Nuts; inflammation and insulin resistance
The beneficial effects of nut consumption on cardiovascular disease (CVD) have been widely documented. These protective effects are mainly attributed to the role of nuts in the metabolism of lipids and lipoproteins. As chronic inflammation is a key early stage in the atherosclerotic process that predicts future CVD events and is closely related to the pathogenesis of insulin resistance; many recent studies have focused on the potential effect of nut consumption on inflammation and insulin resistance. Through different mechanisms; some components of nuts such as magnesium; fiber; alpha-linolenic acid; L-arginine; antioxidants and MUFA may protect against inflammation and insulin resistance. This review evaluates the epidemiologic and experimental evidence in humans demonstrating an association between nut consumption and these two emergent cardio-protective mechanisms.
Almond consumption improved glycemic control and lipid profiles in patients with type 2 diabetes mellitus
Almond consumption is associated with ameliorations in obesity; hyperlipidemia; hypertension; and hyperglycemia. The hypothesis of this 12-week randomized crossover clinical trial was that almond consumption would improve glycemic control and decrease the risk for cardiovascular disease in 20 Chinese patients with type 2 diabetes mellitus (T2DM) (9 male; 11 female; 58 years old; body mass index; 26 kg/m2) with mild hyperlipidemia. After a 2-week run-in period; patients were assigned to either a control National Cholesterol Education Program step II diet (control diet) or an almond diet for 4 weeks; with a 2-week washout period between alternative diets. Almonds were added to the control diet to replace 20% of total daily calorie intake. Addition of approximately 60 g almonds per day increased dietary intakes of fiber; magnesium; polyunsaturated fatty acid; monounsaturated fatty acid; and vitamin E. Body fat determined with bioelectrical impedance analysis was significantly lower in patients consuming almonds (almonds vs control: 29.6% vs 30.4%). The almond diet enhanced plasma a-tocopherol level by a median 26.8% (95% confidence intervals; 15.1-36.6) compared with control diet. Furthermore; almond intake decreased total cholesterol; low-density lipoprotein cholesterol; and the ratio of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol by 6.0% (1.6-9.4); 11.6% (2.8-19.1); and 9.7% (0.3-20.9); respectively. Plasma apolipoprotein (apo) B levels; apo B/apo A-1 ratio; and nonesterified fatty acid also decreased significantly by 15.6% (5.1-25.4); 17.4% (2.8-19.9); and 5.5% (3.0-14.4); respectively. Compared with subjects in the control diet; those in the almond diet had 4.1% (0.9-12.5); 0.8% (0.4-6.3); and 9.2% (4.4-13.2) lower levels of fasting insulin; fasting glucose; and homeostasis model assessment of insulin resistance index; respectively. Our results suggested that incorporation of almonds into a healthy diet has beneficial effects on adiposity; glycemic control; and the lipid profile; thereby potentially decreasing the risk for cardiovascular disease in patients with type 2 diabetes mellitus.
Effects of one serving of mixed nuts on serum lipids; insulin resistance and inflammatory markers in patients with the metabolic syndrome
BACKGROUND AND AIMS: Knowledge of the effect of nut consumption on metabolic syndrome (MetS) components is limited. We assessed the effects of nut intake on adiposity; serum lipids; insulin resistance; and inflammatory biomarkers in patients with MetS. METHODS AND RESULTS: In a randomized; parallel-group; 12-week feeding trial; 50 patients with MetS were given recommendations for a healthy diet with or without supplementation with 30g/day of raw nuts (15g walnuts; 7.5g almonds and 7.5g hazelnuts) (Nut and Control diet groups; respectively). Adiposity measures; serum lipids; insulin; Homeostasis Model Assessment (HOMA); interleukin-6 (IL-6) and other inflammatory biomarkers; and 48-h fecal fat were determined basally and at study's completion. Moderate weight loss; decreased adiposity; and lower blood pressure occurred similarly after both diets. The Control; but not the Nut diet; was associated with significant (P<0.05) reduction of LDL-cholesterol; with mean changes of -0.36 versus -0.13mmol/L; respectively (between-group differences; P=0.154). The Nut diet reduced fasting insulin by 2.60muU/mL (95% CI; -4.62 to -0.59) and HOMA-insulin resistance by 0.72 (-1.28 to -0.16) (P<0.05 versus Control diet; both). Among inflammatory markers; the Nut diet resulted in changes of median plasma IL-6 of -1.1ng/L (-2.7 to -0.1; P=0.035 versus Control diet); but adjustment for weight loss attenuated the significance of the association. Stool fat decreased with the Control diet and slightly increased with the Nut diet (P<0.05 for between-group differences). CONCLUSION: Patients with MetS show decreased lipid responsiveness but improved insulin sensitivity after daily intake of 30g of mixed nuts.
Effects of walnut consumption on endothelial function in type 2 diabetic subjects: a randomized controlled crossover trial
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.
A randomized behavioural trial targeting glycaemic index improves dietary; weight and metabolic outcomes in patients with type 2 diabetes
OBJECTIVE: Glycaemic index (GI) reflects the postprandial glucose response of carbohydrate-containing foods. A diet with lower GI may improve glycaemic control in people with diabetes. The purpose of the present study was to evaluate the change in outcomes following a behavioural intervention which promoted lower-GI foods among adults with diabetes. DESIGN: A pre-test-post-test control group design was used with participants randomly assigned to an immediate (experimental) or delayed (control) treatment group. The intervention included a 9-week; group-based intervention about carbohydrate and the glycaemic index. Dietary; anthropometric and metabolic measures were obtained pre/post-intervention in both groups and at 18-week follow-up for the immediate group. SETTING: The study was conducted in a rural community in the north-eastern USA. SUBJECTS: Adults having type 2 diabetes mellitus for > or =1 year; aged 40-70 years and not requiring insulin therapy (n 109) were recruited. RESULTS: Following the intervention; mean dietary GI (P < 0.001); percentage of energy from total fat (P < 0.01) and total dietary fiber (P < 0.01) improved in the immediate compared with the delayed group. Mean BMI (P < 0.0001); fasting plasma glucose (P = 0.03); postprandial glucose (P = 0.02); fructosamine (P = 0.02) and insulin sensitivity factor (P = 0.04) also improved in the immediate group compared with the delayed group. Mean waist circumference among males (P < 0.01) and body weight among males and females (P < 0.01) were significantly different between treatment groups. CONCLUSIONS: Educating clients about carbohydrate and the glycaemic index can improve dietary intake and health outcomes among adults with type 2 diabetes.
Effects of a Mediterranean-style diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes: a randomized trial
BACKGROUND: Low-carbohydrate and low-fat calorie-restricted diets are recommended for weight loss in overweight and obese people with type 2 diabetes. OBJECTIVE: To compare the effects of a low-carbohydrate Mediterranean-style or a low-fat diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes. DESIGN: Single-center; randomized trial. Randomization was computer-generated and unstratified. Allocation was concealed in sealed study folders held in a central; secure location until participants gave informed consent. Participants and investigators were aware of treatment assignment; and assessors of the primary outcome were blinded. SETTING: Teaching hospital in Naples; Italy. PATIENTS: 215 overweight people with newly diagnosed type 2 diabetes who were never treated with antihyperglycemic drugs and had hemoglobin A(1c) (HbA(1c)) levels less than 11%. INTERVENTION: Mediterranean-style diet (<50% of daily calories from carbohydrates) (n = 108) or a low-fat diet (<30% of daily calories from fat) (n = 107). MEASUREMENTS: Start of antihyperglycemic drug therapy; defined by protocol as indicated for follow-up HbA(1c) level greater than 7% (primary outcome); and changes in weight; glycemic control; and coronary risk factors (secondary outcomes). RESULTS: After 4 years; 44% of patients in the Mediterranean-style diet group and 70% in the low-fat diet group required treatment (absolute difference; -26.0 percentage points [95% CI; -31.1 to -20.1 percentage points]; hazard ratio; 0.63 [CI; 0.51 to 0.86]; hazard ratio adjusted for weight change; 0.70 [CI; 0.59 to 0.90]; P < 0.001). Participants assigned to the Mediterranean-style diet lost more weight and experienced greater improvements in some glycemic control and coronary risk measures than did those assigned to the low-fat diet. LIMITATIONS: Investigators responsible for initiating drug therapy were not blinded to treatment assignment. Dietary intake was self-reported. CONCLUSION: Compared with a low-fat diet; a low-carbohydrate; Mediterranean-style diet led to more favorable changes in glycemic control and coronary risk factors and delayed the need for antihyperglycemic drug therapy in overweight patients with newly diagnosed type 2 diabetes.
Oleic acid and peanut oil high in oleic acid reverse the inhibitory effect of insulin production of the inflammatory cytokine TNF-alpha both in vitro and in vivo systems
BACKGROUND: Chronic inflammation is a key player in pathogenesis. The inflammatory cytokine; tumor necrosis factor-alpha is a well known inflammatory protein; and has been a therapeutic target for the treatment of diseases such as Rheumatoid Arthritis and Crohn's Disease. Obesity is a well known risk factor for developing non-insulin dependent diabetes melitus. Adipose tissue has been shown to produce tumor necrosis factor-alpha; which has the ability to reduce insulin secretion and induce insulin resistance. Based on these observations; we sought to investigate the impact of unsaturated fatty acids such as oleic acid in the presence of TNF-alpha in terms of insulin production; the molecular mechanisms involved and the in vivo effect of a diet high in oleic acid on a mouse model of type II diabetes; KKAy. METHODS: The rat pancreatic beta cell line INS-1 was used as a cell biological model since it exhibits glucose dependent insulin secretion. Insulin production assessment was carried out using enzyme linked immunosorbent assay and cAMP quantification with competitive ELISA. Viability of TNF-alpha and oleic acid treated cells was evaluated using flow cytometry. PPAR-gamma translocation was assessed using a PPRE based ELISA system. In vivo studies were carried out on adult male KKAy mice and glucose levels were measured with a glucometer. RESULTS: Oleic acid and peanut oil high in oleic acid were able to enhance insulin production in INS-1. TNF-alpha inhibited insulin production but pre-treatment with oleic acid reversed this inhibitory effect. The viability status of INS-1 cells treated with TNF-alpha and oleic acid was not affected. Translocation of the peroxisome proliferator- activated receptor transcription factor to the nucleus was elevated in oleic acid treated cells. Finally; type II diabetic mice that were administered a high oleic acid diet derived from peanut oil; had decreased glucose levels compared to animals administered a high fat diet with no oleic acid. CONCLUSION: Oleic acid was found to be effective in reversing the inhibitory effect in insulin production of the inflammatory cytokine TNF-alpha. This finding is consistent with the reported therapeutic characteristics of other monounsaturated and polyunsaturated fatty acids. Furthermore; a diet high in oleic acid; which can be easily achieved through consumption of peanuts and olive oil; can have a beneficial effect in type II diabetes and ultimately reverse the negative effects of inflammatory cytokines observed in obesity and non insulin dependent diabetes mellitus.
Functional foods for health: Focus on diabetes
Type 2 diabetes is one of the fastest growing public health problems worldwide. Menopause may present additional challenges for women who have diabetes by increasing the risk for cardiovascular disease (CVD) and making blood glucose control more difficult. Functional foods may have the potential to improve glycemic control; but little evidence is known about the efficacy of these foods. The purpose of this literature review is to establish a recommendation for the intake of functional foods in a healthy diet - such as nuts; omega-3 fatty acids (FAs) and cinnamon - for the glycemic control in type 2 diabetes. Nuts and omega-3 FAs appear to have an overall beneficial effect on CVD; however; their effect on glucose homeostasis is uncertain. In addition; cinnamon appears to inconsistently improve glycemic parameters in diabetic patients. Overall; more research on the potential effect of all of these functional foods on patients with type 2 diabetes is needed to able to make specific recommendations. In conclusion; there is reason to consider the inclusion of nuts and fish; as a source of omega-3 FAs; in the diets of individuals with diabetes in view of their potential to reduce CVD risk; even though their ability to influence overall glycemic control remains to be established.
Long-term effects of increased dietary polyunsaturated fat from walnuts on metabolic parameters in type II diabetes
Background/Objectives:Most dietary interventions have metabolic effects in the short term; but long-term effects may require dietary fat changes to influence body composition and insulin action. This study assessed the effect of sustained high polyunsaturated fatty acids (PUFA) intake through walnut consumption on metabolic outcomes in type II diabetes.Subjects/Methods:Fifty overweight adults with non-insulin-treated diabetes (mean age 54+/-8.7 years) were randomized to receive low-fat dietary advice +/-30 g per day walnuts targeting weight maintenance (around 2000 kcal; 30% fat) for 1 year. Differences between groups were assessed by changes in anthropometric values (body weight; body fat; visceral adipose tissue) and clinical indicators of diabetes over treatment time using the general linear model.Results:The walnut group consumed significantly more PUFA than the control (P=0.035); an outcome attributed to walnut consumption (contributing 67% dietary PUFA at 12 months). Most of the effects were seen in the first 3 months. Despite being on weight maintenance diets; both groups sustained a 1-2 kg weight loss; with no difference between groups (P=0.680). Both groups showed improvements in all clinical parameters with significant time effects (P<0.004); bar triacylglycerol levels; but these were just above normal to begin with. The walnut group produced significantly greater reductions in fasting insulin levels (P=0.046); an effect seen largely in the first 3 months.Conclusions:Dietary fat can be manipulated with whole foods such as walnuts; producing reductions in fasting insulin levels. Long-term effects are also apparent but subject to fluctuations in dietary intake if not of the disease process.
Effect of a low-glycemic index or a high-cereal fiber diet on type 2 diabetes: a randomized trial
CONTEXT: Clinical trials using antihyperglycemic medications to improve glycemic control have not demonstrated the anticipated cardiovascular benefits. Low-glycemic index diets may improve both glycemic control and cardiovascular risk factors for patients with type 2 diabetes but debate over their effectiveness continues due to trial limitations. OBJECTIVE: To test the effects of low-glycemic index diets on glycemic control and cardiovascular risk factors in patients with type 2 diabetes. DESIGN; SETTING; AND PARTICIPANTS: A randomized; parallel study design at a Canadian university hospital research center of 210 participants with type 2 diabetes treated with antihyperglycemic medications who were recruited by newspaper advertisement and randomly assigned to receive 1 of 2 diet treatments each for 6 months between September 16; 2004; and May 22; 2007. INTERVENTION: High-cereal fiber or low-glycemic index dietary advice. MAIN OUTCOME MEASURES: Absolute change in glycated hemoglobin A(1c) (HbA(1c)); with fasting blood glucose and cardiovascular disease risk factors as secondary measures. RESULTS: In the intention-to-treat analysis; HbA(1c) decreased by -0.18% absolute HbA(1c) units (95% confidence interval [CI]; -0.29% to -0.07%) in the high-cereal fiber diet compared with -0.50% absolute HbA(1c) units (95% CI; -0.61% to -0.39%) in the low-glycemic index diet (P < .001). There was also an increase of high-density lipoprotein cholesterol in the low-glycemic index diet by 1.7 mg/dL (95% CI; 0.8-2.6 mg/dL) compared with a decrease of high-density lipoprotein cholesterol by -0.2 mg/dL (95% CI; -0.9 to 0.5 mg/dL) in the high-cereal fiber diet (P = .005). The reduction in dietary glycemic index related positively to the reduction in HbA(1c) concentration (r = 0.35; P < .001) and negatively to the increase in high-density lipoprotein cholesterol (r = -0.19; P = .009). CONCLUSION: In patients with type 2 diabetes; 6-month treatment with a low-glycemic index diet resulted in moderately lower HbA(1c) levels compared with a high-cereal fiber diet.