Influence of maternal bone lead burden and calcium intake on levels of lead in breast milk over the course of lactation

Department of Environmental Health, Harvard School of Public Health, Boston, MA 02215, USA.
American Journal of Epidemiology (Impact Factor: 5.23). 02/2006; 163(1):48-56. DOI: 10.1093/aje/kwj010
Source: PubMed


The authors studied 367 women who were breastfeeding their infants in Mexico City, Mexico, between 1994 and 1995 to evaluate the effect of cumulative lead exposure, breastfeeding practices, and calcium intake on breast milk lead levels over the course of lactation. Maternal blood and breast milk lead levels were measured at 1, 4, and 7 months postpartum. Bone lead measurements were obtained at 1 month postpartum. At 1, 4, and 7 months postpartum, respectively, the mean breast milk lead levels were 1.4 (standard deviation (SD), 1.1), 1.2 (SD, 1.0), and 0.9 (SD, 0.8) microg/liter and showed a significant decreasing trend over the course of lactation (p < 0.00001). The relations of bone lead and blood lead to breast milk lead were modified by breastfeeding practice, with the highest breast milk lead levels among women with a high level of patella lead who were exclusively breastfeeding. Dietary calcium supplementation increased the rate of decline in breast milk lead by 5-10%, in comparison with a placebo, over the course of lactation, suggesting that calcium supplementation may constitute an important intervention strategy, albeit with a modest effect, for reducing lead in breast milk and thus the potential for exposure by infants.

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Available from: Chitra Amarasiriwardena, Oct 06, 2015
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    • "A study performed on a group of mothernewborn pairs showed a strong correlation between the BLLs in the mothers and their newborns; in particular, the blood lead concentration of infants was approximately 90 % of that of the mothers (Amitai et al. 1999). Furthermore, Pb accumulated in the mother's bones from past environmental exposures can be excreted into breast milk, and despite the low levels excreted, it may strongly influence the infant's BLLs (Ettinger et al. 2006). The nervous system of the fetus is especially susceptible to Pb, which may penetrate the incomplete bloodbrain barrier. "
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    • "Moreover, exposure can occur in work environments24 and through the transfer of lead from mother to fetus,25–27 which occurs with a placental transmission ratio of 0.6. The transfer of lead from mothers to nursing infants through breast milk occurs in much lower amounts by comparison, with the mammary gland being a barrier that effectively maintains a low milk:plasma ratio for lead.25–27 Despite a documented wide range of lead concentrations in human milk, there have been no reports of toxicity caused by breast feeding.25 "
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    • "In a randomized, double-blind, placebocontrolled trial of 1,200 mg daily calcium supplementation in lactating women, we have previously shown that calcium supplementation reduced maternal blood lead by 15–20% (Hernández-Avila et al. 2003) and breast milk lead by 5–10% (Ettinger et al. 2006) over the course of lactation. Our objective in the present study was to evaluate the effect of 1,200 mg daily calcium supplementation on maternal blood lead levels during pregnancy, the period of greater relevance for maternal–fetal transfer of lead. "
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    ABSTRACT: Prenatal lead exposure is associated with deficits in fetal growth and neurodevelopment. Calcium supplementation may attenuate fetal exposure by inhibiting mobilization of maternal bone lead and/or intestinal absorption of ingested lead. Our goal was to evaluate the effect of 1,200 mg dietary calcium supplementation on maternal blood lead levels during pregnancy. In a double-blind, randomized, placebo-controlled trial conducted from 2001 through 2003 in Mexico City, we randomly assigned 670 women in their first trimester of pregnancy to ingest calcium (n = 334) or placebo (n = 336). We followed subjects through pregnancy and evaluated the effect of supplementation on maternal blood lead, using an intent-to-treat analysis by a mixed-effects regression model with random intercept, in 557 participants (83%) who completed follow-up. We then conducted as-treated analyses using similar models stratified by treatment compliance. Adjusting for baseline lead level, age, trimester of pregnancy, and dietary energy and calcium intake, calcium was associated with an average 11% reduction (0.4 microg/dL) in blood lead level relative to placebo (p = 0.004). This reduction was more evident in the second trimester (-14%, p < 0.001) than in the third (-8%, p = 0.107) and was strongest in women who were most compliant (those who consumed > or = 75% calcium pills; -24%, p < 0.001), had baseline blood lead > 5 microg/dL (-17%, p < 0.01), or reported use of lead-glazed ceramics and high bone lead (-31%, p < 0.01). Calcium supplementation was associated with modest reductions in blood lead when administered during pregnancy and may constitute an important secondary prevention effort to reduce circulating maternal lead and, consequently, fetal exposure.
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