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

  • 2025-02-03
  • Journal of diabetes and metabolic disorders 24(1)
    • Amir Hadi
    • Mohammad Zeinali Khosroshahi
    • Ahmed Hussein Zwamel
    • Omid Asbaghi
    • Fatemeh Naeini
    • Mayam Miraghajani
    • Mehran Nouri
    • Ehsan Ghaedi

Study Design

Type
Review
Methods
Systematic review and meta-analysis of RCTs, searched PubMed, Scopus, Web of Science, Cochrane up to February 2023, random effects models
Funding
Unclear

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, P = 0.04), and body weight (WMD = -0.14 kg; 95% CI: -0.24, -0.04; P = 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; P = 0.34), insulin levels (WMD = 1.27 mIU/ml; 95% CI: -0.59, 3.14; P = 0.18), HbA1C (WMD = 0.00%; 95% CI: -0.09, 0.10; P = 0.95), and BMI (WMD = -0.10 kg/m2; 95% CI: -0.40, 0.20; P = 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.

Research Insights

  • Walnut→Reduced Body Mass Index

    BMI (WMD = -0.10 kg/m2; 95% CI: -0.40, 0.20; P = 0.50)

    Effect
    Neutral
    Effect size
    Small
  • Walnut→Reduced Body Weight

    body weight (WMD = -0.14 kg; 95% CI: -0.24, -0.04; P = 0.008)

    Effect
    Beneficial
    Effect size
    Small
  • Walnut→Reduced Fasting Blood Glucose Levels

    walnut supplementation did not have a significant effect on FBS (WMD = 0.62 mg/dL; 95% CI: -0.66, 1.91; P = 0.34)

    Effect
    Neutral
    Effect size
    Small
  • Walnut→Reduced HOMA-IR

    Walnut supplementation was found to significantly reduce HOMA-IR (WMD = -0.29; 95% CI: -0.57, -0.01, P = 0.04)

    Effect
    Beneficial
    Effect size
    Small
  • Walnut→Reduced Hemoglobin A1c

    HbA1C (WMD = 0.00%; 95% CI: -0.09, 0.10; P = 0.95)

    Effect
    Neutral
    Effect size
    Small
  • Walnut→Reduced Insulin Levels

    insulin levels (WMD = 1.27 mIU/ml; 95% CI: -0.59, 3.14; P = 0.18)

    Effect
    Neutral
    Effect size
    Small
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