Impact of whole cereals and processing on type 2 diabetes mellitus: a review

Potential roles of cereal bioactive compounds in the prevention and treatment of type 2 diabetes: A review of the current knowledge

Diabetes is one of the most common non-communicable diseases in both developed and underdeveloped countries with a 9.3% prevalence. Unhealthy diets and sedentary lifestyles are among the most common reasons for type 2 diabetes mellitus (T2DM). Diet plays a crucial role in both the etiology and treatment of T2DM. There are several recommendations regarding the carbohydrate intake of patients with T2DM. One of them is about reducing the total carbohydrate intake and/or changing the type of carbohydrate to reduce the glycaemic index. Cereals are good sources of carbohydrates in the diet with a significant amount of soluble and non-soluble fiber content. Apart from fiber, it has been shown that the bioactive compounds present in cereals such as proteins, phenolic compounds, carotenoids, and tocols have beneficial impacts in the prevention and treatment of T2DM. Moreover, cereal by-products especially the by-products of milling processes, which are bran and germ, have been reported to have anti-diabetic activities mainly because of their fiber and polyphenols content. Considering the potential functions of cereals in patients with T2DM, this review focuses on the roles of cereal bioactive compounds in the prevention and treatment of type 2 diabetes.

Research Progress of α-Glucosidase Inhibitors Produced by Microorganisms and Their Applications

Based on the easy cultivation of microorganisms and their short cycle time, research on α-glucosidase inhibitors (α-GIs) of microbial origin is receiving extensive attention. Raw materials used in food production, such as cereals, dairy products, fruits, and vegetables, contain various bioactive components, like flavonoids, polyphenols, and alkaloids. Fermentation with specific bacterial strains enhances the nutritional value of these raw materials and enables the creation of hypoglycemic products rich in diverse active ingredients. Additionally, conventional food processing often results in significant byproduct generation, causing resource wastage and environmental issues. However, using bacterial strains to ferment these byproducts into α-GIs presents an innovative solution. This review describes the microbial-derived α-GIs that have been identified. Moreover, the production of α-GIs using industrial food raw materials and processing byproducts as a medium in fermentation is summarized. It is worth analyzing the selection of strains and raw materials, the separation and identification of key compounds, and fermentation broth research methods. Notably, the innovative ideas in this field are described as well. This review will provide theoretical guidance for the development of microbial-derived hypoglycemic foods.

Superfoods for Type 2 Diabetes: A Narrative Review and Proposal for New International Recommendations

Background and Objectives: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease affecting an estimated 537 million individuals worldwide. 'Superfoods' can be integrated into the diet of T2DM patients due to their health benefits. Study Objectives: (i) To carry out a narrative review of 'superfoods' with the potential to reduce glycaemic levels in T2DM patients (2019 to 2022), (ii) to identify 'superfoods' with the potential to reduce HbA1c and (iii) to propose new guidance on the use of 'superfoods'. Materials and Methods: A narrative review was carried out using the databases PubMed, SciELO, DOAJ and Google Scholar. The keywords were ["type 2 diabetes" and ("food" or "diet" or "nutrition") and ("glycaemia" or "glycemia")]. Only review studies were included. Results: Thirty reviews were selected. The 'superfoods' identified as having a potential impact on glycaemic control were foods with polyphenols (e.g., berries), fermented dairy products, whole cereals/grains, nuts and proteins, among others. The possibility of an extensive reduction in Hb1Ac was reported for fermented dairy products, especially yoghurts enriched with vitamin D or probiotics (HbA1c reduction of around 1%) or by increasing the fibre intake by 15 g (or up to 35 g) (HbA1c reduction of around 2%). Conclusion: It is recommended that the identified 'superfoods' are included in the diet of T2DM patients, although this should not substitute an appropriate diet and exercise plan. In particular, yoghurts and an increased fibre intake (by 15 g or up to 35 g) can be used as nutraceuticals. New recommendations on the introduction of 'superfoods' in the diet of T2DM patients have been proposed.

Milling of buckwheat hull to cell-scale: Influences on the behaviors of protein and starch in dough and noodles

Superfine grinding of insoluble dietary fiber (IDF) is a promising method to improve the product quality by regulating the interaction between protein and starch. In this study, the effects of buckwheat-hull IDF powder, at cell-scale (50-10 μm) and tissue-scale (500-100 μm), on the dough rheology and noodle quality were investigated. Results showed that cell-scale IDF with higher exposure of active groups increased the viscoelasticity and deformation resistance of the dough, due to the aggregation of protein-protein and protein-IDF. Compared with the control sample, the addition of tissue-scale or cell-scale IDF significantly increased the starch gelatinization rate (β, C3-C2) and decreased the starch hot-gel stability. Cell-scale IDF increased the rigid structure (β-sheet) of protein, thus improving the noodle texture. The decreased cooking quality of cell-scale IDF-fortified noodles was related to the poor stability of rigid gluten matrix and the weakened interaction between water and macromolecules (starch and protein) during cooking.

Effects of highland barley β-glucan on blood glucose and gut microbiota in streptozotocin-induced, diabetic, C57BL/6 mice on a high-fat diet

OBJECTIVES

This study aimed to investigate the hypoglycemic effect of highland barley β-glucan (HBG) on mice with type 2 diabetes (T2D), and determine whether the hypoglycemic effects are related to modulations of the gut microbiota.

METHODS

T2D was induced with a high-fat diet and streptozotocin in the mice. HBG was orally administered to mice with T2D for 4 wk, and biochemical indices were analyzed in the serum and liver. Fecal samples were collected and analyzed with high-throughput 16S ribosomal RNA sequencing.

RESULTS

Intake of HBG for 4 wk suppressed the body weight, as well as liver and heart indices, and regulated the levels of fasting blood glucose, serum insulin, blood lipid, oxidative damage, and inflammatory reaction in mice with T2D. Furthermore, HBG reversed the gut microbiota dysbiosis in mice with T2D by increasing the abundance of Lachnospiraceae_UCG-006, Streptococcaceae, and Eggerthellaceae, and by decreasing the abundance of Parasutterella.

CONCLUSIONS

Our findings indicate that the antidiabetic abilities of HBG might be related to the improvement of gut microbiota imbalance.

Culinary strategies to manage glycemic response in people with type 2 diabetes: A narrative review

Diet plays a critical role in the management of many chronic diseases. It is well known that individuals with type 2 diabetes (T2D) need to pay close attention to foods rich in carbohydrates to better manage their blood sugar. Usually, individuals are told to increase their dietary fiber intake which is associated with better glycemic control and limit their overall carbohydrate consumption. However, there are many other cooking strategies available to reduce the glycemic response to meals rich in carbohydrates and with a high glycemic index, such as adding fats, proteins, or vinegar, modifying the cooking or preparation processes, and even the selection and storage of foods consumed. The aim of the present narrative review is to summarize some of these existing strategies applied to the cooking process and their ability to modulate glycemic response to meals in individuals with T2D.

Competing paradigms of obesity pathogenesis: energy balance versus carbohydrate-insulin models

The obesity pandemic continues unabated despite a persistent public health campaign to decrease energy intake (“eat less”) and increase energy expenditure (“move more”). One explanation for this failure is that the current approach, based on the notion of energy balance, has not been adequately embraced by the public. Another possibility is that this approach rests on an erroneous paradigm. A new formulation of the energy balance model (EBM), like prior versions, considers overeating (energy intake > expenditure) the primary cause of obesity, incorporating an emphasis on “complex endocrine, metabolic, and nervous system signals” that control food intake below conscious level. This model attributes rising obesity prevalence to inexpensive, convenient, energy-dense, “ultra-processed” foods high in fat and sugar. An alternative view, the carbohydrate-insulin model (CIM), proposes that hormonal responses to highly processed carbohydrates shift energy partitioning toward deposition in adipose tissue, leaving fewer calories available for the body’s metabolic needs. Thus, increasing adiposity causes overeating to compensate for the sequestered calories. Here, we highlight robust contrasts in how the EBM and CIM view obesity pathophysiology and consider deficiencies in the EBM that impede paradigm testing and refinement. Rectifying these deficiencies should assume priority, as a constructive paradigm clash is needed to resolve long-standing scientific controversies and inform the design of new models to guide prevention and treatment. Nevertheless, public health action need not await resolution of this debate, as both models target processed carbohydrates as major drivers of obesity.

Effects of Oats, Tartary Buckwheat, and Foxtail Millet Supplementation on Lipid Metabolism, Oxido-Inflammatory Responses, Gut Microbiota, and Colonic SCFA Composition in High-Fat Diet Fed Rats

Coarse cereals rich in polyphenols, dietary fiber, and other functional components exert multiple health benefits. We investigated the effects of cooked oats, tartary buckwheat, and foxtail millet on lipid profile, oxido-inflammatory responses, gut microbiota, and colonic short-chain fatty acids composition in high-fat diet (HFD) fed rats. Rats were fed with a basal diet, HFD, oats diet (22% oat in HFD), tartary buckwheat diet (22% tartary buckwheat in HFD), and foxtail millet diet (22% foxtail millet in HFD) for 12 weeks. Results demonstrated that oats and tartary buckwheat attenuated oxidative stress and inflammatory responses in serum, and significantly increased the relative abundance of Lactobacillus and Romboutsia in colonic digesta. Spearman’s correlation analysis revealed that the changed bacteria were strongly correlated with oxidative stress and inflammation-related parameters. The concentration of the butyrate level was elevated by 2.16-fold after oats supplementation. In addition, oats and tartary buckwheat significantly downregulated the expression of sterol regulatory element-binding protein 2 and peroxisome proliferator-activated receptors γ in liver tissue. In summary, our results suggested that oats and tartary buckwheat could modulate gut microbiota composition, improve lipid metabolism, and decrease oxidative stress and inflammatory responses in HFD fed rats. The present work could provide scientific evidence for developing coarse cereals-based functional food for preventing hyperlipidemia.

Potential of Indonesian Community Food Sources which are Rich in Fiber as an Alternative Staple Food for Type 2 Diabetics: A Scoping Review

BACKGROUND: Staple foods as a source of carbohydrates contribute most of human energy needs. Based on Perkeni’s recommendation, diabetic patients can consume at least 45–60% of carbohydrate sources. In addition, several previous studies have shown that increasing the adequacy of dietary fiber above 20–25 g/day can improve glycemic control. AIM: Our scoping review investigated the potential of Indonesian food sources, namely, sorghum and corn as a source of carbohydrates and also fiber as a substitute rice for diabetic patients. METHODS: We systematically used electronic databases searched such as PubMed, Science Direct, Web of Science, Portal Garuda, Sinta Ristekbrin, and Google Scholar. We choose the relevant documents used experimental animals and humans’ studies then published between 2011 and 2021. RESULTS: In total, 17 relevant articles discuss the relationship between giving corn or sorghum with blood glucose levels of animal studies and human. Some studies showed that the effect of eating sorghum or its derivatives can reduce blood glucose. As well as, the other articles indicated eating corn or its derivatives also decrease glycemic response of healthy people and experimental animals. Corn and sorghum contain dietary fiber in the form of resistant starch and have low glycemic index compare with white rice. Furthermore, corn also contains essential fat, mineral, β-Carotene, and isoflavone, while sorghum also includes phenolic components such as phenolic acids and flavonoids. CONCLUSIONS: Sorghum and corn have the potential as an alternative staple food to achieve a better glycemic response in diabetic patients.

Nutrition transition and chronic diseases in China (1990-2019): industrially processed and animal calories rather than nutrients and total calories as potential determinants of the health impact

OBJECTIVE

To extend analyses of nutrition transition in developed countries to China within the framework of the 3Vs rule considering degree of processing starting with plant/animal calorie ratio (Rule 1), industrially processed foods (IPFs, Rule 2), and food diversity through nutrient intakes (Rule 3).

DESIGN

Total and main food group (n 13) calorie intakes, percentages of animal and IPF calories, adequacy of the Dietary Reference Intake (DRI) and prevalence of chronic diseases were retrieved from scientific literature and international databases.

SETTING

China, 1990–2019.

PARTICIPANTS

Overall population.

RESULTS

The total calorie intake decreased by 9 % over 30 years while the prevalence of chronic diseases substantially increased. Percentages of IPFs (Rule 1) and animal (Rule 2) calorie intake shifted from 9 to 30 % and 2 to 30 %, respectively. Meanwhile, the overall DRI adequacy (Rule 3) did not improve, with calcium and retinol deficiencies in 2019, and, although remaining above DRI, iron, copper, magnesium, and vitamins E, C and B1–B9 intakes regularly decreased. Notably, the prevalence of obesity increased five-fold, paralleling the exponential increase in IPF calorie intake. Both sources of calories were highly correlated with prevalence of main chronic diseases.

CONCLUSIONS

Despite a slight decreased of total calorie consumption and small variations of adequacy with DRI, the farther the Chinese population moved away from the 3Vs rule during the 1990–2019 period, the more the prevalence of chronic diseases increased. Further analyses on foods’ transitions will be better assessed when advocating sources/quality of calories (Rules 1/2), rather than only nutrient composition (Rule 3).

Oat-Based Foods: Chemical Constituents, Glycemic Index, and the Effect of Processing

The desire for foods with lower glycemic indices has led to the exploration of functional ingredients and novel food processing techniques. The glycemic index (GI) is a well-recognized tool to assess the capacity of foods to raise blood glucose levels. Among cereal crops, oats have shown the greatest promise for mitigating glycemic response. This review evaluated decades of research on the effects of oat components on the GI level of oat-based foods with specific emphasis on oat starch, β-glucans, proteins, and phenolics. The effects of commonly used processing techniques in oats on GI level, including heating, cooling, and germination were also discussed. In addition, the GI of oat-based foods in various physical formats such as whole grain, flakes, and flour was systematically summarized. The aim of this review was to synthesize knowledge of the field and to provide a deeper understanding of how the chemical composition and processing of oats affect GI, thereby further benefiting the development of low-GI oat foods.

Inhibition of in vitro enzymatic starch digestion by coffee extract

There is evidence that moderate coffee consumption is beneficial in the prevention of type 2 diabetes, however, the underlying mechanism is not understood. In this study, the effects of an extract of ground coffee on the in vitro enzymatic digestion of starch were investigated. The coffee extract decreased the rate and extent of starch digestion, with kinetic analysis showing that the extract reduced the binding affinity of the enzymes for the substrate and their catalytic turnover. Fluorescence quenching indicated that the coffee extract formed complexes with the digestive enzymes through a static quenching mechanism. Ultraviolet absorption and circular dichroism spectra of the digestive enzymes confirmed that the coffee extract decreased the proportion of β-sheet structures in the enzymes. Therefore, we conclude that compounds in the soluble coffee extract can interact with porcine pancreatic amylase and amyloglucosidase causing inhibition of the enzymes and decreasing in vitro starch digestion.

Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

Grains are important sources of carbohydrates in global dietary patterns. The majority of these carbohydrates, especially in refined-grain products, are digestible. Most carbohydrate digestion takes place in the small intestine where monosaccharides (predominantly glucose) are absorbed, delivering energy to the body. However, a considerable part of the carbohydrates, especially in whole grains, is indigestible dietary fibers. These impact gut motility and transit and are useful substrates for the gut microbiota affecting its composition and quality. For the most part, the profile of digestible and indigestible carbohydrates and their complexity determine the nutritional quality of carbohydrates. Whole grains are more complex than refined grains and are promoted as part of a healthy and sustainable diet mainly because the contribution of indigestible carbohydrates, and their co-passenger nutrients, is significantly higher. Higher consumption of whole grain is recommended because it is associated with lower incidence of, and mortality from, CVD, type 2 diabetes, and some cancers. This may be due in part to effects on the gut microbiota. Although processing of cereals during milling and food manufacturing is necessary to make them edible, it also offers the opportunity to still further improve the nutritional quality of whole-grain flours and foods made from them. Changing the composition and availability of grain carbohydrates and phytochemicals during processing may positively affect the gut microbiota and improve health.

Deep Dive Into the Effects of Food Processing on Limiting Starch Digestibility and Lowering the Glycemic Response

During processing of cereal-based food products, starch undergoes dramatic changes. The objective of this work was to evaluate the impact of food processing on the starch digestibility profile of cereal-based foods using advanced imaging techniques, and to determine the effect of preserving starch in its native, slowly digestible form on its in vivo metabolic fate. Four different food products using different processing technologies were evaluated: extruded products, rusks, soft-baked cakes, and rotary-molded biscuits. Imaging techniques (X-ray diffraction, micro-X-ray microtomography, and electronic microscopy) were used to investigate changes in slowly digestible starch (SDS) structure that occurred during these different food processing technologies. For in vivo evaluation, International Standards for glycemic index (GI) methodology were applied on 12 healthy subjects. Rotary molding preserved starch in its intact form and resulted in the highest SDS content (28 g/100 g) and a significantly lower glycemic and insulinemic response, while the three other technologies resulted in SDS contents below 3 g/100 g. These low SDS values were due to greater disruption of the starch structure, which translated to a shift from a crystalline structure to an amorphous one. Modulation of postprandial glycemia, through starch digestibility modulation, is a meaningful target for the prevention of metabolic diseases.

Evaluation of the efficacy of toasted white and tannin sorghum flours to improve oxidative stress and lipid profile in vivo

The objective of the present work was to evaluate and compare the effect of toasted white and tannin sorghum flours on lipid metabolism and antioxidant potential in vivo. Male spontaneously hypertensive rats (SHR) were induced to oxidative stress with paracetamol and fed a normal diet (AIN-93M) and diets containing toasted tannin sorghum flour and toasted white sorghum flour (without tannins), replacing 100% cellulose, during 29 days. Hepatotoxicity was assessed by biochemical tests and by quantifying oxidative stress markers. Groups that received toasted sorghum flour with and without tannins showed reduction of alanine aminotransferase (ALT) concentration and improvement of lipid profile, with increase of high-density lipoprotein (HDL) compared to paracetamol control, and did not differ statistically from the AIN-93M control. Moreover, toasted white sorghum flour presented similar efficacy in reducing oxidative stress in liver tissue compared to toasted tannin sorghum flour, although the former had lower total phenolic content and antioxidant capacity, suggesting a greater effect of small phenolic compounds, such as phenolic acids, in the prevention of oxidative stress. Therefore, toasted white and tannin sorghum flours had similar efficacy to improve the lipid profile and oxidative stress in rats treated with paracetamol, constituting potential sources of antioxidants, which can be used as promising ready-to-eat foods and as ingredients for the development of sorghum-based products. PRACTICAL APPLICATION: The health benefits of sorghum coupled with the growing interest of the food industry in producing healthier food products have motivated the development of toasted sorghum flours as potential sources of antioxidants and dietary fiber. We have demonstrated that consumption of toasted white and tannin sorghum flours by rats treated with paracetamol had similar efficacy to improve oxidative stress and lipid profile. Thus, these toasted sorghum flours have great potential to be used by the food industry as ready-to-eat foods or as ingredients in the development of various food products.

IRS-1/PI3K/Akt pathway and miRNAs are involved in whole grain highland barley (Hordeum vulgareL.) ameliorating hyperglycemia of db/db mice

The present investigation further unravels the underlying molecular mechanism of WGH on T2DM: IRS-1/PI3K/Akt pathway and related miRNA expression.