Glycemic Index, Glycemic Load and Depression: A Systematic Review and Meta-Analysis of Cross-Sectional Studies

Although several studies have investigated the association between dietary glycemic index (GI), glycemic load (GL) and depression, results are inconsistent. This systematic review and meta-analysis was performed to summarize earlier evidence on the association between dietary GI, GL and depression.
After searching PubMed/Medline, ISI Web of Knowledge, Scopus and Google Scholar, related articles published until July 2017 were identified. Two reviewers independently screened the output of the search to identify potentially eligible studies. Studies that fulfilled the following criteria were included in the current study: 1) All human studies that considered GI or GL as the exposure variable and depression as the main outcome variable or as one of the outcomes were included in the systematic review; 2) publications in which odds ratios (ORs), rate or risk ratios (RR) or hazard ratios (HR) were reported as effect size were included in the meta-analysis. Finally, 10 studies, including six cross-sectional studies, one cohort study and three clinical trials were considered for inclusion in the systematic review, and five cross-sectional studies (out of 10 studies included in the systematic review) were included in the meta-analysis. The quality of cross-sectional studies included in this meta-analysis was examined by the Newcastle-Ottawa Scale (NOS).
Sample sizes of the included studies ranged from 40 to 87618 participants, and in total, 171508 participants aged ≥18 years were included in five studies. Combining seven effect sizes from five cross-sectional studies, no significant association was observed between dietary GI and odds of depression (summary effect size: 0.99; 95% CI: 0.78, 1.27). We also failed to find any significant association between dietary GL and risk of depression (summary effect size: 0.89; 95% CI: 0.75, 1.05).
By summarizing earlier findings, we found no significant association between dietary GI and GL and odds of depression. Further studies are required to reach a definitive conclusion.