Calcium and Bone Health: What Trials Found for Bone Density, Osteoporosis and Fractures
What trials and reviews found when calcium was given to prevent fractures or raise bone density, with the populations, amounts and what the USPSTF concluded.
Content last updated . This page has not been medically reviewed.
Quick answer
Calcium is needed to build and keep bones, and a long-term lack of it can contribute to osteoporosis. [1] But "you need calcium" and "extra calcium pills prevent fractures" are different claims. The largest recent review of trials, in the BMJ in 2026, found little to no benefit of calcium alone, vitamin D alone or the two together on fractures and falls in mostly community-dwelling adults not at high risk. [2] Earlier reviews and the USPSTF reached similar or more cautious conclusions, as the table shows.
How the sources define the terms
- Osteoporosis: MedlinePlus describes it as a disease that makes bones weaker and more likely to break. [1]
- Bone density: measured with a bone density (DEXA) scan, which shows the mineral content of bone. A blood calcium test does not show it. [3]
- Fracture is the outcome that matters to patients. Higher bone density is a marker, not the same as fewer broken bones.
What trials and reviews found
| Question | What the source found | Strength of evidence |
|---|---|---|
| Calcium alone, any fracture | 2026 BMJ review of 69 trials (153,902 adults; 87% community-dwelling, 73% not at high risk). Calcium alone: 11 trials, 9,067 participants, risk ratio 0.91 (95% CI 0.81 to 1.01), moderate certainty. [2] | Mixed; no clear benefit |
| Calcium plus vitamin D, any fracture | Same review: 15 trials, 51,126 participants, risk ratio 0.91 (0.84 to 0.99), high certainty. The authors concluded little to no clinically meaningful benefit. [2] | Mixed |
| Calcium plus vitamin D, earlier review | 2019 review: 6 trials, 49,282 participants, daily calcium 1,000-1,200 mg plus vitamin D 400-800 IU, 6% lower risk of any fracture and 16% lower risk of hip fracture. [4] | Mixed; the 2026 review judged the absolute benefit small |
| One large trial, calcium plus vitamin D3 | Women's Health Initiative: 36,282 postmenopausal women aged 50-79, 1,000 mg elemental calcium as carbonate plus 400 IU vitamin D3 daily versus placebo, about 7 years. Hip bone density was 1.06% higher; hip fracture hazard ratio 0.88 (0.72 to 1.08); kidney stones rose (1.17). [5] | Hip fracture result not statistically significant |
| Calcium from food versus pills, fractures | 2015 BMJ review of trials and cohort studies in people over 50: dietary calcium was not associated with fracture, and evidence that calcium supplements prevent fractures was weak and inconsistent. [6] | Insufficient to weak |
| Bone density | 2015 BMJ review of 59 trials in people over 50: dietary calcium and supplements raised bone density by small amounts (about 0.6-1.8% at various sites), judged unlikely to cut fracture risk meaningfully. [7] | Biomarker only |
Biomarker change (bone density) is not a clinical outcome (fracture). Trials in postmenopausal women, in people already in care homes or with low calcium intake do not transfer automatically to everyone else.
What a US task force concluded
In 2018 the US Preventive Services Task Force looked at community-dwelling adults without osteoporosis, vitamin D deficiency or a previous fracture. It recommended against daily supplements of 400 IU or less of vitamin D and 1,000 mg or less of calcium for the primary prevention of fractures in postmenopausal women. It found the evidence insufficient for higher amounts, and for men and premenopausal women. It also found adequate evidence that vitamin D plus calcium increases kidney stones. [8] These findings do not apply to people with a history of osteoporotic fractures, increased risk of falls, osteoporosis or vitamin D deficiency. [8]Frequently asked questions
Does calcium prevent osteoporosis?
A lack of calcium over the long term can contribute to osteoporosis. [12] But a 2026 review found little to no effect of calcium supplements on fractures in mostly low-risk adults. [2]
Do calcium and vitamin D together reduce hip fractures?
A 2019 review of six trials reported 16% fewer hip fractures. [4] The Women's Health Initiative trial did not find a statistically significant reduction (hazard ratio 0.88, 0.72 to 1.08). [5]
Does the US task force recommend calcium for bones?
In 2018 it recommended against 1,000 mg or less of calcium with 400 IU or less of vitamin D daily for healthy postmenopausal women to prevent fractures. It did not apply this to people with osteoporosis or fracture history. [8]
Is calcium from food better for bones than pills?
In a 2015 review, dietary and supplement calcium raised bone density by similar small amounts. [7] Neither was shown to cut fractures meaningfully. [7]
Does a bone density scan measure calcium in my diet?
No. A blood calcium test does not show bone calcium, and a bone density scan measures the mineral content of bone. [3]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
People with osteoporosis or high fracture risk
Proper evidence not found for a separate verdict on calcium alone in people already taking osteoporosis medicines (we searched PubMed and read the reviews cited here): the 2026 review excluded adults receiving drug treatment for osteoporosis, and said evidence was limited for high-risk people and those in residential care. [2] The 2015 fracture review noted one trial in frail older women in residential care with low calcium and vitamin D that showed fewer fractures. [6] That is one trial in a specific group. MedlinePlus lists enough calcium, vitamin D and protein in a healthy diet as part of osteoporosis care alongside exercise, falls prevention and medicines. [9] The NHS suggests adults can usually get 700 mg a day from food. [10]
Limits and uncertainty
- The 2015 bone density review found similar increases in trials of calcium alone and of calcium with vitamin D. [7]
- The 2015 review found signs of bias favoring supplements in the published data. [6]
- Nothing here measures how much of your own diet is short of calcium. If your intake is very low, the trials above may not describe you.
Safety and who should ask a clinician
- Calcium supplements may cause gas, bloating and constipation in some people. [1]
- Supplements and kidney stones, and possible heart effects: see Calcium supplements, heart disease and kidney stones.
- Medicines: the NHS says alendronic acid should not be taken with milk and must be taken with tap water. [11] Ask a pharmacist about timing: Spacing supplements and medicines.
- Kidney disease, pregnancy and children: see Minerals and kidney disease and Pregnancy and breastfeeding.
- Tell the surgical team about supplements: Supplements before surgery.
- Talk to a clinician or pharmacist before starting a supplement. [1]
For bone care beyond calcium read Osteoporosis and bone health, and for amounts see Calcium intake levels.
References
- MedlinePlus, Calcium. Read 2026-10-22.
- Massé O et al. BMJ 2026;393:e088050. Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis. Read 2026-10-22.
- MedlinePlus, Calcium Blood Test. Read 2026-10-22.
- Yao P et al. JAMA Netw Open 2019;2(12):e1917789. Vitamin D and calcium for the prevention of fracture: a systematic review and meta-analysis. Read 2026-10-22.
- Jackson RD et al. N Engl J Med 2006;354(7):669-683. Calcium plus vitamin D supplementation and the risk of fractures. Read 2026-10-22.
- Bolland MJ et al. BMJ 2015;351:h4580. Calcium intake and risk of fracture: systematic review. Read 2026-10-22.
- Tai V et al. BMJ 2015;351:h4183. Calcium intake and bone mineral density: systematic review and meta-analysis. Read 2026-10-22.
- US Preventive Services Task Force. JAMA 2018;319(15):1592-1599. Vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling adults. Read 2026-10-22.
- MedlinePlus, Osteoporosis. Read 2026-10-22.
- NHS, Osteoporosis: prevention (page last reviewed 13 October 2022). Read 2026-10-22.
- NHS, Alendronic acid: how and when to take it. Read 2026-10-22.
- NHS, Calcium (page last reviewed 3 August 2020). Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.