Commentary

The review by Vartanian et al adds to our knowledge of the negative effects of soft drink consumption on nutrition and health. Overall, this review of 88 randomised controlled trials, longitudinal, and cross-sectional studies was strong. The authors considered variables such as funding sources, and the results of the review are strengthened by greater associations found among those studies with more robust designs. Limitations of the review include failure to provide readers with a table of characteristics of the included studies and a description of how the quality of these studies was assessed. In addition, there remained significant heterogeneity in the effect sizes observed, despite performing meta-analysis by different design and moderating variables. The findings regarding nutrient intake and health outcomes are further limited by the small number of included studies. For example, the conclusion of an association between soft drink consumption and type 2 diabetes is based on a single, albeit large, cohort study.

Vartanian et al used effect size as a measure of association; the closer the effect size to 1.0 or −1.0, the larger the positive or negative association. The results indicate positive associations between soft drink consumption and energy intake and body weight and negative associations with milk and calcium intake. The recommendation by Vartanian et al for reduced soft drink consumption remains within the scope of their review and follows from the strongest finding of their review: the greater the soft drink consumption, the greater the food energy intake. Using clinical expertise, most practitioners would agree that the benefits of limiting soft drink consumption outweigh the risks. Thus, the review by Vartanian et al provides practitioners with evidence to recommend limiting soft drink consumption to their clients.