Glycemic index, glycemic load, and depression: a systematic review and meta-analysis.

BACKGROUND/OBJECTIVES: 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.

SUBJECTS/METHODS: We searched in PubMed/Medline, ISI Web of Knowledge, Scopus, EMBASE, and Google Scholar to identify related articles published until April 2018. Publications that fulfilled the following criteria were included in the current study: (1) publications with participants aged ≥ 18 years; (2) studies that considered GI or GL as the exposure; (3) studies that considered depression as the main outcome or as one of the outcomes; and (4) publications in which odds ratios (ORs) or mean difference were reported as the effect size. Finally, 11 studies, including 6 cross-sectional studies, 2 cohort studies, and 3 clinical trials were considered for inclusion in the systematic review, and 5 cross-sectional studies, 2 cohort studies, and 2 clinical trials (out of 11 studies included in the systematic review) were included in the meta-analysis. The quality of cross-sectional and cohort studies examined by the Newcastle-Ottawa Scale (NOS) and the quality of clinical trials examined using Cochrane Collaboration Risk of Bias tool. We also assessed the quality of evidence with the GRADE system.

RESULTS: Sample sizes of the included cross-sectional studies ranged from 140 to 87,618 participants, and in total 101,389 participants were included in 6 studies. In total, 85,500 participants were included in 2 cohort studies. Sample sizes of the included clinical trials ranged from 40 to 82 participants, and in total 164 participants were included in three studies. Combining seven effect sizes from five cross-sectional studies, no significant association was observed between dietary GI and odds of depression (OR: 1.01; 95% CI: 0.94, 1.08; I2  = 80.2%; n = 5). We also failed to find any significant association between dietary GL and odds of depression (OR: 0.93; 95% CI: 0.84, 1.04; I2  = 42%; n = 5). Combining two effects sizes from two cohort studies, there was a significant positive association between dietary GI and depression (HR: 1.13; 95% CI: 1.02, 1.25; I2  = 86.1%, n = 2). In addition, combining two effect sizes from two clinical trials, we found a significant change in depression score after consumption of a high-GL diet (weighted mean difference (WMD): 0.66; 95% CI: 0.28, 1.04; I2  = 0.0%, n = 2).

CONCLUSIONS: Summarizing earlier findings, we found no significant association between either dietary GI or GL and odds of depression in cross-sectional studies. However, a significant positive association was observed between dietary GI and depression in cohort studies. In addition, a significant effect of a high-GL diet consumption on risk of depression was seen in clinical trials.