Effects on cardiovascular risk factors of a low- vs high-glycemic index Mediterranean diet in high cardiometabolic risk individuals: the MEDGI-Carb study.

BACKGROUND: The role of dietary Glycemic Index (GI), independently of fiber intake, in modulating cardiovascular disease (CVD) risk among non-diabetic individuals has not been fully elucidated. OBJECTIVE: To evaluate the effects of a low- versus a high-GI diet, based on a Mediterranean dietary pattern, on cardiometabolic risk factors in individuals at high CVD risk, participating in the MEDGI-Carb intervention study. SUBJECTS AND METHODS: 160 individuals, aged 30-69 years, BMI 25-37 kg/m2, with a waist circumference >102 cm (males) or >88 cm (females) and one feature of the metabolic syndrome, participated in a multi-national (Italy, Sweden, USA) randomized controlled parallel group trial. Participants were assigned to a low GI (< 55) or high-GI MedDiet ( > 70) for 12 weeks. The diets were isoenergetic and similar for available carbohydrate (270 g/d) and fiber (35 g/d) content. Fasting metabolic parameters were evaluated in the whole cohort, while an 8-h triglyceride profile (after standard breakfast and lunch) was evaluated only in the Italian cohort. RESULTS: Blood pressure and most fasting metabolic parameters improved at the end of the dietary intervention (time effect, p < 0.05 for all); however, no differences were observed between the low- and the high-GI MedDiet groups (time x group effect; p > 0.05 for all). Conversely, the low-GI diet, compared with high-GI diet, significantly reduced the 8-h triglyceride profile (p < 0.017, time*group effect) that was measured only in the Italian cohort. However, it induced a reduction of plasma triglycerides after lunch (tAUC) that was of only borderline statistically significance (p = 0.065). CONCLUSIONS: Consuming a low-GI in comparison with a high-GI MedDiet does not differentially affect the major cardiometabolic risk factors at fasting in individuals at increased cardiometabolic risk. Conversely, it could reduce postprandial plasma triglycerides. CLINICAL TRIAL REGISTRY NUMBER: NCT03410719, ( https://clinicaltrials.gov ).

Differential Responders to a Mixed Meal Tolerance Test Associated with Type 2 Diabetes Risk Factors and Gut Microbiota-Data from the MEDGI-Carb Randomized Controlled Trial.

The global prevalence of type 2 diabetes mellitus (T2DM) has surged in recent decades, and the identification of differential glycemic responders can aid tailored treatment for the prevention of prediabetes and T2DM. A mixed meal tolerance test (MMTT) based on regular foods offers the potential to uncover differential responders in dynamical postprandial events. We aimed to fit a simple mathematical model on dynamic postprandial glucose data from repeated MMTTs among participants with elevated T2DM risk to identify response clusters and investigate their association with T2DM risk factors and gut microbiota. Data were used from a 12-week multi-center dietary intervention trial involving high-risk T2DM adults, comparing high- versus low-glycemic index foods within a Mediterranean diet context (MEDGICarb). Model-based analysis of MMTTs from 155 participants (81 females and 74 males) revealed two distinct plasma glucose response clusters that were associated with baseline gut microbiota. Cluster A, inversely associated with HbA1c and waist circumference and directly with insulin sensitivity, exhibited a contrasting profile to cluster B. Findings imply that a standardized breakfast MMTT using regular foods could effectively distinguish non-diabetic individuals at varying risk levels for T2DM using a simple mechanistic model.

The effects of Mediterranean diets with low or high glycemic index on plasma glucose and insulin profiles are different in adult men and women: Data from MEDGI-Carb randomized clinical trial.

BACKGROUND & AIMS: Recent evidence suggests that the ability to regulate glucose and insulin homeostasis is different in men and women. Against this background, it has been hypothesized that the impact on daily plasma glucose and insulin profiles of the glycemic index (GI) of the habitual diet may differ according to sex. The aim of this study is to evaluate whether 8-h average plasma glucose and insulin profiles during a low- or a high-GI diet in individuals at high risk of developing type 2 diabetes are influenced by sex. METHODS: We conducted a randomized, controlled, parallel group dietary intervention, comparing high-versus low-GI diets in a multi-national (Italy, Sweden, and the United States) sample of 156 adults at risk for type 2 diabetes. For 12 weeks, 82 vs 74 participants consumed either a low-GI or high-GI Mediterranean diet, respectively. The two experimental diets contained the same quantity of available carbohydrate (270 g/d) and fiber (35 g/d) and the same foods and beverages, except for the major sources of starch that was specific to the low-GI and high-GI groups (pasta, brown rice, flatbread, all bran, and wheat bread plus rye and seeds, vs jasmine rice, potato, couscous, wholegrain bread, and rusks). At baseline and after the intervention plasma glucose and insulin profiles were evaluated for 8 h in the two intervention groups - separately for men and women - with both breakfast and lunch resembling food choices of the assigned diet. RESULTS: One hundred fifty-six adults (82 women, 74 men) with at least two traits of the metabolic syndrome completed the intervention. In women, the high-GI induced significantly higher (23%, p < 0.05) 8-h average plasma glucose concentrations in comparison to the low-GI diet already on the first day of the intervention; the difference increased up to 37% (p < 0.05) after 12 weeks of diet. Conversely, there were no significant differences between the two diets in men. These results were confirmed by the two-way analysis of variance showing a statistically significant interaction between the effects of sex and diet on the glucose profile after breakfast and lunch (F = 7.887, p = 0.006). CONCLUSION: The results of our intervention show that women, compared to men, are more sensitive to the metabolic effects of the dietary GI. This has a strong clinical and scientific relevance and, if confirmed in further studies, it might have important implications for dietary strategies for diabetes and cardiovascular disease prevention in the context of personalized nutrition. REGISTRATION NUMBER OF CLINICAL TRIAL: Clinicaltrials.gov n. NCT03410719.

Evaluation of Subjective Appetite Assessment under Free-Living vs. Controlled Conditions: A Randomized Crossover Trial Comparing Whole-Grain Rye and Refined Wheat Diets (VASA-Home).

BACKGROUND: Accurate assessment of self-reported appetite under free-living conditions is warranted to conduct large-scale intervention studies measuring appetite at a feasible cost. However, the performance of visual analogue scales (VASs) for this purpose has not been widely examined. METHOD: This randomized crossover trial was conducted to evaluate VASs in free-living vs. clinic-based settings and to assess appetite response following hypocaloric whole-grain rye and refined wheat diets. Twenty-nine healthy adults with overweight or obesity continuously answered VAS questions about their perceived appetite from morning to evening. RESULTS: No differences in whole-day VAS scores (primary outcome) between clinic-based and free-living settings were observed, whereas measures of total area under the curve (tAUC) showed increased fullness in clinic-based interventions of 7% (p < 0.008) for whole-day responses and 13% (p < 0.03) following a snack. Appetite responses for a whole day did not differ between diets whereas rye-based dinners induced 12% (p < 0.016) higher fullness and reduced hunger by 17% (p < 0.02) irrespective of setting. A reduction in hunger of 15% (p < 0.05) was also observed following rye-based vs. wheat-based lunches. CONCLUSION: The results suggest that the VAS is valid for evaluation of appetite responses between diets under free-living conditions. No difference in self-reported appetite over the whole day was found after whole-grain rye vs. refined wheat-based diets, but there were some suggested differences at certain postprandial periods, in individuals with overweight or obesity.

Sixteen-week multicentre randomised controlled trial to study the effect of the consumption of an oat beta-glucan-enriched bread versus a whole-grain wheat bread on glycaemic control among persons with pre-diabetes: a study protocol of the CarbHealth study.

INTRODUCTION: In 2012, the estimated global prevalence of pre-diabetes was 280 million, and the prevalence is expected to rise to 400 million by 2030. Oat-based foods are a good source of beta-glucans, which have been shown to lower postprandial blood glucose. Studies to evaluate the effectiveness of the long-term intake of beta-glucan-enriched bread as part of a habitual diet among individuals with pre-diabetes are needed. Therefore, we designed a multicentre intervention study in adults with pre-diabetes to investigate the effects of consumption of an oat-derived beta-glucan-enriched bread as part of a normal diet on glycated haemoglobin (HbA1c) in comparison to consumption of whole-grain wheat bread. METHODS AND ANALYSIS: The CarbHealth trial is a multicentre double-blind randomised controlled 16-week dietary intervention trial in participants 40-70 years of age with a body mass index of ≥27 kg/m2 and HbA1c of 35-50 mmol/mol. The study is conducted at four universities located in Norway, Sweden and Germany and uses intervention breads specifically designed for the trial by Nofima AS. The aim is to recruit 250 participants. The primary outcome is the difference in HbA1c between the intervention and the control groups. The main analysis will include intervention group, study centre and baseline HbA1c as independent variables in an analysis of covariance model. ETHICS AND DISSEMINATION: The study protocol was approved by respective ethical authorities in participating countries. The results of the study will be communicated through publication in international scientific journals and presentations at (inter)national conferences. TRIAL REGISTRATION NUMBER: NCT04994327.

Differential Glycemic Effects of Low- versus High-Glycemic Index Mediterranean-Style Eating Patterns in Adults at Risk for Type 2 Diabetes: The MEDGI-Carb Randomized Controlled Trial.

A Mediterranean-style healthy eating pattern (MED-HEP) supports metabolic health, but the utility of including low-glycemic index (GI) foods to minimize postprandial glucose excursions remain unclear. Therefore, we investigated the relative contribution of GI towards improvements in postprandial glycemia and glycemic variability after adopting a MED-HEP. We conducted a randomized, controlled dietary intervention, comparing high- versus low-GI diets in a multi-national (Italy, Sweden, and the United States) sample of adults at risk for type 2 diabetes. For 12 weeks, participants consumed either a low-GI or high-GI MED-HEP. We assessed postprandial plasma glucose and insulin responses to high- or low-GI meals, and daily glycemic variability via continuous glucose monitoring at baseline and post-intervention. One hundred sixty adults (86 females, 74 males; aged 55 ± 11 y, BMI 31 ± 3 kg/m2, mean ± SD) with ≥two metabolic syndrome traits completed the intervention. Postprandial insulin concentrations were greater after the high-GI versus the low-GI test meals at baseline (p = 0.004), but not post-intervention (p = 0.17). Postprandial glucose after the high-GI test meal increased post-intervention, being significantly higher than that after the low-GI test meal (35%, p < 0.001). Average daily glucose concentrations decreased in both groups post-intervention. Indices of 24-h glycemic variability were reduced in the low-GI group as compared to baseline and the high-GI intervention group. These findings suggest that low-GI foods may be an important feature within a MED-HEP.

Changes in dietary carbon footprint over ten years relative to individual characteristics and food intake in the Västerbotten Intervention Programme.

The objective was to examine 10-year changes in dietary carbon footprint relative to individual characteristics and food intake in the unique longitudinal Västerbotten Intervention Programme, Sweden. Here, 14 591 women and 13 347 men had been followed over time. Food intake was assessed via multiple two study visits 1996-2016, using a 64-item food frequency questionnaire. Greenhouse gas emissions (GHGE) related to food intake, expressed as kg carbon dioxide equivalents/1000 kcal and day, were estimated. Participants were classified into GHGE quintiles within sex and 10-year age group strata at both visits. Women and men changing from lowest to highest GHGE quintile exhibited highest body mass index within their quintiles at first visit, and the largest increase in intake of meat, minced meat, chicken, fish and butter and the largest decrease in intake of potatoes, rice and pasta. Women and men changing from highest to lowest GHGE quintile exhibited basically lowest rates of university degree and marriage and highest rates of smoking within their quintiles at first visit. Among these, both sexes reported the largest decrease in intake of meat, minced meat and milk, and the largest increase in intake of snacks and, for women, sweets. More research is needed on how to motivate dietary modifications to reduce climate impact and support public health.

Climate impact from diet in relation to background and sociodemographic characteristics in the Västerbotten Intervention Programme.

OBJECTIVE: The objective of this study was to examine climate impact from diet across background and sociodemographic characteristics in a population-based cohort in northern Sweden. DESIGN: A cross-sectional study within the Västerbotten Intervention Programme. Dietary data from a 64-item food frequency questionnaire collected during 1996-2016 were used. Energy-adjusted greenhouse gas emissions (GHGE) for all participants, expressed as kg carbon dioxide equivalents/day and 4184 kJ (1000 kcal), were estimated using data from life cycle analyses. Differences in background and sociodemographic characteristics were examined between participants with low and high GHGE from diet, respectively. The variables evaluated were age, BMI, physical activity, marital status, level of education, smoking, and residence. SETTING: Västerbotten county in northern Sweden. PARTICIPANTS: In total, 46 893 women and 45 766 men aged 29-65 years. RESULTS: Differences in GHGE from diet were found across the majority of examined variables. The strongest associations were found between GHGE from diet and age, BMI, education, and residence (all P < 0·001), with the highest GHGE from diet found among women and men who were younger, had a higher BMI, higher educational level, and lived in urban areas. CONCLUSIONS: This study is one of the first to examine climate impact from diet across background and sociodemographic characteristics. The results show that climate impact from diet is associated with age, BMI, residence and educational level amongst men and women in Västerbotten, Sweden. These results define potential target populations where public health interventions addressing a move towards more climate-friendly food choices and reduced climate impact from diet could be most effective.