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Background: The etiological role of vitamin D deficiency in glucose tolerance and type 2 diabetes is well defined. it can reduce insulin secretion and, therefore, impair glucose tolerance. The present study was designed to determine the effects of vitamin D supplementation on insulin resistance in type 2 diabetic patients. Materials and Methods: This study was a double-bind clinical trial. Fifty-seven diabetic patients (34 males and 23 females) being treated with oral hypoglycemic agents who had normal serum calcium level, were enrolled in the study. The study was conducted in winter (when the vitamin D is in its lowest level in Iran). The patients were randomly divided into 2 groups and received 1500 IU/d oral vitamin D3 or placebo for 1 month. Fasting glucose, insulin, C- peptide, serum 25-hydroxy-vitamin D and Quantitative Insulin Sensitivity Check Index (QUICKI) were evaluated before and after the treatment. Measurement of energy, macronutrients, fiber, vitamin E, vitamin C, Magnesium, Zinc, Calcium and vitamin D status intake was performed in the onset, during and at the end of the study. Results: The mean of primary serum level of 25-hydroxy-vitamin D was 10.42±10.67 ng/ml. 47 subjects (82.5%) out of 57 ones were vitamin D deficient. After the treatment, only 60% of patients in vitamin D-received group achieved normal level of 25-hydroxy-vitamin D. Fasting glucose and insulin decreased in vitamin D-received group, although it was not significant. Serum C-peptide level increased significantly in vitamin D-received group from 2.47±0.88 ng/ml (in pre-treatment stage) to 2.78±1.14 ng/ml (in post-treatment stage) (P<0.02). Serum Calcium level increased significantly in vitamin D-received group (P<0.04), however, it remained at a normal range. The mean of changes of QUICKI was significantly higher in vitamin D-received group than that of placebo group in post-treatment stage (P<0.03). It indicates that insulin resistance was reduced in this group. Conclusion: Results of this study suggest that vitamin D supplementation can reduce insulin resistance in type 2 diabetic patients and it should be, therefore, recomended to improve the control of diabetes, especially in winter.

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Background and Aim: Type 2 diabetes is a common metabolic disorder accompanied by increased risk of cardiovascular diseases, along with increased morbidity and mortality. In recent years, epidemiological evidence and clinical studies have indicated that dietary polyphenols and phytochemical-rich foods have key role in prevention of cardiovascular diseases, especially coronary heart disease and myocardial infarction. The current review was conducted to investigate the mechanism of the effects of polyphenols in natural foods on prevention of diabetes-induced cardiovascular diseases. Materials and Methods: “polyphenols”, “phenolic acids”, “anthocyanins”, “flavonoids”, and “lignans” in combination with “type 2 diabetes”, “insulin resistance”, “cardiovascular disease”, “endothelial dysfunction”, “oxidative stress”, “inflammation”, “lipid disorders”, and “hypertension” were used as key words for search in PubMed between 1990 and 2013. Cellular studies, animal models and clinical trials with appropriate design, and review article with high quality were used. Results: Dietary polyphenols have high potential to improve lipid profiles through decrease in digestion and ingestion of dietary fats, increase in turnover and excretion of cholesterol, reduction of synthesis of atherogenic apo lipoproteins, and inhibition of cholesterol and triglycerides synthesis. These compounds protect vascular endothelium against oxidative damages and inflammatory processes, improve function of vascular endothelium, modify the pathways related to platelets and coagulation, and even protect cardiac tissue and improve myocardial hemodynamics. ‍Conclusion: Higher consumption of foods containing polyphenols and using polyphenol-rich natural extract can be useful in decreasing the risk of development of cardiovascular diseases in type 2 diabetic patients.

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Background and Aim: The aim of this study was to determine the effect of legume intake in therapeutic lifestyle change (TLC) on fasting insulin, fasting blood glucose, HbA1c and homeostasis model assessment insulin resistance (HOMA-IR) in patients with type 2 diabetes. Materials and Methods: In this randomized crossover trial, 31 subjects with type 2 diabetes in the age range of 50 to 80 years were selected. The subjects were randomly assigned to two groups receiving diets of therapeutic lifestyle change or the therapeutic lifestyle change with legumes (replacing meat with 2 servings of legumes in their therapeutic lifestyle change diet, three days a week). Period of each diet was 8 weeks with a 4 week washout period. Fasting blood samples were taken to measure the fasting insulin, fasting plasma glucose, HbA1c HOMA-IR. Results: After 8 weeks of intervention, fasting plasma glucose, fasting insulin and HOMA-IR in both diets significantly reduced compared with baseline values (P<0.05). Compared with the TLC diet, in TLC diet with legumes, fasting insulin, fasting plasma glucose, and HOMA-IR was significantly decreased (P<0.05). No significant change was observed in HbA1c concentration. Conclusion: Replacement of 2 servings of legumes instead of meat 3 days a week in the TLC diet resulted in improved glycemic control and insulin resistance among type 2 diabetic patients.