Effects of Walnut Consumption on Endothelial Function in Type 2 Diabetic Subjects

A randomized controlled crossover trial

  1. Yingying Ma, MD, RVT,
  2. Valentine Yanchou Njike, MD, MPH,
  3. John Millet, BA,
  4. Suparna Dutta, MD, MPH,
  5. Kim Doughty, BS,
  6. Judith A. Treu, MS, RD and
  7. David L. Katz, MD, MPH
  1. Prevention Research Center, Yale University School of Medicine, Derby, Connecticut.
  1. Corresponding author: David L. Katz, katzdl{at}


OBJECTIVE To determine the effects of daily walnut consumption on endothelial function, cardiovascular biomarkers, and anthropometric measures in type 2 diabetic individuals.

RESEARCH DESIGN AND METHODS This study was a randomized, controlled, single-blind, crossover trial. Twenty-four participants with type 2 diabetes (mean age 58 years; 14 women and 10 men) were randomly assigned to one of the two possible sequence permutations to receive an ad libitum diet enriched with 56 g (366 kcal) walnuts/day and an ad libitum diet without walnuts for 8 weeks. Subjects underwent endothelial function testing (measured as flow-mediated dilatation [FMD]) and assessment of cardiovascular biomarkers before and after each 8-week treatment phase. The primary outcome measure was the change in FMD after 8 weeks. Secondary outcome measures included changes in plasma lipids, A1C, fasting glucose, insulin sensitivity, and anthropometric measures.

RESULTS Endothelial function significantly improved after consumption of a walnut-enriched ad libitum diet compared with that after consumption of an ad libitum diet without walnuts (2.2 ± 1.7 vs. 1.2 ± 1.6%; P = 0.04). The walnut-enriched diet increased fasting serum glucose and lowered serum total cholesterol and LDL cholesterol from baseline (10.0 ± 20.5 mg/dl, P = 0.04; −9.7 ± 14.5 mg/dl, P < 0.01; and −7.7 ± 10 mg/dl, P < 0.01, respectively), although these changes were not significant compared with those for an ad libitum diet without walnuts. There were no significant changes in anthropometric measures, plasma A1C, and insulin sensitivity.

CONCLUSIONS A walnut-enriched ad libitum diet improves endothelium-dependent vasodilatation in type 2 diabetic individuals, suggesting a potential reduction in overall cardiac risk.


  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Received July 23, 2009.
    • Accepted October 20, 2009.
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  1. Diabetes Care vol. 33 no. 2 227-232
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