Background: Environmental exposures, such as inadequate diet may be considered as risk factors of childhood fractures. When building optimal bone mass, the bone homeostasis is closely regulated by calcium absorption and reabsorption, making calcium essential for bone mineral accrual especially during growth. A systematic review and meta-analysis was conducted to examine the association between calcium intake and childhood fractures.
Method: Studies published up until January 2014 were identified based on literature search in the MEDLINE, Web of Science and SCOPUS databases and hand searching in references by first author based on predefined inclusion criteria (study design, age 2-13 years, health status). Meta-analysis was done for case-control studies examining differences in mean calcium intake in the case compared with the control group. Random effect analysis was performed based on the effect-estimates derived as the differences in mean calcium intakes between the cases and controls. The corresponding standard errors were derived based on the standard formula related to differences in means through usage of the Ns and standard deviations.
Results: In total, twelve studies examined overall calcium intake, of which nine were case-control studies, one was performed with a case-cohort design and two were longitudinal studies. The literature identified in the systematic review, suggests that there may be a threshold effect for intakes of calcium below RDA or perhaps even a u-shaped association including the risk of fractures at both low and high intake levels, due to the contradictive results from studies examining mean calcium intake. The pooled effect size of the nine case-control studies, which had appropriate data for the meta-analysis showed no association (p=0.99) with fair heterogeneity (I2=69.3%, p=0.001) using the random-effects model.
Conclusion: Dietary calcium intake was not consistently associated with reduced incidence of childhood fractures in neither the systematic review, nor the pooled results from the meta-analysis.
Disclosure: The authors declared no competing interests. Funded by the Danish Council for Strategic Research (11-116213) and the University of Southern Denmark.