The effects of garlic extract upon endothelial function, vascular inflammation, oxidative stress and insulin resistance in adults with type 2 diabetes at high cardiovascular risk. A pilot double blind randomized placebo controlled trial

J Diabetes Complications. May-Jun 2016;30(4):723-7. doi: 10.1016/j.jdiacomp.2016.01.003. Epub 2016 Jan 6.


Background and aims: Endothelial dysfunction, vascular inflammation and oxidative stress have been integrally linked to the pathogenesis of both type 2 diabetes and cardiovascular disease. Aged Garlic Extract (AGE), a potent antioxidant, has been shown in previous studies to attenuate these novel risk factors in a non-diabetic population.

Aims: This study tested the hypothesis that AGE may improve endothelial function, oxidative stress, vascular inflammation and insulin resistance in high risk cardiovascular subjects with type 2 diabetes.

Methods: A double blind, placebo controlled crossover pilot study was performed in 26 subjects with type 2 diabetes who received 1200 mg of AGE or placebo daily for 4 weeks with a 4 week washout period. Plasma HsCRP was measured as a marker of inflammation. Plasma TAOS, blood GSH/GSSG and plasma LHP were measured as markers of oxidative stress/anti-oxidant defense. Insulin resistance was measured using the HOMA-IR method. Endothelial function was measured using change in the reflective index (RI) post-salbutamol using digital photoplethysmography and urinary albumin/creatinine ratio was measured as a biochemical surrogate. Measurements were taken at baseline and after intervention with AGE or placebo.

Results: Of the 26 patients studied (male 17, female 9), age was 61 ± 8 years (mean ± 1 SD), HbA1c 7.2 ± 1.1%, BP 130/75 ± 15.9/9.8 mmHg, total cholesterol 4.2 ± 0.81 mmol/l, triglyceride 2.11 ± 1.51 mmol/l, and HDL cholesterol 1.04 ± 0.29 mmol/l. The majority of patients were being treated with metformin (59%), aspirin (50%) and statin (96%) therapy. 36% were treated with an ACEI. There were no changes in these therapies throughout the study. Treatment with AGE had no significant effect upon the above metabolic parameters including insulin resistance. Treatment with AGE also had no significant effect on markers of endothelial function (plethysmography), oxidative stress (TAOS, GSH/GSSG, LHP) or inflammation (HsCRP).

Conclusion: In this group of type 2 diabetic patients at high cardiovascular risk, 4 weeks treatment with AGE did not significantly improve endothelial function, vascular inflammation, oxidative stress or insulin resistance.

Keywords: Aged Garlic Extract; Diabetes; Endothelial function; Oxidative stress; Vascular inflammation.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Antioxidants / therapeutic use*
  • Cardiovascular Diseases / complications
  • Cardiovascular Diseases / epidemiology
  • Cardiovascular Diseases / prevention & control
  • Cohort Studies
  • Cross-Over Studies
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / diet therapy*
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / physiopathology
  • Diabetic Angiopathies / epidemiology
  • Diabetic Angiopathies / prevention & control*
  • Diabetic Cardiomyopathies / epidemiology
  • Diabetic Cardiomyopathies / prevention & control
  • Dietary Supplements*
  • Double-Blind Method
  • Endothelium, Vascular / physiopathology*
  • Female
  • Garlic / chemistry*
  • Humans
  • Insulin Resistance
  • Male
  • Middle Aged
  • Oxidative Stress
  • Pilot Projects
  • Plant Extracts / therapeutic use*
  • Risk Factors
  • United Kingdom / epidemiology
  • Vasculitis / complications
  • Vasculitis / epidemiology
  • Vasculitis / prevention & control


  • Antioxidants
  • Plant Extracts