The effect of calcium supplementation on bone density during lactation and after weaning

source extracted confidence: high 2026-04-09
#adult #bone-density #bone-regeneration #bone-resorption #calcium-carbonate

The effect of calcium supplementation on bone density during lactation and after weaning

Kalkwarf et al., 1997 | N Engl J Med | Rct

Citation

Kalkwarf H J, Specker B L, ... Ho M. The effect of calcium supplementation on bone density during lactation and after weaning. N Engl J Med. 1997-Aug-21;337(8):523-8

Abstract

BACKGROUND: Women may lose bone during lactation because of calcium lost in breast milk. We studied whether calcium supplementation prevents bone loss during lactation or augments bone gain after weaning. METHODS: We conducted two randomized, placebo-controlled trials of calcium supplementation (1 g per day) in postpartum women. In one trial (the study of lactation), 97 lactating and 99 nonlactating women were enrolled a mean (+/-SD) of 16+/-2 days post partum. In the second trial (the study of weaning), 95 lactating women who weaned their infants in the 2 months after enrollment and 92 nonlactating women were enrolled 5.6+/-0.8 months post partum. The bone density of the total body, lumbar spine, and forearm was measured at enrollment and after three and six months. RESULTS: The bone density of the lumbar spine decreased by 4.2 percent in the lactating women receiving calcium and by 4.9 percent in those receiving placebo and increased by 2.2 and 0.4 percent, respectively, in the nonlactating women (P<0.001 for the effect of lactation; P= 0.01 for the effect of calcium). After weaning, the bone density of the lumbar spine increased by 5.9 percent in the lactating women receiving calcium and by 4.4 percent in those receiving placebo; it increased by 2.5 and 1.6 percent, respectively, in the nonlactating women (P<0.001 for the effects of lactation and calcium). There was no effect of either lactation or calcium supplementation on bone density in the forearm, and there was no effect of calcium supplementation on the calcium concentration in breast milk. CONCLUSIONS: Calcium supplementation does not prevent bone loss during lactation and only slightly enhances the gain in bone density after weaning.

Key Findings

The bone density of the lumbar spine decreased by 4.2 percent in the lactating women receiving calcium and by 4.9 percent in those receiving placebo and increased by 2.2 and 0.4 percent, respectively, in the nonlactating women (P<0.001 for the effect of lactation; P= 0.01 for the effect of calcium). After weaning, the bone density of the lumbar spine increased by 5.9 percent in the lactating women receiving calcium and by 4.4 percent in those receiving placebo; it increased by 2.5 and 1.6 percen

Outcomes Measured

  • Requires manual extraction

Population

Field Value
Population See abstract
Sample Size 5
Age Range See abstract
Condition See abstract

MeSH Terms

  • Adult
  • Bone Density
  • Bone Regeneration
  • Bone Resorption
  • Calcium Carbonate
  • Calcium, Dietary
  • Double-Blind Method
  • Female
  • Humans
  • Lactation
  • Lumbar Vertebrae
  • Postpartum Period
  • Radius
  • Weaning

Evidence Classification

  • Level: Rct
  • Publication Types: Clinical Trial, Journal Article, Randomized Controlled Trial, Research Support, U.S. Gov't, P.H.S.
  • Vertical: calcium-bone

Provenance

  • PMID: 9262495
  • DOI: (not available)
  • PMCID: Not in PMC
  • Verified: 2026-04-09 via PubMed E-utilities API

Source extracted via PubMed E-utilities API on 2026-04-09