Background: For patients > 50, 1000-1200 mg daily of calcium recommended to prevent fractures.
58 cohort studies of dietary calcium intake and fracture risk in >700K patients.
74% of studies reported no associated between dietary Ca intake and risk for total fx, hip fx, vertebral fx or forearm fx.
Positive associations in the remaining studies were weak.
26 RCTs, n = 69K, mostly women; Ca intake >1000mg daily in most studies:
– lowered risk for total fx (RR 0.89)
– vertebral fx (RR 0.86)
– but not hip or forearm fx
Probably publication bias in some trials.
Conclusion: Dietary Ca intake not associated with fx risk, and Ca supplements have minimal effects at best – and important to remember calcium supplements have known harms (adverse cardiovascular events, GI symptoms, nephrolithiasis).
BMJ 2015 Sept 29;351:h4580
Meta-analysis of 59 RCTs
– 15 trials of increased dietary Ca, n = 1500
– 51 trials of Ca supplementation, n = 12000
– nearly all women, age >50 at baseline
– underwent baseline and post-intervention BMD testing
Increasing dietary Ca to 250-3320mg QD increased BMD by 0.6-1.0% (hip, total) at one year and 0.7-1.8% (hip, total, femoral, L-spine) at 2 years.
Calcium supplements (250-2500mg QD) increased BMD at all five sites at 1 year with little additional change.
Increases in BMD were similar across all trial groups: dietary vs supplements, Ca vs Ca/vit D, doses <1000mg/d vs >1000mg/d, and baseline dietary intake <800/d vs >800/d.
Conclusion: Yes, there are small increases in BMD with increased dietary or supplement Ca, BMD is only a surrogate marker for fx risk, and this small increase may not translate to lower fracture risk. (See above summary). Clinicians should not routinely recommend Ca/vit D supplements simply to increase BMD.
BMJ 2015 Sep 29; 351:h4183