Effects of dietary restriction on cognitive function: a systematic review and meta-analysis

Background Potential positive link between cognitive function and dietary restriction has been widely concerned. The present study describes a systematic review and preliminary meta-analysis to assess the efficacy of dietary restriction on cognitive function. We classified dietary restrictions as Calories Restriction (CR) and Intermittent Fasting (IF). Method This systematic review and meta-analysis conducted following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Statement (PRISMA) Checklist, Databases including PubMed, Embase, Web of Science, and the Cochrane Library were searched for randomized controlled trials (RCTs) assessing the cognition effectiveness of dietary restriction from database inception to Sep 2021. Result Eleven RCTs met the inclusion criteria in the systematic review and meta-analysis. The overall effect of dietary restriction on cognitive function is SMD = 0.22 (95% CI: 0.09-0.34, p < 0.01). The effect on global function SMD = 0.35 (95% CI: 0.04-0.65, p < 0.05) and memory SMD = 0.18 (95% CI: 0.00-0.35, p = 0.05) is significant. MCI showed the best effectiveness SMD = 0.36 (95% CI: 0.05-0.68, p < 0.05), followed by the normal weight population SMD = 0.28 (95% CI: 0.03-0.52, p < 0.05) and overweight population SMD = 0.20 (95% CI: 0.06-0.34, p < 0.01). No statistically significant difference showed between IF and CR (p > 0.05). Conclusion Our study demonstrated that dietary restriction has varying degrees of positive effect on cognitive function in overweight/normal-weight people and MCI. However, it should be cautious when generalizing to other populations. Additional high-quality, large-scale, cohort and intervention studies are needed to further assess the effectiveness of dietary restriction on cognition.