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Considering the dramatically increasing incidence of type 2 diabetes (T2D), decreasing glycemic variability in T2D patients is a key challenge to limit the occurrence of diabetic complications. Diet appears as one potential lever that can be set up above medications. Particularly, the ingestion of foods with a high content in slowly digestible starch (SDS) demonstrated both lower postprandial glycemic and insulin responses in healthy and insulin resistant subjects. This study aimed at designing a full high-SDS diet by selecting high-SDS starchy food products and at studying its impact on glycemic response and variability in T2D.
Materials and methods
This pilot randomized controlled cross-over study included eight T2D patients (HbA1c = 7.0 ± 0.2%, BMI = 31.7 ± 2.1 kg/m2, treated by Metformin & Sitagliptin) who consumed twice, for one week a controlled diet containing starchy food products screened and selected to be either High (High-SDS) or Low (Low-SDS) in SDS, as determined by the SDS in-vitro method developed by Englyst et al. During each diet period, the glycemic profile was monitored for 6 days using a Continuous Glucose Monitoring System (CGMS). Multiple metrics related to variability and glycemic responses were calculated.
222 SDS analyses were realized on commercial food products as consumed. 23 High-SDS and 20 Low-SDS food items with associated specific cooking instructions were selected to design two diets consistent with local T2D recommendations. The High-SDS diet demonstrated a significantly higher SDS content compared to the Low-SDS diet (61.6 vs 11.6 g/day; p < 0.0001), mainly driven by selected pasta, rice and high-SDS biscuits (75.6% of the consumed SDS content). The % of total daily energy intake (TDEI) for all macronutrients remained similar between diets (p > 0.05) and the carbohydrate content specifically represented 49 ± 1 % and 47 ± 2 % of the TDEI for High-SDS and Low-SDS diets, respectively. With the high-SDS diet, the Mean Amplitude of Glycemic Excursion, a key parameter of glycemic variability, was significantly decreased (79.6 for Low-SDS vs 61.6 mg/dL for High-SDS; p = 0.0067). The significant correlation between the meals SDS contents and various glycemic parameters such as postprandial iAUC, tAUC (up to 180 min) or peak value strengthen this finding (p < 0.05 for all).
It was the first demonstration that a diet including selected starchy food items and cooking recommendations designed to favor products’ high SDS content beneficially impacts glycemic profile in T2D subjects. Carefully selecting starchy food may be a simple and valuable tool to improve glycemic control in T2D.
Starch is one of the major sources of carbohydrates (CHO) contributing to about 50–70% of the daily energy intake in human diet. Processed foods contribute to an important part of daily energy intake, especially in occidental countries. During food processing, starch undergoes dramatic changes when heated in the presence of water or high pressure. The objective of this work was to evaluate the impact of controlling food processes on starch digestibility profile in cereal-based foods and the interest of preserving starch in its native, slowly digestible, form on in vivo metabolic fate.
Four different food processes were evaluated: extrusion, dry bread, soft cake and rotary-moulded biscuit. The resulting differences in gelatinization of each product translated to different SDS levels. Imaging techniques (X-ray diffraction, microtomography and electronic microscopy) were used to investigate the changes in SDS structure obtained through the different food processes. For in vivo evaluation, 12 healthy subjects were recruited and consumed a portion of 50 g of available CHOs of each product, in a crossover design. Glycemic and insulin responses were evaluated over 120 minutes in postprandial period.
We showed that rotary molding technology preserved starch in its intact form and provided the highest SDS content (28g/100g) when the three other technologies (dried bread, soft cake and extrusion) led to SDS content below 3g/100 g. In addition, the lowest SDS contents are explained by a higher level of starch structure disruption which translated in a shift from crystalline structure into amorphous one. These data were linked to in vivo results. The global analysis for GI indicated that a significant difference existed among the foods’ mean GI values (p < 0.0001). Rotary product showed the lowest GI values. The soft, the dried bread had medium GI and extruded product had the highest GI with 77. The global analysis for II indicated that a significant difference existed among the foods’ mean II values (p < 0.0001), with the same order as for GI values. In addition, a portion of rotary-molded biscuit decreased significantly the glycemic peak by 1 mM compared to the 3 other products.
Decrease of postprandial glycemia is a meaningful target in the prevention of metabolic diseases. This can be achieved through the modification of dietary factors such as starch digestibility.
Glucose intolerance and type 2 diabetes are increasing worldwide. Current scientific evidence tends to demonstrate that people with an Asian phenotype have a lower glucose tolerance compared to Caucasian phenotype. In addition, in Caucasian population, consumption of products with a high content of Slowly Digestible Starch (SDS) significantly decreases postprandial glycemic and insulinemic responses compared to products with a low-SDS content. The aim of this study was to evaluate the effect of consuming products with varying levels of SDS on postprandial glycemic and insulinemic responses, both in Asian and Caucasian populations.
Materials and methods
Five products with varying starch digestibility profiles (determined by the SDS method developed by Englyst) and one glucose solution were tested. A randomized cross-over controlled study was set up in the University of Sydney to study the products’ Glycemic and Insulinemic Indexes (GI and II) and postprandial responses over 2 hours. 12 Caucasian and 12 Asian participants were recruited and consumed 50 g of available carbohydrates from each product (norm ISO-26642(2010)).
Asian participants were 28.0 ± 2.6 yo with a body mass index (BMI) of 21.4 ± 0.3 kg/m2 and Caucasians were 26.0 ± 1.1 yo with a BMI of 22.4 ± 0.5 kg/m2 (no difference between groups). Among the products tested, 3 had a high-SDS content (26 to 28 g SDS / 100g) and 2 had a low-SDS content (0 to 2 g SDS / 100g). GI values for Asian participants ranged between 44 and 54 for high-SDS products (low GI) and were medium (64) or high (90) for low-SDS products. GI values for Caucasian participants ranged between 40 and 48 for high-SDS products (low GI) and between 60 and 79 for low-SDS products. In a statistical model including product effect, ethnicity effect, session effect, and the interaction term product*ethnicity, the product effect was the only significant parameter and products were split according to their SDS content. Furthermore, products with a high-SDS content decrease the glycemic peak value by about 1 mM, both in Asian and Caucasian participants. Consumption of high-SDS products also decreases the insulin demand by 29% and 32% in Asians and Caucasians respectively compared to low-SDS products.
Our study demonstrates that consumption of products with a high-SDS content similarly decreases the glycemic and insulinemic responses in both Asian and Caucasian participants. This decrease may be beneficial in the long term to prevent metabolic diseases.
Dietary fibers (DF) have been classified mainly according to their physico-chemical and fermentability properties but it remains unclear whether such classification is relevant when addressing their health effects. Indeed, the nature of physiological effects induced by DF, particularly through their interaction with gut microbiota, remains poorly known due to their diversity, to gut microbiota inter-subjects variability and to the lack of validated non-invasive biomarkers to characterize DF-gut microbiota interaction. The aim of this pilot study was 1) to follow the metabolic fate of 13C-labeled DF through the assessment of 13C-labelled gut-derived metabolites in excreted breath and 2) to evaluate novel non-invasive breath-derived biomarkers of DF-gut microbiota interactions.
Materials and methods
Six healthy women (29.7 ± 1.7 years old, BMI: 23.2 ± 0.9kg/m2, fiber intake: 23 ± 1g/d) consumed in research settings a controlled breakfast containing eight 13C-labelled wheat bran biscuits (50 g of labelled wheat bran, 3.0At%13C). 13C-labelled wheat bran was obtained from wheat cultivated under 13CO2 enriched atmosphere. Samples of expired gases were collected during 24 h after ingestion in order to measure H2 and CH4 by gas chromatography (GC) with piezoelectric detection and 13CO2 and 13CH4 by gas chromatography coupled with an isotope ratio mass spectrometer (GC-IRMS). Apart test breakfast, subjects only consumed standardized meals without fibers.
The analysis of H2 and CH4 24h-kinetic measurements distinguished 2 groups in terms of fermentation related gas excretion: the high-CH4 producers with high baseline CH4 concentrations (42.1 ± 13.7ppm) and low baseline H2 concentrations (7.3 ± 5.8ppm) and the low-CH4 producers with low baseline CH4 concentrations (6.5 ± 3.6ppm) and high baseline H2 concentrations (20.8 ± 16.0ppm). Following the 13C-wheat bran biscuits’ ingestion, postprandial H2 and CH4 concentrations increased more significantly in the high-CH4 producer subjects. 13C enrichment was detectable in expired gases in all subjects. 13CO2 kinetics were similar for all subjects and correspond to the oxidation of the digestible part of the bran. The appearance of 13CH4 was significantly enhanced and prolonged after 180 min in high-CH4 producers compared to low-CH4 producers, suggesting distinct fiber fermentation profile.
This pilot study allowed to consider novel procedures for development of non-invasive breath biomarkers of fiber-gut microbiota interactions. Assessment of expired gas excretion following 13C-labelled fiber ingestion allowed deciphering distinct fermentation profiles: high-CH4 producers vs low-CH4 producers and accordingly provide a related non-invasive breath metabolic signature of the fiber fermentation for each profile. Further gut microbiota and 13C-metabolites analysis will permit to relate the gut bacteria composition with breath gas excretion kinetics according to fiber fermentation profile.
In the broad literature on the effects of ingredients, foods and diets on appetite and energy intake (EI), most trials involve a single acute intervention. It is unclear whether these acute results are generally sustained over longer periods. Researchers and regulators therefore lack an objective basis to judge the appropriate duration of efficacy trials in appetite control, to have confidence that acute effects are likely to be maintained. This gap creates uncertainty in requirements and study designs for the substantiation of satiety-enhancing approaches to help in controlling eating behaviour.
Materials and Methods:
A systematic search of literature (Prospero registration number CRD42015023686) identified studies testing both the acute and chronic effects of food-based interventions aimed at reducing appetite or EI. From 9680 unique records identified from titles and abstracts, 178 papers were selected for full screening. Twenty-six trials met the inclusion criteria and provided data sufficient for use in this analysis, and were also scored for risk of bias (RoB) indicators.
Most of these trials (21/26) measured appetite outcomes and over half (14/26) had objective measures of EI. A significant acute effect of the intervention was retained in 10 of 12 trials for appetite outcomes, and six of nine studies for EI. Initial effects were most likely retained where these were more robust and studies adequately powered. Where the initial, acute effect was not statistically significant, a significant effect was later observed in only two of nine studies for appetite and none of five studies for EI. The main sources of RoB were lack of a priori power calculations and failure to report analyses based on intention-to-treat. Furthermore, 12/26 studies were not adequately powered to detect a meaningful reduction in appetite (~10%).
Maintenance of acute intervention effects on appetite or EI need to be confirmed, but seems likely where the initially observed effects are robust and replicable in adequately powered studies.
The importance of chronic low-grade inflammation in the pathology of numerous age-related chronic conditions is now clear. An unresolved inflammatory response is likely to be involved from the early stages of disease development. The present position paper is the most recent in a series produced by the International Life Sciences Institute's European Branch (ILSI Europe). It is co-authored by the speakers from a 2013 workshop led by the Obesity and Diabetes Task Force entitled ‘Low-grade inflammation, a high-grade challenge: biomarkers and modulation by dietary strategies’. The latest research in the areas of acute and chronic inflammation and cardiometabolic, gut and cognitive health is presented along with the cellular and molecular mechanisms underlying inflammation–health/disease associations. The evidence relating diet composition and early-life nutrition to inflammatory status is reviewed. Human epidemiological and intervention data are thus far heavily reliant on the measurement of inflammatory markers in the circulation, and in particular cytokines in the fasting state, which are recognised as an insensitive and highly variable index of tissue inflammation. Potential novel kinetic and integrated approaches to capture inflammatory status in humans are discussed. Such approaches are likely to provide a more discriminating means of quantifying inflammation–health/disease associations, and the ability of diet to positively modulate inflammation and provide the much needed evidence to develop research portfolios that will inform new product development and associated health claims.
Cereal products exhibit a wide range of glycaemic indexes (GI), but the interaction of their different nutrients and starch digestibility on blood glucose response is not well known. The objective of this analysis was to evaluate how cereal product characteristics can contribute to GI and insulinaemic index and to the parameters describing glycaemic or insulinaemic responses (incremental AUC, maximum concentration and Δpeak). Moreover, interactions between the different cereal products characteristics and glycaemic response parameters were assessed for the first time. Relationships between the cereal products characteristics and the glycaemic response were analysed by partial least square regressions, followed by modelling. A database including 190 cereal products tested by the usual GI methodology was used. The model on glycaemic responses showed that slowly digestible starch (SDS), rapidly digestible starch (RDS) and fat and fibres, and several interactions involving them, significantly explain GI by 53 % and Δpeak of glycaemia by 60 %. Fat and fibres had important contributions to glycaemic response at low and medium SDS contents in cereal products, but this effect disappears at high SDS levels. We showed also for the first time that glycaemic response parameters are dependent on interactions between starch digestibility (interaction between SDS and RDS) and nutritional composition (interaction between fat and fibres) of the cereal products. We also demonstrated the non-linear effect of fat and fibres (significant effect of their quadratic terms). Hence, optimising both the formula and the manufacturing process of cereal products can improve glucose metabolism, which is recognised as strongly influential on human health.
Low glycaemic index (LGI) foods have been proposed as potential means to decrease postprandial glucose excursions and thus to improve diabetes management. We modulated glucose availability of cereal products and thus their glycaemic index to study the metabolic effect of LGI foods on daylong glucose control acutely and in the long term following a 5-week GI intervention diet in free-living subjects. In this randomised, parallel trial, two groups of nineteen overweight subjects followed an ad libitum 5-week intervention diet in which usual starch was replaced by either LGI or high GI (HGI) starch. During the exploration days (days 1 and 36), subjects ate their assigned 13C-labelled test breakfast (LGI or HGI), and total and exogenous glucose kinetics (using stable isotopes), postprandial concentrations of glucose, insulin, lipid profile and nutrient oxidation were assessed after the test breakfast and a standardised lunch. At day 1, LGI breakfast significantly decreased post-breakfast glycaemic response with a parallel decrease in exogenous and total glucose appearance (P < 0·05). Post-lunch and post-breakfast glycaemic responses were positively correlated (r 0·79, P < 0·0001). Following the 5-week diet, difference between the groups in terms of glucose kinetics and response was maintained (no significant interaction group × time) but tended to decrease over time for the post-breakfast glycaemic response. Post-lunch and post-breakfast glycaemic responses remained positively correlated (r 0·47, P = 0·004). Modulation of postprandial glucose availability at breakfast decreased plasma exogenous glucose appearance and improved glucose control at the subsequent lunch. After 5 weeks, these effects were maintained in healthy subjects but remained to be confirmed in the longer term.
The glycaemic index (GI) has been developed in order to classify food according to the postprandial glycaemic response. This parameter is of interest, especially for people prone to glucose intolerance; however, the effects of a low-GI (LGI) diet on body weight, carbohydrate and lipid metabolism remain controversial. We studied the effects of either a LGI or high-GI (HGI) diet on weight control and cardiovascular risk factors in overweight, non-diabetic subjects. The study was a randomized 5-week intervention trial. The thirty-eight subjects (BMI 27·3 (sem 0·2) kg/m2) followed an intervention diet in which usual starch was replaced ad libitum with either LGI or HGI starch. Mean body weight decrease was significant in the LGI group ( − 1·1 (sEM 0·3) kg, P = 0·004) and was significantly greater than in the HGI group ( − 0·3 (sEM 0·2) kg, P = 0·04 between groups). Hunger sensation scales showed a trend towards a decrease in hunger sensation before lunch and dinner in the LGI group when compared with the HGI group (P = 0·09). No significant increase in insulin sensitivity was noticed. The LGI diet also decreased total cholesterol by 9·6 % (P < 0·001), LDL-cholesterol by 8·6 % (P = 0·01) and both LDL-:HDL-cholesterol ratio (10·1 %, P = 0·003) and total:HDL-cholesterol ratio (8·5 %, P = 0·001) while no significant changes were observed in the HGI group. Lowering the GI of daily meals with simple dietary recommendations results in increased weight loss and improved lipid profile and is relatively easy to implement with few constraints. These potential benefits of consuming a LGI diet can be useful to develop practical dietetic advice.
Elucidating the role of carbohydrate quality in human nutrition requires a greater understanding of how the physico-chemical characteristics of foods relate to their physiological properties. It was hypothesised that rapidly available glucose (RAG) and slowly available glucose (SAG), in vitro measures describing the rate of glucose release from foods, are the main determinants of glycaemic index (GI) and insulinaemic index (II) for cereal products. Twenty-three products (five breakfast cereals, six bakery products and crackers, and twelve biscuits) had their GI and II values determined, and were characterised by their fat, protein, starch and sugar contents, with the carbohydrate fraction further divided into total fructose, RAG, SAG and resistant starch. Relationships between these characteristics and GI and II values were investigated by regression analysis. The cereal products had a range of GI (28–93) and II (61–115) values, which were positively correlated (r2 0·22, P<0·001). The biscuit group, which had the highest SAG content (8·6 (sd 3·7) g per portion) due to the presence of ungelatinised starch, was found to have the lowest GI value (51 (sd 14)). There was no significant association between GI and either starch or sugar, while RAG was positively (r2 0·54, P<0·001) and SAG was negatively (r2 0·63, P<0·001) correlated with GI. Fat was correlated with GI (r2 0·52, P<0·001), and combined SAG and fat accounted for 73·1 % of the variance in GI, with SAG as the dominant variable. RAG and protein together contributed equally in accounting for 45·0 % of the variance in II. In conclusion, the GI and II values of the cereal products investigated can be explained by the RAG and SAG contents. A high SAG content identifies low-GI foods that are rich in slowly released carbohydrates for which health benefits have been proposed.
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