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Evidence-Based Supplement Research
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Calcium

What does the research say about Calcium?

2 health outcomes synthesised

Calcium is a mineral studied for 2 health outcomes, both supported by low-strength evidence. The strongest area of research involves bone density, where 2 of 3 studies in postmenopausal women reported small beneficial effects on total hip bone mineral density, though often in combination with exercise or collagen. For pregnancy outcomes, calcium at doses around 1000 mg/day showed a small, non-significant reduction in stillbirth in 1 of 3 meta-analyses.

Strongest evidence No outcomes reached moderate or high evidence strength. Both syntheses are rated low evidence, based on 3 studies each. The most consistent direction is for total hip bone mineral density, where 2 of 3 studies found a small benefit, but the highest-quality study was neutral.

Mixed or weaker evidence For stillbirth, the evidence is predominantly neutral: 2 of 3 meta-analyses found no significant effect, and none of the studies reached statistical significance. Effect sizes were small and confidence intervals crossed the null. Both outcomes suffer from small sample sizes and preliminary conclusions.

Effective dose patterns A consistent dose range emerges only for stillbirth, where studies used 1000 mg/day or higher (≥1000 mg/day) as calcium carbonate. For bone density, no independent effective dose was identified because benefits occurred only when calcium was combined with exercise or collagen.

Population insights Research focuses on two distinct populations: postmenopausal women for bone density and pregnant women for stillbirth. In bone density, the beneficial effects are context-dependent (seen only alongside other interventions), while stillbirth studies examine calcium alone or unspecified forms.

Notable caveats Both evidence bases are small (3 studies each) and considered preliminary. The only high-quality study for bone density found a neutral effect. Many confidence intervals are wide and include zero, indicating uncertainty. Calcium's independent contribution is unclear—bone density results may stem from exercise or collagen rather than calcium alone.

Frequently asked

  • What is Calcium good for according to research?
    Research on calcium focuses on two areas: bone density and pregnancy outcomes. For total hip bone mineral density in postmenopausal women, 2 of 3 studies reported small benefits, but only when combined with exercise or collagen. For stillbirth in pregnant women, 1 of 3 meta-analyses found a small reduction, while two found neutral effects.
  • What dose of Calcium is typically used in studies?
    In stillbirth research, doses around 1000 mg/day or higher (≥1000 mg/day) were used, often as calcium carbonate. For bone density, studies did not specify an independent effective dose because benefits appeared only when calcium was taken with exercise or collagen.
  • Who benefits most from Calcium?
    The populations studied are postmenopausal women for bone density and pregnant women for stillbirth. Benefits for bone density were seen in postmenopausal women, but only in combination with other interventions. For stillbirth, the evidence is too uncertain to identify a clear benefit group.
  • Are there caveats or limitations in the research on Calcium?
    Yes. Both syntheses are based on only 3 studies each, making conclusions preliminary. For bone density, the highest-quality study found a neutral effect, and beneficial studies had low quality scores. For stillbirth, all studies had wide confidence intervals crossing the null, meaning the effect may be smaller than suggested.
  • Does Calcium help with increased total hip bone mineral density?
    Two out of three studies reported a small beneficial effect, but these used calcium alongside exercise or collagen, not calcium alone. The only high-quality study (score 7) found a neutral effect, so it is unclear whether calcium independently contributes to bone density improvement.
  • Does Calcium reduce stillbirth?
    One of three meta-analyses found a small reduction in stillbirth with calcium supplementation, while two found neutral effects. None of the studies reached statistical significance, and the evidence is considered low strength with wide confidence intervals. The effect of calcium alone on stillbirth remains uncertain.

Most-studied combinations with Calcium

most supplement research is combination research
Also studied with:Potassium (2), Phosphorus (2), Zinc (3), Magnesium (3), Iron (2), Vitamin D (9)

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