Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations.
Plain language summary
It is generally accepted that certain diet and lifestyle choices contribute to a person’s risk of developing type 2 diabetes (T2D). In this meta-analysis, researchers set out to review previous studies and assess whether there is any evidence that the amount and type of carbohydrate (measured by Glycaemic Index (GI) and Glycaemic Load (GL)) in a person’s diet has a direct influence on their risk of developing T2D. The authors concluded with a high level of confidence that eating high GI and GL foods can lead to a higher risk of developing T2D. They suggest that nutrition advice that favours low GI and GL foods could produce significant cost savings for public healthcare.
While dietary factors are important modifiable risk factors for type 2 diabetes (T2D), the causal role of carbohydrate quality in nutrition remains controversial. Dietary glycemic index (GI) and glycemic load (GL) have been examined in relation to the risk of T2D in multiple prospective cohort studies. Previous meta-analyses indicate significant relations but consideration of causality has been minimal. Here, the results of our recent meta-analyses of prospective cohort studies of 4 to 26-y follow-up are interpreted in the context of the nine Bradford-Hill criteria for causality, that is: (1) Strength of Association, (2) Consistency, (3) Specificity, (4) Temporality, (5) Biological Gradient, (6) Plausibility, (7) Experimental evidence, (8) Analogy, and (9) Coherence. These criteria necessitated referral to a body of literature wider than prospective cohort studies alone, especially in criteria 6 to 9. In this analysis, all nine of the Hill's criteria were met for GI and GL indicating that we can be confident of a role for GI and GL as causal factors contributing to incident T2D. In addition, neither dietary fiber nor cereal fiber nor wholegrain were found to be reliable or effective surrogate measures of GI or GL. Finally, our cost-benefit analysis suggests food and nutrition advice favors lower GI or GL and would produce significant potential cost savings in national healthcare budgets. The high confidence in causal associations for incident T2D is sufficient to consider inclusion of GI and GL in food and nutrient-based recommendations.
Metabolic response to amylose-rich wheat-based rusks in overweight individuals.
European journal of clinical nutrition. 2018;(6):904-912
BACKGROUND/OBJECTIVES The amylose-amylopectin ratio influences starch properties. A higher amylose content is associated with slower starch digestion thus reducing the postprandial plasma glucose response and improving the overall postprandial metabolism. So far, limited evidence is available on the metabolic effect of wheat-based foods rich in amylose. This randomised controlled study investigated the acute metabolic effects of amylose-rich wheat-based rusks in overweight subjects focusing on potential mechanisms. SUBJECTS/METHODS Ten overweight subjects consumed in random order two test meals differing only in the carbohydrate source: rusks prepared with amylose-rich wheat flour (ARR) or conventional wheat flour (control). Blood samples were taken at fasting and over 4 h after the meal. Satiety and intestinal fermentation were evaluated by VAS and H2-breath test, respectively. RESULTS ARR reduced plasma glucose response during the first two hours after the meal and the desire to eat, and increased breath hydrogen concentration at 4 h (p < 0.05 for all). Moreover, according to computational models, the ARR slightly reduced intestinal glucose absorption in the first hour after the meal and increased the overall postprandial insulin sensitivity. CONCLUSIONS Rusks made with amylose-rich flour could be useful for improving postprandial glucose metabolism and reduce the desire to eat, thus possibly contributing to the prevention and treatment of overweight/obesity, impaired glucose tolerance or diabetes.
Intensive dietary intervention promoting the Mediterranean diet in people with high cardiometabolic risk: a non-randomized study.
Acta diabetologica. 2018;(3):219-226
AIMS: Mediterranean diet (MD) is acknowledged to exert a number of beneficial health effects. We assessed the efficacy and the durability of a 3-month intensive dietary intervention aimed at implementing the MD on body weight and cardiometabolic risk factors in subjects at high risk. METHODS One hundred and sixteen subjects participated in the study (71 assigned to the intensive intervention and 45 to the conventional intervention). The intensive intervention consisted of 12 weekly group educational meetings and a free-of-charge supply of meals prepared according to the MD model. The conventional intervention consisted of an individual education session along with monthly reinforcements of nutritional messages by the general practitioner. All participants were followed up for 9 months. RESULTS The two groups had similar pre-intervention characteristics. After the intervention, mean body weight decreased significantly in both groups (p < 0.001). However, the intervention group lost more weight (6.8 ± 4.0 vs. 0.7 ± 1.3, p < 0.0001) and showed a greater reduction in plasma glucose, triglycerides, blood pressure and an increase in HDL cholesterol than the control group (p < 0.01-p < 0.002). In the subgroup of participants with type 2 diabetes, there was a significant reduction in HbA1c level following the intensive (p < 0.0001) but not the conventional intervention. At follow-up, weight loss still persisted in the intervention group (p < 0.0001), while it was lost in the control group. Both interventions significantly reduced blood pressure in the long term (p < 0.001). A significant reduction in daily total energy intake was observed in both groups with a greater reduction in saturated fat and a higher increase in fibre intake in the intervention than in the control group (p < 0.009 and p < 0.001, respectively). CONCLUSIONS A 3-month intensive dietary intervention inspired to the traditional MD produced greater and more durable weight loss and improvement in cardiometabolic risk profile than the conventional intervention.
Clinical efficacy of bariatric surgery versus liraglutide in patients with type 2 diabetes and severe obesity: a 12-month retrospective evaluation.
Acta diabetologica. 2015;(2):331-6
AIMS: To evaluate the clinical efficacy of bariatric surgery vs medical therapy with liraglutide on weight loss, glycemic control and cardiovascular risk profile in patients with type 2 diabetes and severe obesity. METHODS A retrospective evaluation was conducted in 31 patients with type 2 diabetes and severe obesity who had undergone bariatric surgery and in 31 patients with type 2 diabetes and comparable body weight who had added liraglutide to their background medical treatment in the period 2009-2013. Anthropometric parameters, glycemic control, treatment of diabetes and other comorbidities, safety and side effects before and 12 months after treatment were assessed. RESULTS Age was 47 ± 8 years (mean ± SD) in bariatric surgery and 56 ± 9 years in medical treatment group (p < 0.001); body mass index before treatment was 44 ± 7 and 40 ± 4 kg/m(2) in bariatric surgery and medical treatment, respectively (p = 0.03). Twelve months after treatment, average weight loss was 38 ± 15 kg among bariatric surgery patients, and 5 ± 8 kg in medical treatment group (p < 0.001). Glycemic control improved in both groups with greater improvement in bariatric surgery patients. The UKPDS risk score decreased in both groups, although it remained higher in medical treatment than in bariatric surgery patients (p < 0.001). Of note, almost 60 % of patients on liraglutide met the target of glycated hemoglobin <7 % (53 mmol/mol) and lost ≥5 % of body weight. CONCLUSIONS In severely obese type 2 diabetic patients, bariatric surgery reduced body weight and improved overall metabolic control to a greater extent than medical treatment. Randomized clinical studies are necessary.
A CHO/fibre diet reduces and a MUFA diet increases postprandial lipaemia in type 2 diabetes: no supplementary effects of low-volume physical training.
Acta diabetologica. 2014;(3):385-93
The aim of the study was to evaluate the effects of a supervised physical training added to a healthy diet-rich in either carbohydrate and fibre (CHO/fibre) or monounsaturated fatty acids (MUFA)-on postprandial dyslipidaemia, an independent cardiovascular risk factor particularly relevant in type 2 diabetes (T2D). Participants were forty-five overweight/obese subjects with T2D, of both genders, in good blood glucose control with diet or diet+metformin, with normal fasting plasma lipids. According to a parallel groups 2 × 2 factorial design, participants were randomized to an 8-week isoenergetic intervention with a CHO/fibre or a MUFA diet, with or without a supervised low-volume aerobic training programme. The main outcome of the study was the incremental area under the curve (iAUC) of lipid concentrations in the plasma chylomicron+VLDL lipoprotein fraction, isolated by preparative ultracentrifugation (NCT01025856). Body weight remained stable during the trial in all groups. Physical fitness slightly improved with training (VO2 peak, 16 ± 4 vs. 15 ± 3 ml/kg/min, M ± SD, p < 0.05). Postprandial triglyceride and cholesterol iAUCs in plasma and chylomicron+VLDL fraction decreased after the CHO/fibre diet, but increased after the MUFA diet with a significant effect for diet by two-way ANOVA (p < 0.05). The addition of exercise training to either dietary intervention did not significantly influence postprandial lipid response. A diet rich in carbohydrates and fibre reduced postprandial triglyceride-rich lipoproteins compared with a diet rich in MUFA in patients with T2D. A supervised low-volume physical training did not significantly influence these dietary effects.
Liver fat is reduced by an isoenergetic MUFA diet in a controlled randomized study in type 2 diabetic patients.
Diabetes care. 2012;(7):1429-35
OBJECTIVE To evaluate the effects of qualitative dietary changes and the interaction with aerobic exercise training on liver fat content independent of weight loss in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS With use of a factorial 2 × 2 randomized parallel-group design, 37 men and 8 women, aged 35-70 years, with type 2 diabetes in satisfactory blood glucose control on diet or diet plus metformin treatment were assigned to one of the following groups for an 8-week period: 1) high-carbohydrate/high-fiber/low-glycemic index diet (CHO/fiber group), 2) high-MUFA diet (MUFA group), 3) high-carbohydrate/high-fiber/low-glycemic index diet plus physical activity program (CHO/fiber+Ex group), and 4) high-MUFA diet plus physical activity program (MUFA+Ex group). Before and after intervention, hepatic fat content was measured by (1)H NMR. RESULTS Dietary compliance was optimal and body weight remained stable in all groups. Liver fat content decreased more in MUFA (-29%) and MUFA+Ex (-25%) groups than in CHO/fiber (-4%) and CHO/fiber+Ex groups (-6%). Two-way repeated-measures ANOVA, including baseline values as covariate, showed a significant effect on liver fat content for diet (P = 0.006), with no effects for exercise training (P = 0.789) or diet-exercise interaction (P = 0.712). CONCLUSIONS An isocaloric diet enriched in MUFA compared with a diet higher in carbohydrate and fiber was associated with a clinically relevant reduction of hepatic fat content in type 2 diabetic patients independent of an aerobic training program and should be considered for the nutritional management of hepatic steatosis in people with type 2 diabetes.
Weight loss in obese type 2 diabetic patients on an intensive therapeutic programme: Importance of an initial short hospitalization period.
Nutrition, metabolism, and cardiovascular diseases : NMCD. 2008;(2):e1-2
A randomised controlled cross-over trial of aerobic training versus Qigong in advanced Parkinson's disease.
Europa medicophysica. 2006;(3):231-8
AIM: To investigate the effects of an aerobic training in subjects with Parkinson's disease (PD) as compared to a medical Chinese exercise (Qigong). METHODS DESIGN randomized controlled trial with a cross over design. SETTING PD out-patients referred to a Neurorehabilitation facility for the management of motor disability. SUBJECTS 26 PD patients in Hoehn and Yahr stage II to III under stable medication were randomly allocated to either Group AT1+QG2 (receiving 20 aerobic training sessions followed by 20 ''Qigong'' group sessions with 2 month interval between the interventions), or Group QG1+AT2 (performing the same treatments with an inverted sequence). MAIN OUTCOME MEASURES clinical effects of treatment were sought through the Unified Parkinson's Disease Rating Scale (UPDRS), Brown's Disability Scale (B'DS), six-Minute Walking Test (6MWT), Borg scale for breathlessness, Beck Depression Inventory (BDI) and Parkinson's Disease Questionnaire-39 items (PDQ-39). A spirometry test and maximum cardiopulmonary exercise test (CPET) were also performed to determine the pulmonary function, the metabolic and cardio-respiratory requests at rest and under exercise. All measures were taken immediately before and at the completion of each treatment phase. RESULTS The statistical analysis focusing on the evolution of motor disability and quality of life revealed a significant interaction effect between group and time for the 6MWT (time x group effect: F: 5.4 P=0.002) and the Borg scale (time x group effect: F: 4.2 P=0.009). Post hoc analysis showed a significant increase in 6MWT and a larger decrease in Borg score after aerobic training within each subgroup, whereas no significant changes were observed during Qigong. No significant changes over time were detected through the analysis of UPDRS, B'DS, BDI and PDQ-39 scores. The analysis of cardiorespiratory parameters showed significant interaction effects between group and time for the Double Productpeak (time x group effect: F: 7.7 P=0.0003), the VO(2peak) (time x group effect: F: 4.8 P=0.007), and the VO(2)/kg ratio (time x group effect: F: 4.3 P=0.009), owing to their decrease after aerobic training to an extent that was never observed after Qigong treatment. CONCLUSIONS Aerobic training exerts a significant impact on the ability of moderately disabled PD patients to cope with exercise, although it does not improve their self-sufficiency and quality of life.
Characteristics of some wheat-based foods of the Italian diet in relation to their influence on postprandial glucose metabolism in patients with type 2 diabetes.
The British journal of nutrition. 2001;(1):33-40
The present study was aimed at evaluating in patients with type 2 diabetes: (1) the glycaemic response to four starchy foods based on wheat, typical of the Italian diet; (2) the importance of some food characteristics in relation to their effects on postprandial glucose response. Seventeen patients with type 2 diabetes (eleven men and six women) participated in the study. All patients consumed, in random order and on alternate days, 50 g available carbohydrate provided by 90 g white bread and, according to a randomised procedure, an equivalent amount of carbohydrate provided by one (n 8) or two (n 9) of three other different test foods (g): pizza 85, potato dumplings 165, hard toasted bread 60. Foods had a similar nutrient composition. Plasma glucose response, measured for 180 min, was significantly lower after the potato dumplings than after white bread at 90 (P < 0.05), 120 (P < 0.01), and 150 (P < 0.05) min. No difference was observed in postprandial plasma insulin response after the various test foods. The percentage of starch hydrolysed after 5 h in vitro hydrolysis with alpha-amylase was about 30 % lower for potato dumplings than for the other foods. However, no differences in the resistant starch content, the rate of diffusion of simple sugars added to a dialysis tube containing the food, and the viscosity of digesta were observed among the test foods. Scanning electron microscopy of potato dumplings showed a compact structure compatible with impaired accessibility of starch to digestive enzymes. In conclusion, carbohydrate-rich foods typical of the Italian diet which are often consumed as an alternative to pasta dishes are not equivalent in terms of metabolic impact in diabetic patients. Due to their low blood glucose response, potato dumplings represent a valid alternative to other starchy foods in the diabetic diet. Food structure plays an important role in determining starch accessibility to digestion, thus influencing the postprandial blood glucose response.