Calcium supplementation does not improve bone density in lactating women

Supplementation with calcium confers no clinically significant benefits on bone mineral density (BMD) in lactating women, according to the results of a meta-analysis.

“However, there was adequate dietary intake before supplementation in some studies, and others did not measure baseline calcium intake,” the investigators noted.

Databases were searched electronically from inception to January 2020. Two investigators screened the studies, extracted data, and assessed the risk of bias of eligible studies. Random-effects models were used to pool percentage change in BMD, reported as weight mean differences (WMDs) with 95 percent confidence intervals (CIs). The Cochrane risk of bias toll was used to evaluate risk of bias.

Five randomized controlled trials including a total of 567 lactating women met the eligibility criteria, all of which showed a high risk of bias. Mean baseline calcium intake ranged from 562 to 1,333 mg/d.

Calcium supplementation (600/1,000 mg/d) did not show a significant effect on BMD at the lumbar spine (WMD, 0.74 percent, 95 percent CI, –0.10 to 1.59 percent; I2, 47 percent, 95 percent CI, 0–81 percent; n=527 from five trials) or the forearm (WMD, 0.53 percent, 95 percent CI, –0.35 to 1.42 percent; I2, 55 percent, 95 percent CI, 0–85 percent; n=415 from four trials) compared with placebo/no intervention.

BMD at other sites was examined in single trials. Calcium supplementation was shown to have a small-to-moderate impact on total hip BMD (WMD, 3.3 percent, 95 percent CI, 1.5–5.1 percent) but no effect on total body or femoral neck BMD.

“Advising lactating women to meet the current recommended calcium intakes (with supplementation if dietary intake is low) is warranted unless new high-certainty evidence to the contrary from robust clinical trials becomes available,” the investigators said, noting the need for more research in larger samples of women from diverse ethnic and racial groups.