Summary of findings 3. Calcium and vitamin D compared to placebo for increasing bone mineral density in premenopausal women.
| Calcium and vitamin D compared to placebo for increasing bone mineral density in premenopausal women | |||||||
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Patient or population: premenopausal women (ages 18–36 years)
Setting: community
Intervention: calcium and vitamin D
Comparison: placebo Dosage: vitamin D 10 μg (400 IU) + calcium 600 mg (1 tablet a day); vitamin D3 5 μg (200 IU) + calcium 1000 mg (2 sachets per day) | |||||||
| Outcomes | Relative effect (95% CI) | Anticipated absolute effects* (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | What happens | ||
| Without calcium + vitamin D | With calcium + vitamin D | Difference | |||||
| Total hip BMD assessed with: DXA (g/cm2) Follow‐up: median 12 months | — | — | — | MD 0.03 g/cm2 lower (0.06 lower to 0) | 408 (1 RCT) | ⊕⊕⊕⊝ Moderatea | Calcium and vitamin D combined supplementation does not increase total hip BMD mean difference in healthy premenopausal woman.b |
| Lumbar spine BMD assessed with: DXA (g/cm2) Follow‐up: median 12 months | — | — | — | MD 0.01 g/cm2 higher (0.01 lower to 0.03 higher) | 76 (1 RCT) | ⊕⊕⊕⊝ Moderatea | Calcium and vitamin D combined supplementation does not increase BMD mean difference in the lumbar spine in healthy premenopausal woman.b |
| Quality of life | — | — | — | — | — | — | Not reported. |
| Vertebral fracture | — | — | — | — | — | — | Not reported. |
| Non‐vertebral fracture | — | — | — | — | — | — | Not reported. |
| Withdrawals from the study for any reason Follow‐up: median 12 months | RR 0.82 (0.29 to 2.35) | 10.0% | 8.2% (2.9% to 23.5%) | 1.8% lower (7.1% lower to 13.5% higher) | 541 (2 RCTs) | ⊕⊕⊝⊝ Lowc,d | Calcium plus vitamin D supplementation may not reduce or increase withdrawals for any reason. |
| Serious adverse events | — | — | — | — | — | — | Not reported. |
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BMD: bone mineral density; CI: confidence interval; DXA: dual‐energy X‐ray absorptiometry; RCT: randomised controlled trial; RR: risk ratio. | |||||||
| GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect. | |||||||
aDowngraded one level for the studies analysed that carried large weight for the overall effect estimate rated as unclear risk of bias in more than two domains. bOutcome included in only one study. cDowngraded one level, the CIs included both increased and decreased withdrawals. dDowngraded one level for inconsistency due to the studies reporting different outcomes measured (BMD mean difference of total hip and BMD in the lumbar spine), a difference that was supported by non‐overlapping CIs, I2 greater than 70%, and substantial heterogeneity of effect estimates.