GradedHealth

Does calcium protect your bones, and is it safe for your heart?

Calcium gives bones a small density boost, but large trials find little effect on fractures. Some analyses also link supplements to more heart attacks.

Published October 2026

Short answer

Calcium gives bones a small density boost, but trials show little fracture benefit alone, and supplements may raise heart attack risk. Evidence grade B (Moderate). Several meta-analyses of randomised trials; downgraded once for inconsistent fracture results and because bone density is a surrogate marker.

Key takeaways

  • Calcium from food or supplements raised bone density by about 0.6% to 1.8%, depending on the site and study length [1].
  • Calcium alone did not clearly reduce fractures across 11 trials of about 9,000 people [2].
  • Calcium plus vitamin D was linked to about 9% fewer fractures in one 2026 analysis, but earlier reviews disagree [2][3][4].
  • Calcium supplements were linked to about 24% to 31% more heart attacks in trial meta-analyses [5][6].

The short version

Calcium helps bones a little. Trials of calcium show small gains in bone density, but large reviews find little clear effect on breaking bones. Some analyses also link calcium supplements to a modestly higher risk of heart attacks, so it is worth discussing supplements with a doctor, especially if you have heart disease [1][2][5].

What the studies show

For bone density, the strongest evidence is a 2015 meta-analysis of 59 randomised trials. Calcium from food or from supplements raised bone density by about 0.6% to 1.8%, depending on the bone site and how long people took it [1]. The authors called these gains small and said they were unlikely to lead to a clinically significant drop in fracture risk [1].

For fractures, a 2026 BMJ review pooled 69 trials with about 154,000 people. Calcium alone showed little to no clear change in fractures across 11 trials of 9,067 people (risk ratio 0.91, 95% confidence interval 0.81 to 1.01) [2]. Calcium with vitamin D was linked to a small reduction (risk ratio 0.91, 0.84 to 0.99), while vitamin D alone made no clear difference [2].

Earlier reviews point the other way for combined products. A 2016 analysis of calcium plus vitamin D trials reported 15% fewer total fractures and 30% fewer hip fractures [3]. A 2017 analysis of older adults found no significant link between calcium and hip fracture [4].

For the heart, a 2010 BMJ meta-analysis of placebo-controlled trials found heart attacks were 31% more common in people taking calcium in the patient-level data (hazard ratio 1.31, 95% confidence interval 1.02 to 1.67) [5]. Stroke was not significantly raised in that analysis [5]. A 2011 analysis that added Women's Health Initiative data found a similar pattern, with heart attacks about 24% higher (relative risk 1.24, 1.07 to 1.45) [6].

The nuances

Most of the trials did not set heart events as their main outcome. The authors of one review argued this adds noise to the results but does not bias them toward harm [7]. Even so, the heart signal comes from secondary outcomes, so it is a warning sign rather than proof.

The review that reported the heart signal also suggested that food sources of calcium may be preferable, because they have not been linked to the same heart effects [7]. Food sources raised bone density in a similar way to supplements, except at the forearm [1].

For kidney health, calcium did not significantly raise the risk of kidney stones in a review of 10 studies of people with osteoporosis. The studies were small and of moderate quality [8]. Trials in people with kidney impairment suggest calcium supplements may raise cardiovascular risk [7].

In pregnancy, high-dose calcium (at least 1 g a day) reduced pre-eclampsia in trials, but the evidence was low quality. The same review found a rise in HELLP syndrome, a serious pregnancy complication, though the numbers were small [9].

What this means for you

Calcium from food helped bone density in trials about as well as supplements did [1]. If you are thinking about a supplement, especially to protect your bones, talk with a doctor about the heart findings and about your diet. People with heart disease or kidney problems should check with their doctor first [5][7]. For how calcium interacts with other medicines, see the calcium topic page.

Go deeper

  • Calcium — Calcium from food or supplements gives bones a small density boost, but large recent trials show little clear effect on fractures when calcium is taken alone.

References

  1. Calcium intake and bone mineral density: systematic review and meta-analysis.. BMJ, 2015.
  2. Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis.. BMJ, 2026.
  3. Calcium plus vitamin D supplementation and risk of fractures: an updated meta-analysis from the National Osteoporosis Foundation.. Osteoporos Int, 2016.
  4. Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis.. JAMA, 2017.
  5. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis.. BMJ, 2010.
  6. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis.. BMJ, 2011.
  7. Cardiovascular effects of calcium supplementation.. Osteoporos Int, 2011.
  8. Calcium supplementation and kidney stone risk in osteoporosis: a systematic literature review.. Clin Exp Rheumatol, 2012.
  9. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems.. Cochrane Database Syst Rev, 2018.