Thirty four studies were included (n=6,815): 21 RCTs (n=3,821), 10 cross-sectional studies (n=2,486) and three cohort studies (n=508). The duration of follow-ups in the RCTs ranged from 12 to 48 months.
RCTs: Data from all RCTs showed that dietary calcium supplementation was associated with a non-statistically significant increase in total body/bone mineral content (mean difference (in grams) 2.05g, 95% CI (Confidence Interval): -3.26, 7.36, 12 RCTs). There was evidence of statistically significant heterogeneity (p<0.04). Dietary calcium supplementation was associated with a significantly higher bone mineral content among children with low base-line calcium intakes (mean difference 49.9 g, 95% CI: 24.0, 76.6, three RCTs).
There was no significant difference in lumbar spine bone mineral content between calcium/dairy supplement plus vitamin D groups and controls (mean difference 35 g, 95% CI: -6.8, 41.8, two RCTs). There was no evidence of statistical heterogeneity (p=0.47). There was no significant difference in lumbar spine bone mineral content between vitamin D groups and controls (mean difference 1.41 g, 95% CI: -0.3, 3.12, two RCTs).
Cross-sectional and cohort studies: Overall, data from these sources were limited in quantity and quality, so no meaningful interpretation was possible.