Substitution of Refined Conventional Wheat Flour with Wheat High in Resistant Starch Modulates the Intestinal Microbiota and Fecal Metabolites in Healthy Adults: A Randomized, Controlled Trial

Swapping White for High-Fibre Bread Increases Faecal Abundance of Short-Chain Fatty Acid-Producing Bacteria and Microbiome Diversity: A Randomized, Controlled, Decentralized Trial

A low-fibre diet leads to gut microbiota imbalance, characterized by low diversity and reduced ability to produce beneficial metabolites, such as short-chain fatty acids (SCFAs). This imbalance is associated with poor gastrointestinal and metabolic health. We aimed to determine whether one dietary change, substitution of white bread with high-fibre bread, improves gut microbiota diversity and SCFA-producing capability. Twenty-two healthy adults completed a two-phase randomized, cross-over trial. The participants consumed three slices of a high-fibre bread (Prebiotic Cape Seed Loaf with BARLEYmax®) or control white bread as part of their usual diet for 2 weeks, with the treatment periods separated by a 4-week washout. High-fibre bread consumption increased total dietary fibre intake to 40 g/d, which was double the amount of fibre consumed at baseline or during the white bread intervention. Compared to white bread, the high-fibre bread intervention resulted in higher faecal alpha diversity (Shannon, p = 0.014) and relative abundance of the Lachnospiracae ND3007 group (p < 0.001, FDR = 0.019) and tended to increase the butyrate-producing capability (p = 0.062). In conclusion, substituting white bread with a high-fibre bread improved the diversity of gut microbiota and specific microbes involved in SCFA production and may enhance the butyrate-producing capability of gut microbiota in healthy adults. These findings suggest that a single dietary change involving high-fibre bread provides a practical way for adults to exceed recommended dietary fibre intake levels that improve gut microbiota composition and support gastrointestinal and metabolic health.

Altering structure and enzymatic resistance of high-amylose maize starch by irradiative depolymerization and annealing with palmitic acid as V-type inclusion compound

This study explored a new physical modification approach to regulate enzymatic resistance of high-amylose starch for potentially better nutritional outcomes. High-amylose maize starch (HAMS) was subjected to chain depolymerization by electron beam irradiation (EBI), followed by inducing ordered structure through annealing in palmitic acid solution (APAS). APAS treatment significantly promotes the formation of ordered structure. Starch after the combinative modification showed up to 5.2 % increase in total crystallinity and up to 1.2 % increase in V-type fraction. The EBI-APAS modification led to increased gelatinization temperature (from 66.1 to 87.6 °C) and reduced final digested percentage under in vitro stimulated digestion conditions. The moderate extent of depolymerization resulted in higher enzymatic resistance, indicating that the extent of depolymerization is crucial in EBI-APAS modification. Pearson analysis showed a significant correlation between gelatinization onset temperature and digestion kinetic parameter (k1, rate constant of fast-phase digestion). Overall, the result suggests that ordered structures of degraded molecules induced by the combinative modification contribute to the enzymatic resistance of starch. This study sheds lights on future applications of EBI-APAS approach to regulate multi-scale structures and nutritional values of high-amylose starch.

Grain Intake and Cardiometabolic Health-Towards Precision Nutrition

Grains are widely consumed all over the world, providing calories, macronutrients, micronutrients, dietary fiber, minerals, and plenty of phytochemicals [...].

Dietary Fiber and Its Potential Role in Obesity: A Focus on Modulating the Gut Microbiota

Dietary fiber is a carbohydrate polymer with ten or more monomeric units that are resistant to digestion by human digestive enzymes, and it has gained widespread attention due to its significant role in health improvement through regulating gut microbiota. In this review, we summarized the interaction between dietary fiber, gut microbiota, and obesity, and the beneficial effects of dietary fiber on obesity through the modulation of microbiota, such as modifying selective microbial composition, producing starch-degrading enzymes, improving gut barrier function, reducing the inflammatory response, reducing trimethylamine N-oxide, and promoting the production of gut microbial metabolites (e.g., short chain fatty acids, bile acids, ferulic acid, and succinate). In addition, factors affecting the gut microbiota composition and metabolites by dietary fiber (length of the chain, monosaccharide composition, glycosidic bonds) were also concluded. Moreover, strategies for enhancing the biological activity of dietary fiber (fermentation technology, ultrasonic modification, nanotechnology, and microfluidization) were subsequently discussed. This review may provide clues for deeply exploring the structure-activity relationship between dietary fiber and antiobesity properties by targeting specific gut microbiota.

Dietary supplementation with resistant starch contributes to intestinal health

PURPOSE OF REVIEW

Resistant starch has received much attention recently as a healthy carbohydrate component of the diet. Resistant starch is not digested in the small intestine and can thus affect the gut microbiota of the host because of its fermentability. This review summarizes the interactions along the resistant starch-gut microbiota-host axis to help understand the health effects of resistant starch.

RECENT FINDINGS

Recent studies indicate that resistant starch can be a helpful dietary component for special disease states like diabetes, metabolic syndrome, chronic kidney disease, constipation, and colitis. Its health effects are associated with modulation of the gut microbiota, and with gut microbes converting resistant starch into active and bioavailable metabolites that promote intestinal health.

SUMMARY

The results from human clinical trials and studies in animal models indicate that supplementation of the diet with resistant starch in different metabolic diseases help remodel gut microbiota, especially increasing short-chain fatty acid (SCFA)-producing bacteria, and produce bioactive metabolites like SCFA, bile acids, and amino acids responsible for a variety of health effects. The gut microbiota and microbial metabolites probably mediate the effects of resistant starch on intestinal health.

Meta-analysis reveals gut microbiome and functional pathway alterations in response to resistant starch

Resistant starch (RS) has the ability to improve the structure of the gut microbiota, regulate glucolipid metabolism and maintain the health of the human body, and has been extensively studied by many scholars in recent years. However, previous studies have provided a wide range of results on the differences in the gut microbiota after RS intake. In this article, we performed a meta-analysis of a total of 955 samples of 248 individuals from the seven studies included to compare the gut microbiota of the baseline and the end-point of RS intake. At the end-point, RS intake was related to a lower gut microbial α-diversity and higher relative abundance of Ruminococcus, Agathobacter, Faecalibacterium and Bifidobacterium, and the functional pathways of the gut microbiota related to the carbohydrate metabolism, lipid metabolism, amino acid metabolism and genetic information processing were higher. Different types of resistant starch and different populations led to varied responses on the gut microbiome. The altered gut microbiome may contribute to improve the blood glucose level and insulin resistance, which may be a potential treatment route for diabetes, obesity and other metabolic diseases.

Unlocking the Potential of High-Amylose Starch for Gut Health: Not All Function the Same

High-amylose starch has unique functional properties and nutritional values in food applications. This type of starch is generally resistant to enzymatic digestion in the gastrointestinal tract, and contains an increased fraction of resistant starch (RS), which is a type of dietary fiber. The digestion and fermentation of high-amylose starch in the gut are of current research interest, as the processes are related to its nutritional functionality. This review summarizes recent in vitro and in vivo studies on the digestion and fermentation of high-amylose starches from different botanical sources and those that have been obtained by modifications. The RS content and fermentation properties are compared among high-amylose starches. This review aims to provide a current understanding of the relationship between high-amylose starch structures and fermentation-related nutritional properties. The results of these studies suggest that both modifications and food processing of high-amylose starch result in distinct fermentation products and nutritional properties. The review provides insight into the potential future applications of diverse high-amylose starches as bioactive compounds to modulate colonic fermentation.

High Amylose Wheat Bread at Breakfast Increases Plasma Propionate Concentrations and Reduces the Postprandial Insulin Response to the Following Meal in Overweight Adults

BACKGROUND

High amylose starchy foods modulate the postprandial metabolic response in humans. However, the mechanisms of their metabolic benefits and their impact on the subsequent meal have not been fully elucidated.

OBJECTIVE

We aimed to evaluate whether glucose and insulin responses to a standard lunch are influenced by the consumption of amylose-rich bread at breakfast in overweight adults and whether changes in plasma short chain fatty acids (SCFAs) concentrations contribute to their metabolic effects.

METHODS

Using a randomized crossover design, 11 men and 9 women, BMI 30 ± 3 kg/m², 48 ± 19 y, consumed at breakfast 2 breads made with high amylose flour (HAF): 85%-HAF (180 g) and 75%-HAF (170 g), and control bread (120 g) containing 100% conventional flour. Plasma samples were collected at fasting, 4 h after breakfast, and 2 h after a standard lunch to measure glucose, insulin, and SCFA concentrations. ANOVA posthoc analyses were used for comparisons.

RESULTS

Postprandial plasma glucose responses were 27% and 39% lower after breakfasts with 85%- and 70%-HAF breads than control bread (P = 0.026 and P = 0.003, respectively), with no difference after lunch. Insulin responses were not different between the 3 breakfasts, whereas there was a 28% lower response after the lunch following breakfast with 85%-HAF bread than the control (P = 0.049). Propionate concentrations increased from fasting by 9% and 12% 6 h after breakfasts with 85%- and 70%-HAF breads and decreased by 11% with control bread (P < 0.05). At 6 h after breakfast with 70%-HAF bread, plasma propionate and insulin were inversely correlated (r = -0.566; P = 0.044).

CONCLUSIONS

Amylose-rich bread reduces the postprandial glucose response after breakfast and insulin concentrations after the subsequent lunch in overweight adults. This second meal effect may be mediated by the elevation of plasma propionate due to intestinal fermentation of resistant starch. High amylose products could be a promising tool in a dietary prevention strategy for type 2 diabetes.

THIS TRIAL WAS REGISTERED AT CLINICAL TRIAL REGISTRY AS

NCT03899974 (https://www.

CLINICALTRIALS

gov/ct2/show/NCT03899974).

Naturally cultured high resistant starch rice improved postprandial glucose levels in patients with type 2 diabetes: A randomized, double-blinded, controlled trial

Objective

To assess the effect of a novel naturally cultured rice with high resistant starch (RS) on postprandial glycemia in patients with type 2 diabetes compared to ordinary rice.

Design

This study is a randomized, double-blinded controlled trial.

Methods

Patients with type 2 diabetes were recruited, and postprandial glucose levels were measured at 5-time points after the ingestion of one of two types of cooked rice in random order. Paired t-tests were used to compare postprandial blood glucose changes and increment areas under the blood glucose curve between high-RS rice and ordinary rice.

Results

The increments of the postprandial blood glucose levels for high-RS rice were significantly lower than that for ordinary rice, i.e., 2.80 ± 1.38 mmol/L vs. 3.04 ± 1.50 mmol/L (P = 0.043) and 3.94 ± 2.25 mmol/L vs. 4.25 ± 2.29 mmol/L (P = 0.036) at 30 min and 60 min, respectively. The incremental areas under the blood glucose curve for high-RS rice were also significantly lower than that for ordinary rice, i.e., 42.04 ± 20.65 [mmol/(L·min)] vs. 45.53 ± 22.45 [mmol/(L·min)] (P = 0.043), 143.54 ±69.63 [mmol/(L·min)] vs. 155.15 ± 73.53 [mmol/(L·min)] (P = 0.026), and 354.61 ± 191.96 [mmol/(L·min)] vs. 379.78 ± 195.30 [mmol/(L·min)] (P = 0.042) at 30, 60, and 120 min, respectively. Repeated-measures ANOVA showed that postprandial glucose levels were not affected by the test order.

Conclusion

The novel high-RS rice as a staple food when substituting for widely consumed ordinary rice may provide potential health benefits by lowering blood glucose in patients with type 2 diabetes.

Dietary Fiber Intake and Gut Microbiota in Human Health

Dietary fiber is fermented by the human gut microbiota, producing beneficial microbial metabolites, such as short-chain fatty acids. Over the last few centuries, dietary fiber intake has decreased tremendously, leading to detrimental alternations in the gut microbiota. Such changes in dietary fiber consumption have contributed to the global epidemic of obesity, type 2 diabetes, and other metabolic disorders. The responses of the gut microbiota to the dietary changes are specific to the type, amount, and duration of dietary fiber intake. The intricate interplay between dietary fiber and the gut microbiota may provide clues for optimal intervention strategies for patients with type 2 diabetes and other noncommunicable diseases. In this review, we summarize current evidence regarding dietary fiber intake, gut microbiota modulation, and modification in human health, highlighting the type-specific cutoff thresholds of dietary fiber for gut microbiota and metabolic outcomes.

Prebiotic Potential of Dietary Beans and Pulses and Their Resistant Starch for Aging-Associated Gut and Metabolic Health

Dietary pulses, including dry beans, lentils, chickpeas, and dry peas, have the highest proportion of fiber among different legume cultivars and are inexpensive, easily accessible, and have a long shelf-life. The inclusion of pulses in regular dietary patterns is an easy and effective solution for achieving recommended fiber intake and maintaining a healthier gut and overall health. Dietary pulses-derived resistant starch (RS) is a relatively less explored prebiotic ingredient. Several in vitro and preclinical studies have elucidated the crucial role of RS in fostering and shaping the gut microbiota composition towards homeostasis thereby improving host metabolic health. However, in humans and aged animal models, the effect of only the cereals and tubers derived RS has been studied. In this context, this review collates literature pertaining to the beneficial effects of dietary pulses and their RS on gut microbiome-metabolome signatures in preclinical and clinical studies while contemplating their potential and prospects for better aging-associated gut health. In a nutshell, the incorporation of dietary pulses and their RS in diet fosters the growth of beneficial gut bacteria and significantly enhances the production of short-chain fatty acids in the colon.

Perspective: Utilizing High Amylose Wheat Flour to Increase Dietary Fiber Intake of Children and Adolescents: A Health by Stealth Approach

Children and adolescents have consistently failed to meet recommended levels of dietary fiber consumption, thus making fiber a nutrient of concern. The importance of adequate dietary fiber intake to attain a healthy diet necessitates the identification of fiber-rich and readily consumed food sources by youth. Grain-based foods derived from whole grains represent a strategic initiative to increase dietary fiber consumption and is consistent with the American diet pattern. Increased intake of foods made from whole grains have been positively associated with improved health outcomes but are also less preferred among youth compared to refined grain products, which make up the majority of their carbohydrate intake. Advances in the commercialization and availability of high amylose wheat flour, a source of resistant starch fiber, provides an opportunity to remedy the suggested acceptability issues of whole grain products indicative of sensory factors, without compromising the amount of fiber ingested. Resistant starch fiber consumption has been associated with health benefits including improved blood sugar management, improved markers of digestive and gut health, increased satiety, and a reduced inflammatory response among adults. The limited studies that indicate fiber's direct benefit among youth are largely observational, thereby necessitating the need for more controlled trials for these age groups. Replacing traditional refined wheat flour with refined high amylose wheat flour has the unique ability to increase dietary fiber consumption without compromising desired sensory and finished product characteristics and thus can help increase dietary fiber consumption in children and adolescents who struggle to meet adequate intakes of fiber.