Effect of calcium supplementation in pregnancy on maternal bone outcomes in women with a low calcium intake

Medical Research Council Keneba, Keneba, The Gambia.
American Journal of Clinical Nutrition (Impact Factor: 6.92). 08/2010; 92(2):450-7. DOI: 10.3945/ajcn.2010.29217
Source: PubMed

ABSTRACT Mobilization of maternal bone mineral partly supplies calcium for fetal and neonatal bone growth and development.
We investigated whether pregnant women with low calcium intakes may have a more extensive skeletal response postpartum that may compromise their short- or long-term bone health.
In a subset of participants (n = 125) in a double-blind, randomized, placebo-controlled trial (International Trial Registry: ISRCTN96502494) in pregnant women in The Gambia, West Africa, with low calcium intakes (approximately 350 mg Ca/d), we measured bone mineral status of the whole body, lumbar spine, and hip by using dual-energy X-ray absorptiometry and measured bone mineral status of the forearm by using single-photon absorptiometry at 2, 13, and 52 wk lactation. We collected blood and urine from the subjects at 20 wk gestation and at 13 wk postpartum. Participants received calcium carbonate (1500 mg Ca/d) or a matching placebo from 20 wk gestation to parturition; participants did not consume supplements during lactation.
Women who received the calcium supplement in pregnancy had significantly lower bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the hip throughout 12 mo lactation (mean +/- SE difference: BMC = -10.7 +/- 3.7%, P = 0.005; BA = -3.8 +/- 1.9%, P = 0.05; BMD = -6.9 +/- 2.6%, P = 0.01). The women also experienced greater decreases in bone mineral during lactation at the lumbar spine and distal radius and had biochemical changes consistent with greater bone mineral mobilization.
Calcium supplementation in pregnant women with low calcium intakes may disrupt metabolic adaptation and may not benefit maternal bone health. Further study is required to determine if such effects persist long term or elicit compensatory changes in bone structure.

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    • "Among healthy American women, studies utilizing dual-energy X-ray absorptiometry (DXA) indicate that extended lactation (6 months) is associated with BMD losses of about 5% at the lumbar spine, with restoration of BMD to pre-pregnancy values by 12 months post-partum (Sowers et al., 1993). In contrast, DXA studies of rural Gambian women, who have high fertility , closely spaced births, on-demand breastfeeding for approximately 2 years, and low calcium intake, indicate incomplete restoration of lumbar spine BMD to prepregnancy values by 12 months post-partum (Jarjou et al., 2010). Complete BMD restoration among Gambian women may occur later in lactation or after weaning (Sawo et al., 2013). "
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