An umbrella review of 22 meta-analyses, covering 69 unique primary studies and 286,584 adults, found that calcium supplementation, with or without vitamin D, produced small but statistically significant gains in bone mineral density at the total body, hip, lumbar spine and femoral neck. Risk fell for total, vertebral and non-vertebral fractures, but not for hip or wrist fractures. GRADE certainty was moderate for vertebral and non-vertebral fractures and low or very low elsewhere; heterogeneity was substantial.
The missing hip-fracture signal matters most, because hip fractures drive the largest share of disability, institutionalization and mortality in older adults. Small density gains of a percent or two do not necessarily translate into the outcomes people care about, and earlier work, including the Women's Health Initiative and prior meta-analyses, has been inconsistent here. An umbrella review also inherits the flaws of its sources: overlapping trials, mixed doses, mixed baseline calcium intakes and bundled vitamin D arms make it impossible to isolate calcium's own effect. Cardiovascular and kidney-stone concerns raised by earlier trials are outside this review's scope, so the safety side of the ledger stays open.
Practically, the findings support food-first calcium intake, roughly 1,000 to 1,200 mg daily from diet and supplements combined, with supplements reserved for people who fall short, rather than routine high-dose pills. Resistance training, adequate protein and vitamin D status likely matter at least as much. This is confirmatory and incremental: it reinforces a modest benefit, and the authors rightly call for long-term, high-quality trials.