding, replication of our findings and investigation into factors that mitigate skeletal mobilization of Pb are warranted.