Assessing the efficacy and external validity of interventions promoting calcium or dairy intake in young adults: A systematic review with meta-analysis

Calcium and dairy products have a role in the prevention of chronic diseases and attainment of peak bone mass, during adolescence to young adulthood. However, intakes are often suboptimal and interventions to improve consumption of food sources are needed. This systematic review aimed to investigate the efficacy and external validity of interventions promoting calcium or dairy foods among young adults. Eight databases were searched from inception to identify relevant studies. Inclusion criteria included those aged 18 to 35 years in an intervention promoting calcium or dairy food intake. The mean age of the participants was 19.9 ± 1.4 years. Of the 16 studies that met the selection criteria, five studies were included in the meta-analyses for calcium (pooled effect size 0.35, 95% CI 0.04 to 0.67) and three studies for dairy (pooled effect size 0.31, 95% CI 0.11 to 0.50). The quality of the body of evidence was determined using the GRADE system, and was of overall low quality with high risk of bias. Our review suggests young adults respond favorably to interventions but the effect size is small.