Impact of walnut consumption on glycemic control and anthropometric indices: a systematic review and meta-analysis of randomized controlled trials.

Objectives: Previous studies have led to conflicting results regarding the effect of walnut consumption on glycemic control, and anthropometric indices. This study aimed to evaluate the efficacy of walnut consumption on serum levels of fasting blood sugar (FBS), fasting insulin, hemoglobin A1C (HbA1c), homeostasis model assessment of insulin resistance (HOMA-IR), weight and body mass index (BMI) through a systematic review and meta-analysis of randomized controlled trials (RCTs).

Methods: PubMed, Scopus, Web of Science, and the Cochrane databases were searched up to February 2023. Weighted mean difference (WMD) was analyzed using random effects models to assess the overall effect.

Results: A total of thirty-two RCTs were included in the systematic review and meta-analysis. Walnut supplementation was found to significantly reduce HOMA-IR (WMD = -0.29; 95% CI: -0.57, -0.01,  = 0.04), and body weight (WMD = -0.14 kg; 95% CI: -0.24, -0.04;  = 0.008). However, the meta-analysis showed that walnut supplementation did not have a significant effect on FBS (WMD = 0.62 mg/dL; 95% CI: -0.66, 1.91;  = 0.34), insulin levels (WMD = 1.27 mIU/ml; 95% CI: -0.59, 3.14;  = 0.18), HbA1C (WMD = 0.00%; 95% CI: -0.09, 0.10;  = 0.95), and BMI (WMD = -0.10 kg/m; 95% CI: -0.40, 0.20;  = 0.50).

Conclusion: In conclusion, this study found a significant reduction in HOMA-IR levels and body weight with walnut supplementation, while other glycemic markers, and obesity-related indices did not change significantly. Future well-designed trials are needed to confirm these results.