Effects of concentrated arabinoxylan and β-glucan compared with refined wheat and whole grain rye on glucose and appetite in subjects with the metabolic syndrome: a randomized study

The effects of a fibre-enriched bakery product on glucose, insulin values and appetite. A pilot randomised cross-over trial

Brewers spent grain (BSG) is a valuable source of arabinoxylans with potential beneficial effects on glucose values. This pilot randomised crossover double-blind trial compared the effects of panettone, a sweet baked-product, enriched with BSG-fibre (p-rich) to unenriched panettone (p-standard) on glucose and insulin blood values and appetite scores. Ten healthy volunteers consumed each food in a random order. Blood variables and appetite scores were assessed at fasting and at different intervals after each food consumption. Glucose values were significantly higher after p-standard intake at 90-min (89.9 ± 16.1 vs 74.6 ± 19.4 mg/dL) and 120-min (81.1 ± 9.85 vs 72.1 ± 14.0 mg/dL). The areas-under-the-curve (AUCs) were lower for both glucose (p = .043) and insulin values (p = .036) with p-rich. At 240-min, satiety was higher (p = .006), and desire-to-eat lower (p = .008) with p-rich; desire-to-eat AUC was lower with p-rich too (p = .029). The integration of a small amount of BSG-derived fibre into a sweet food led to improved glycaemic control and appetite regulation.

Extraction, purification, structural characteristics, bioactivity and potential applications of polysaccharides from Avena sativa L.: A review

Avena sativa L. (A. sativa L.), commonly known as oat, is a significant cereal grain crop with excellent edible and medicinal value. Oat polysaccharides (OPs), the major bioactive components of A. sativa L., have received considerable attention due to their beneficial bioactivities. However, the isolation and purification methods of OPs lack innovation, and the structure-activity relationship remains unexplored. This review emphatically summarized recent progress in the extraction and purification methods, structural characteristics, biological activities, structure-to-function associations and the potential application status of OPs. Different materials and isolation methods can result in the differences in the structure and bioactivity of OPs. OPs are mainly composed of various monosaccharide constituents, including glucose, arabinose and mannose, along with galactose, xylose and rhamnose in different molar ratios and types of glycosidic bonds. OPs exhibited a broad molecular weight distribution, ranging from 1.34 × 105 Da to 4.1 × 106 Da. Moreover, structure-activity relationships demonstrated that the monosaccharide composition, molecular weight, linkage types, and chemical modifications are closely related to their multiple bioactivities, including immunomodulatory activity, antioxidant effect, anti-inflammatory activity, antitumor effects etc. This work can provide comprehensive knowledge, update information and promising directions for future exploitation and application of OPs as therapeutic agents and multifunctional food additives.

Beneficial glycaemic effects of high-amylose barley bread compared to wheat bread in type 2 diabetes

BACKGROUND

Cereals foods with a high content of dietary fibres or amylose have potential to lower postprandial glucose levels. Optimisation of cereal foods may improve management of type 2 diabetes (T2D).

METHODS

We investigated the impact on 4 h postprandial glucose responses given as incremental area under curve (iAUC) of bread made of either 50% RNAi-based (genetically modified) amylose-only barley flour (AmOn) (and 50% wheat flour), 50% hulless barley flour (and 50% wheat flour) or 75% hulless barley (and 25% wheat flour) in subjects with T2D compared with 100% wheat flour bread.

DESIGN

Twenty adults with T2D were randomly allocated to one of four breads at four separate visits. We measured fasting and 4 h postprandial responses of glucose, insulin, glucagon, triacylglycerol (TG), free fatty acids (FFA), glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP). Mixed model ANOVA was used to examine the differences.

RESULTS

Bread made from 50% AmOn lowered the 4 h postprandial glucose by 34%, 27%, 23% (P < 0.05) compared with 100% wheat, 50% or 75% hulless barley, respectively. Bread made from 75% hulless barley reduced the postprandial glucose response (iAUC) by 11% (P < 0.05) compared to 100% wheat bread. Postprandial insulin responses (iAUC) were reduced for 50% AmOn compared with 100% wheat and 50% hulless barley and for 75% hulless compared to 50% hulless barley bread (P < 0.05). 4 h postprandial glucagon (tAUC) did not differ between the four bread types (P > 0.05). Lower postprandial GIP (iAUC) was observed after all barley breads compared to 100% wheat (P < 0.05), whereas no difference was seen in postprandial GLP-1. Postprandial TG and FFA (tAUC) were difficult to judge due to differences in fasting values.

CONCLUSIONS

Bread made by replacing wheat flour with either 50% high-amylose or 75% hulless barley flour lowered postprandial glucose responses compared to 100% wheat bread indicating a beneficial impact on glucose regulation in T2D subjects. This trial was registered at clinicaltrials.gov as NCT04646746.

Does sourdough bread provide clinically relevant health benefits?

During the last decade, scientific interest in and consumer attention to sourdough fermentation in bread making has increased. On the one hand, this technology may favorably impact product quality, including flavor and shelf-life of bakery products; on the other hand, some cereal components, especially in wheat and rye, which are known to cause adverse reactions in a small subset of the population, can be partially modified or degraded. The latter potentially reduces their harmful effects, but depends strongly on the composition of sourdough microbiota, processing conditions and the resulting acidification. Tolerability, nutritional composition, potential health effects and consumer acceptance of sourdough bread are often suggested to be superior compared to yeast-leavened bread. However, the advantages of sourdough fermentation claimed in many publications rely mostly on data from chemical and in vitro analyzes, which raises questions about the actual impact on human nutrition. This review focuses on grain components, which may cause adverse effects in humans and the effect of sourdough microbiota on their structure, quantity and biological properties. Furthermore, presumed benefits of secondary metabolites and reduction of contaminants are discussed. The benefits claimed deriving from in vitro and in vivo experiments will be evaluated across a broader spectrum in terms of clinically relevant effects on human health. Accordingly, this critical review aims to contribute to a better understanding of the extent to which sourdough bread may result in measurable health benefits in humans.

Acute Effects of Dietary Fiber in Starchy Foods on Glycemic and Insulinemic Responses: A Systematic Review of Randomized Controlled Crossover Trials

Dietary fiber (DF) consumption has been associated with improved glycemic control in epidemiological and long-term interventional studies. However, its acute effects are not yet clear. This systematic review aims to elucidate the postprandial effects of DF in starchy products on glycemia and insulinemia. An electronic search of databases was conducted, and forty-one records met the inclusion criteria and underwent a risk-of-bias assessment. It was shown that soluble DF does not clearly affect glycemia in individuals with normal weight, while resistant starch may be more effective in flattening glycemic responses. Concerning insulinemia, both soluble DF and resistant starch have mixed results, with either favorable or no effects. Data on insoluble DF and glucose metabolism are scarce. The same mixed results for glycemia can be seen in healthy volunteers with overweight/obesity, while resistant starch seems to improve insulinemic responses. Finally, more studies need to examine the acute effects of DF in starchy foods on glucose metabolism and insulin secretion in individuals facing glucose abnormalities. Additionally, more studies are needed to prove whether ingesting high-fiber carbohydrate-containing products per se can result in blunted glycemic and insulinemic responses and which DF type and amount are more effective.

A comparison of the effects of resistant starch types on glycemic response in individuals with type 2 diabetes or prediabetes: A systematic review and meta-analysis

Background

Type 2 diabetes (T2D) diagnoses are predicted to reach 643 million by 2030, increasing incidences of cardiovascular disease and other comorbidities. Rapidly digestible starch elevates postprandial glycemia and impinges glycemic homeostasis, elevating the risk of developing T2D. Starch can escape digestion by endogenous enzymes in the small intestine when protected by intact plant cell walls (resistant starch type 1), when there is a high concentration of amylose (resistant starch type 2) and when the molecule undergoes retrogradation (resistant starch type 3) or chemical modification (resistant starch type 4). Dietary interventions using resistant starch may improve glucose metabolism and insulin sensitivity. However, few studies have explored the differential effects of resistant starch type. This systematic review and meta-analysis aims to compare the effects of the resistant starch from intact plant cell structures (resistant starch type 1) and resistant starch from modified starch molecules (resistant starch types 2-5) on fasting and postprandial glycemia in subjects with T2D and prediabetes.

Methods

Databases (PubMed, SCOPUS, Ovid MEDLINE, Cochrane, and Web of Science) were systematically searched for randomized controlled trials. Standard mean difference (SMD) with 95% confidence intervals (CI) were determined using random-effects models. Sub-group analyses were conducted between subjects with T2D versus prediabetes and types of resistant starch.

Results

The search identified 36 randomized controlled trials (n = 982), 31 of which could be included in the meta-analysis. Resistant starch type 1 and type 2 lowered acute postprandial blood glucose [SMD (95% CI) = -0.54 (-1.0, -0.07)] and [-0.96 (-1.61, -0.31)]. Resistant starch type 2 improved acute postprandial insulin response [-0.71 (-1.31, -0.11)]. In chronic studies, resistant starch type 1 and 2 lowered postprandial glucose [-0.38 (-0.73, -0.02), -0.29 (-0.53, -0.04), respectively] and resistant starch type 2 intake improved fasting glucose [-0.39 (-0.66, -0.13)] and insulin [-0.40 (-0.60, -0.21)].

Conclusion

Resistant starch types 1 and 2 may influence glucose homeostasis via discrete mechanisms, as they appear to influence glycemia differently. Further research into resistant starch types 3, 4, and 5 is required to elucidate their effect on glucose metabolism. The addition of resistant starch as a dietary intervention for those with T2D or prediabetes may prevent further deterioration of glycemic control.

Effects of whole grain intake on glucagon-like peptide 1 and glucose-dependent insulinotropic peptide: a systematic review and meta-analysis

CONTEXT

Whole grain intake may control help glycemia and reduce food intake by affecting the secretion of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP).

OBJECTIVE

This systematic review and meta-analysis aimed to assess the postprandial and long-term effects of whole grains on GLP-1 and GIP levels.

DATA SOURCES

PubMed, Web of Science, and Scopus online databases were searched systematically to identify relevant randomized clinical trials (RCTs) published up to April 2021.

STUDY SELECTION

RCTs that evaluated the effects of whole grains, compared with refined grains, on the postprandial area under the curve (AUC) value, the postprandial serum concentration of incretins from 0 to 180 minutes, or the fasting level of incretins after at least 14 days of intervention were included.

RESULTS

Nineteen studies were included in the meta-analysis. The results showed that acute intake of whole grains could not significantly change the AUC value of GLP-1 or GIP. However, the AUC value of GIP was reduced more significantly in (1) unhealthy participants (standard mean difference [SMD] -1.08; 95%CI, -2.07 to -0.10; I2 = 75.9%) compared with healthy participants, and (2) those with a baseline fasting blood glucose of ≥99 mg/dL (SMD -0.71; 95%CI, -1.30 to -0.11; I2 = 74.4%) compared with those with a baseline value of < 99 mg/dL. On the other hand, the results of time-response evaluation during 0 to 180 minutes after the intake of test meals showed that serum concentrations of GIP decreased significantly from 0 to 30 minutes (coefficient = -44.72; P = 0.005), but increased from 60 to 180 minutes (coefficient = 27.03; P = 0.005). However, long-term studies found no significant effects of whole grains on fasting concentrations of GLP-1 or GIP.

CONCLUSION

Whole grain intake did not affect postprandial levels of GLP-1 but enhanced postprandial levels of GIP from 60 to 180 minutes. Further high-quality trials are required to assess the long-term effects of whole grain intake on serum levels of incretins.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021256695.

The importance of molecular weight in determining the minimum dose of oat β-glucan required to reduce the glycaemic response in healthy subjects without diabetes: a systematic review and meta-regression analysis

To determine the minimum amount of oat β-glucan (OBG) required to reduce glycaemic responses (MinDose), we conducted a systematic review and meta-regression analysis of acute, crossover, single-meal feeding trials that examined the effects of adding OBG or oat bran to a carbohydrate-containing test-meal versus a control test-meal containing an equivalent amount of available-carbohydrate (avCHO) from the same or similar source. Medline, Embase, and Cochrane Library were searched up to 18 August 2021. The primary outcome was glucose incremental-area-under-the-curve (iAUC). Secondary outcomes included insulin iAUC, and glucose and insulin incremental peak-rise (iPeak). Two independent reviewers extracted data. Results were expressed as ratio-of-means (RoM) with 95% confidence intervals (CIs). Linear associations were assessed by random effects meta-regression. MinDose was defined as the dose at which the upper 95% CI of the regression line cut the line of no effect (i.e., RoM = 1). Fifty-nine comparisons (n = 340) were included; 57 in healthy subjects without diabetes and two in subjects with diabetes; 24 high-MW (>1000 kg/mol), 22 medium-MW (300-1,000 kg/mol), and 13 low-MW (<300 kg/mol). In healthy subjects without diabetes the associations between OBG dose and glucose iAUC and iPeak were linear (non-linear p value >0.05). MinDoses for glucose iAUC for high-MW, medium-MW and low-MW OBG, respectively, were estimated to be 0.2 g, 2.2 g and 3.2 g per 30 g avCHO; MinDoses for glucose iPeak were less than those for iAUC. Insufficient data were available to assess MinDose for insulin, however, there was no evidence of a disproportionate increase in insulin. More high-quality trials are needed to establish MinDose in individuals with diabetes.

Modulation of Postprandial Plasma Concentrations of Digestive Hormones and Gut Microbiota by Foods Containing Oat ß-Glucans in Healthy Volunteers

Cereal β-glucans are beneficial health ingredients that reduce cholesterolemia and postprandial glycaemia. However, their impact on digestive hormones and gut microbiota is not yet fully established. Two randomized, double-blind, controlled studies were conducted. In the first study, 14 subjects ingested a breakfast with or without β-glucan from oats (5.2 g). Compared to the control, β-glucan increased orocecal transit time (p = 0.028) and decreased mean appetite score (p = 0.014) and postprandial plasma ghrelin (p = 0.030), C-peptide (p = 0.001), insulin (p = 0.06), and glucose (p = 0.0006). β-glucan increased plasma GIP (p = 0.035) and PP (p = 0.018) without affecting leptin, GLP-1, PYY, glucagon, amylin, or 7α-hydroxy-4-cholesten-3-one, a biomarker of bile acid synthesis. In the second study, 32 subjects were distributed into 2 groups to ingest daily foods with (3 g/day) or without β-glucan for 3 weeks; stools were collected before/after treatment. No changes in fecal microbiota composition/diversity (deep sequencing) were detected with β-glucans. These results indicate that acute intake of 5 g β-glucan slows transit time and decreases hunger sensation and postprandial glycaemia without affecting bile-acid synthesis, these changes being associated with decreased plasma insulin, C-peptide, and ghrelin, and increased plasma GIP and PP. However, regular daily intake of 3 g β-glucan is not sufficient to have an effect on fecal microbiota composition.

The Effects of Soluble Dietary Fibers on Glycemic Response: An Overview and Futures Perspectives

The properties of each food, composition, and structure affect the digestion and absorption of nutrients. Dietary fiber (DF), especially viscous DF, can contribute to a reduction in the glycemic response resulting from the consumption of carbohydrate-rich foods. Target and control of postprandial glycemic values are critical for diabetes prevention and management. Some mechanisms have been described for soluble DF action, from the increase in chyme viscosity to the production of short-chain fatty acids resulting from fermentation, which stimulates gastrointestinal motility and the release of GLP-1 and PYY hormones. The postprandial glycemic response due to inulin and resistant starch ingestion is well established. However, other soluble dietary fibers (SDF) can also contribute to glycemic control, such as gums, β-glucan, psyllium, arabinoxylan, soluble corn fiber, resistant maltodextrin, glucomannan, and edible fungi, which can be added alone or together in different products, such as bread, beverages, soups, biscuits, and others. However, there are technological challenges to be overcome, despite the benefits provided by the SDF, as it is necessary to consider the palatability and maintenance of their proprieties during production processes. Studies that evaluate the effect of full meals with enriched SDF on postprandial glycemic responses should be encouraged, as this would contribute to the recommendation of viable dietary options and sustainable health goals.

The role of cereal soluble fiber in the beneficial modulation of glycometabolic gastrointestinal hormones

According to cohort studies, cereal fiber, and whole-grain products might decrease risk for type 2 diabetes (T2DM), inflammatory processes, cancer, and cardiovascular diseases. These associations, mainly affect insoluble, but not soluble cereal fiber. In intervention studies, soluble fiber elicit anti-hyperglycemic and anti-inflammatory short-term effects, partially explained by fermentation to short-chain fatty acids, which acutely counteract insulin resistance and inflammation. ß-glucans lower cholesterol levels and possibly reduce liver fat. Long-term benefits are not yet shown, maybe caused by T2DM heterogeneity, as insulin resistance and fatty liver disease - the glycometabolic points of action of soluble cereal fiber - are not present in every patient. Thus, only some patients might be susceptive to fiber. Also, incretin action in response to fiber could be a relevant factor for variable effects. Thus, this review aims to summarize the current knowledge from human studies on the impact of soluble cereal fiber on glycometabolic gastrointestinal hormones. Effects on GLP-1 appear to be highly contradictory, while these fibers might lower GIP and ghrelin, and increase PYY and CCK. Even though previous results of specific trials support a glycometabolic benefit of soluble fiber, larger acute, and long-term mechanistic studies are needed in order to corroborate the results.

The role of dietary fibers in regulating appetite, an overview of mechanisms and weight consequences

Dietary fibers prevent obesity through reduction of hunger and prolongation of satiety. A number of mechanical and endocrine signals from gastrointestinal tract are stimulated by fibers and their fermentation products, reach regions of brain involved in the regulation of appetite, and ultimately reduce food intake. Gastric distention, delayed gastric emptying, prevention of hypoglycemic, increased amounts of unabsorbed nutrients reaching to the ileum, and stimulation of enteroendocrine cells for secretion of cholecystokinin, glucagon-like peptide-1 (GLP-1), and peptide YY are among mechanisms of fibers in decreasing hunger and prolongation of satiety. Fermentation of fibers produces short-chain fatty acids that also stimulates enteroendocrine cells to secrete GLP-1 and PYY. Randomized controlled trials have shown reductions in energy intake and body weight along with increased satiation and reduced hunger following consumption of fibers. Prospective cohort studies have confirmed these results but the extent of weight loss in some studies has been small. Controversies exist between studies particularly for the effect of fibers on the gastrointestinal hormones, subsequent food intake, and the resultant weight loss. More studies are needed before a clear conclusion can be drawn especially for the effect of fibers on appetite-related hormones and weight loss.

Effects of whole-grain barley and oat β-glucans on postprandial glycemia and appetite: a randomized controlled crossover trial

This study aimed to determine the postprandial effects of barley bread (BB) and oat bread (OB), grain sources of β-glucans, on glycaemia and appetite by comparison with white bread (WB) and whole-wheat bread (WWB). This randomized controlled crossover trial included 20 healthy individuals (10 males and 10 females) who consumed WB, WWB, BB, and OB with a standard breakfast followed by an ad libitum lunch. Postprandial glucose and appetite responses were quantified as the incremental area under the curve (iAUC). Although the iAUC for glycaemic response was lower by 23.7%, 29.9%, and 27.9% after the consumption of BB, OB, and WWB compared with WB (p = 0.023), no differences were observed between BB, OB, and WWB (p > 0.05). BB had a lower iAUC for appetite sensation by 21.5%, 23.9%, and 55.7% compared with WB, WWB, and OB (p = 0.005). OB had no effect on appetite and was also less palatable than BB. Subsequent food intakes were similar after the consumption of all test breads (p > 0.05). The encouragement of healthier bread formulations that can beneficially modulate postprandial glycemia and appetite may contribute to the promotion of public health. This trial was registered at ClinicalTrials.gov as NCT04749498.

The Effect of Rye-Based Foods on Postprandial Plasma Insulin Concentration: The Rye Factor

Consumption of whole grain has been associated with lower incidence of type-2 diabetes, cardiovascular disease and their risk factors including improved glycemic control. In comparison with other whole grain products, rye bread has been shown to induce lower insulin response in the postprandial phase, without affecting the glucose response. This phenomenon has been referred to as the “rye factor” and is being explored in this review where we summarize the findings from meal and extended meal studies including rye-based foods. Overall, results from intervention studies showed that rye-based foods vs. (wheat) control foods had positive effect on both insulin and glucose responses in the postprandial phase, rather than on insulin alone. Mechanistic studies have shown that the rye factor phenomenon might be due to slowing of the glucose uptake in the intestine. However, this has also been shown for wheat-based bread and is likely an effect of structural properties of the investigated foods rather than the rye per se. More carefully controlled studies where standardized structural properties of different cereals are linked to the postprandial response are needed to further elucidate the underlying mechanisms and determinants for the effect of specific cereals and product traits on postprandial glycemic control.

Elucidating the role of the gut microbiota in the physiological effects of dietary fiber

BACKGROUND

Dietary fiber is an integral part of a healthy diet, but questions remain about the mechanisms that underlie effects and the causal contributions of the gut microbiota. Here, we performed a 6-week exploratory trial in adults with excess weight (BMI: 25-35 kg/m2) to compare the effects of a high-dose (females: 25 g/day; males: 35 g/day) supplement of fermentable corn bran arabinoxylan (AX; n = 15) with that of microbiota-non-accessible microcrystalline cellulose (MCC; n = 16). Obesity-related surrogate endpoints and biomarkers of host-microbiome interactions implicated in the pathophysiology of obesity (trimethylamine N-oxide, gut hormones, cytokines, and measures of intestinal barrier integrity) were assessed. We then determined whether clinical outcomes could be predicted by fecal microbiota features or mechanistic biomarkers.

RESULTS

AX enhanced satiety after a meal and decreased homeostatic model assessment of insulin resistance (HOMA-IR), while MCC reduced tumor necrosis factor-α and fecal calprotectin. Machine learning models determined that effects on satiety could be predicted by fecal bacterial taxa that utilized AX, as identified by bioorthogonal non-canonical amino acid tagging. Reductions in HOMA-IR and calprotectin were associated with shifts in fecal bile acids, but correlations were negative, suggesting that the benefits of fiber may not be mediated by their effects on bile acid pools. Biomarkers of host-microbiome interactions often linked to bacterial metabolites derived from fiber fermentation (short-chain fatty acids) were not affected by AX supplementation when compared to non-accessible MCC.

CONCLUSION

This study demonstrates the efficacy of purified dietary fibers when used as supplements and suggests that satietogenic effects of AX may be linked to bacterial taxa that ferment the fiber or utilize breakdown products. Other effects are likely microbiome independent. The findings provide a basis for fiber-type specific therapeutic applications and their personalization.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT02322112 , registered on July 3, 2015. Video Abstract.

Whole grain intake, compared to refined grain, improves postprandial glycemia and insulinemia: a systematic review and meta-analysis of randomized controlled trials

Whole grain (WG) intake has been associated with reduced risk of type 2 diabetes (T2D) and may protect against T2D by lowering postprandial glycemia and insulinemia and improving insulin sensitivity. The objective of this systematic review and meta-analysis was to evaluate the effect of WG intake, compared to refined grain (RG) intake, on postprandial glycemia and insulinemia and markers of glycemic control and insulin resistance in randomized controlled trials (RCTs) in adults. A search of PubMed and Scopus yielded 80 relevant RCTs. Compared to RG, WG intake significantly reduced postprandial glycemia (SMD: -0.30; 95% CI: -0.43, -0.18; P < 0.001), insulinemia (SMD: -0.23; 95% CI: -0.35, -0.10; P < 0.001) and glycated hemoglobin (HbA1c) (SMD: -0.21; 95% CI: -0.37, -0.06; P = 0.007). There was no effect of WG on fasting glucose, fasting insulin, or homeostatic model assessment of insulin resistance (HOMA-IR). These results suggest WG foods improve short-term glycemia and insulinemia, which may improve HbA1c, a marker of long-term glycemic control. This may partially explain the inverse association between WG intake and risk of T2D, but further investigations are needed to understand if short-term reductions in glycemia translate to longer term benefits in reducing the risk of T2D.Systematic Review Registration: PROSPERO Registration CRD42020180069.

Pleurotus eryngii improves postprandial glycaemia, hunger and fullness perception, and enhances ghrelin suppression in people with metabolically unhealthy obesity

The aim of this study was to examine potential postprandial benefits of Pleurotus eryngii in nineteen volunteers with metabolically unhealthy obesity. An acute, randomized, crossover-designed trial comparing a meal with Pleurotus eryngii and a control meal was performed. The two meals matched in macronutrient and caloric content. Participants consumed both meals in random order after an overnight fast. Blood samples were drawn before and 30, 60, 90, 120, 150 and 180 min after meal consumption (in total 266 samples) to determine glucose, insulin, ghrelin, peptide YY, glucagon-like peptide-1 and glicentin. Visual analog scales measuring the subjective perception of hunger and fullness were completed at the same time points. The test meal resulted in lower glucose incremental area under the curve (iAUC). Additionally, the iAUC of the ghrelin response over time was substantially lower after the test meal (p = 0.033). Lower desire to eat and higher fullness was reflected by significantly lower hunger iAUC (p = 0.046) and higher fullness iAUC (p = 0.042) after the test meal. No differences in insulin, PYY, GLP-1 and glicentin were observed. Pleurotus eryngii can ameliorate postprandial glycaemia, appetite and regulate ghrelin levels at the postprandial state. This effect is attributed to the bioactive polysaccharides that inhibit the activity of enzymes catalysing carbohydrate hydrolysis, cause a delayed gastric emptying and glucose absorption.

The effect of oat β-glucan on postprandial blood glucose and insulin responses: a systematic review and meta-analysis

To determine the effect of oat β‑glucan (OBG) on acute glucose and insulin responses and identify significant effect modifiers we searched the MEDLINE, EMBASE, and Cochrane databases through October 27, 2020 for acute, crossover, controlled feeding trials investigating the effect of adding OBG (concentrate or oat-bran) to carbohydrate-containing test-meals compared to comparable or different carbohydrate-matched control-meals in humans regardless of health status. The primary outcome was glucose incremental area-under-the-curve (iAUC). Secondary outcomes were insulin iAUC, and glucose and insulin incremental peak-rise (iPeak). Two reviewers extracted the data and assessed risk-of-bias and certainty-of-evidence (GRADE). Data were pooled using generic inverse-variance with random-effects model and expressed as ratio-of-means with [95% CIs]. We included 103 trial comparisons (N = 538). OBG reduced glucose iAUC and iPeak by 23% (0.77 [0.74, 0.81]) and 28% (0.72 [0.64, 0.76]) and insulin by 22% (0.78 [0.72, 0.85]) and 24% (0.76 [0.65, 0.88]), respectively. Dose, molecular-weight, and comparator were significant effect modifiers of glucose iAUC and iPeak. Significant linear dose-response relationships were observed for all outcomes. OBG molecular-weight >300 kg/mol significantly reduced glucose iAUC and iPeak, whereas molecular-weight <300 kg/mol did not. Reductions in glucose iAUC (27 vs 20%, p = 0.03) and iPeak (39 vs 25%, p < 0.01) were significantly larger with different vs comparable control-meals. Outcomes were similar in participants with and without diabetes. All outcomes had high certainty-of-evidence. In conclusion, current evidence indicates that adding OBG to carbohydrate-containing meals reduces glycaemic and insulinaemic responses. However, the magnitude of glucose reduction depends on OBG dose, molecular-weight, and the comparator.

Effects of Whole Grain Intake, Compared with Refined Grain, on Appetite and Energy Intake: A Systematic Review and Meta-Analysis

Results from observational studies indicate that whole grain (WG) intake is inversely associated with BMI and risk of weight gain. WG intake may influence energy balance and body composition through effects on appetite and energy intake. To evaluate the impact of WG food consumption on appetite and energy intake, a systematic review and meta-analysis was performed of results from randomized controlled trials (RCTs) assessing WG food consumption, appetite, and energy intake in adults. A search of PubMed, Scopus, and Food Science and Technology Abstracts yielded 36 RCTs measuring subjective appetite ratings after consuming WG foods compared with refined grain (RG) controls. Thirty-two of these studies reported AUCs for subjective appetite (hunger, fullness, satiety, desire to eat, or prospective consumption) and/or energy intake and were included in the meta-analysis. Pooled estimates from meta-analyses are expressed as standardized mean differences (SMDs). Compared with RG foods, intake of WG foods resulted in significant differences in AUCs for subjective hunger (SMD: -0.34; 95% CI: -0.46, -0.22; P < 0.001), fullness (SMD: 0.49; 95% CI: 0.31, 0.66; P < 0.001), satiety (SMD: 0.33; 95% CI: 0.18, 0.47; P < 0.001), and desire to eat (SMD: -0.33; 95% CI: -0.46, -0.20; P < 0.001). There were small, nonsignificant reductions in prospective consumption ratings (P = 0.08) and energy intake (P = 0.07) with WG intake compared with RG. These results support the view that consumption of WG foods, compared with RG foods, significantly impacts subjective appetite, and might partly explain the inverse associations between WG food intake and risk of overweight, obesity, and weight gain over time. PROSPERO registration: CRD42020148217.

The Relationship between In Vitro and In Vivo Starch Digestion Kinetics of Breads Varying in Dietary Fibre

The relationship between in vitro and in vivo starch digestion kinetics was studied in portal vein catheterised pigs fed breads varying in dietary fibre (DF) content and composition. The breads were a low DF white wheat bread, two high DF whole grain rye breads without and with whole kernels and two experimental breads with added arabinoxylan or oat β-glucan concentrates, respectively. In vitro, samples were collected at 0, 5, 10, 15, 30, 60, 120 and 180 min and the cumulative hydrolysis curve for starch was modelled, whereas the in vivo cumulative absorption models for starch were based on samples taken every 15 min up to 60 min and then every 30 min up to 240 min. The starch hydrolysis rate in vitro (0.07 to 0.16%/min) was far higher than the rate of glucose appearance in vivo (0.017 to 0.023% absorbed starch/min). However, the ranking of the breads was the same in vitro and in vivo and there was a strong relationship between the kinetic parameters.

Plant-Based Food By-Products: Prospects for Valorisation in Functional Bread Development

The industrial and small-scale processing of plant-based food materials is associated with by-products that may have a negative impact on the environment but could add value to bread-based products. The bioactivity of plant-based food by-products, their impact on the properties of functional bread, and their bioavailability/bioaccessibility leading to potential health effects when consumed was reviewed. Plant-based food by-products which may be added to bread include rice bran, wheat bran, corn bran, grape pomace/seed extract, tomato seed/skin, and artichoke stems/leaves. These by-products contain high concentrations of bioactive compounds, including phenolics, bioactive peptides, and arabinoxylan. Pre-treatment procedures, including fermentation and thermal processing, impact the properties of plant-based by-products. In most cases, bread formulated with flour from plant-based by-products demonstrated increased fibre and bioactive compound contents. In terms of the sensory and nutritional acceptability of bread, formulations with an average of 5% flour from plant-based by-products produced bread with acceptable sensory properties. Bread enriched with plant-based by-products demonstrated enhanced bioavailability and bioaccessibility and favourable bioactive properties in human blood, although long-term studies are warranted. There is a need to investigate the bioactive properties of other underutilised plant-based by-products and their potential application in bread as a sustainable approach towards improving food and nutrition security.

Dietary fibre and protein do not synergistically influence insulin, metabolic or inflammatory biomarkers in young obese Göttingen minipigs

The effects of dietary fibre (DF) and protein on insulin response, lipidaemia and inflammatory biomarkers were studied in a model experiment with juvenile obese Göttingen minipigs. After 20 weeks feeding on a high-fat fructose-rich low-DF diet, forty-three 30-week-old minipigs (31·3 (sem 4·0) kg body weight) were allocated to low- or high-DF and -protein diets for 8 weeks in a 2 × 2 factorial design. High DF contents decreased (P = 0·006) while high protein increased (P < 0·001) the daily gain. High protein contents increased fasting plasma concentrations of glucose (P = 0·008), NEFA (P = 0·015), ghrelin (P = 0·008) and non-fasting LDL:HDL ratios (P = 0·015). High DF increased ghrelin (P = 0·036) and C-peptide levels (P = 0·011) in the non-fasting state. High protein increased the gene expression of fructose-bisphosphatase 1 in liver tissue (P = 0·043), whereas DF decreased fatty acid synthase expression in adipose tissue (P = 0·035). Interactions between DF and protein level were observed in the expression of leptin receptor in adipose tissue (P = 0·031) and of PPARγ in muscle (P = 0·018) and adipose tissue (P = 0·004). In conclusion, high DF intake reduced weight gain and had potential benefit on β-cell secretory function, but without effect on the lipid profile in this young obese model. High dietary protein by supplementing with whey protein did not improve insulin sensitivity or lipidaemia, and combining high DF with high protein did not alleviate the risk of metabolic abnormalities.

Enrichment of bread with beta-glucans or resistant starch induces similar glucose, insulin and appetite hormone responses in healthy adults

PURPOSE

β-Glucans (βG) and resistant starch (RS) are known for their effects on the improvement of glucose tolerance and enhancement of insulin sensitivity. Enrichment of bread with βG or RS was performed to examine potential postprandial benefits regarding gastrointestinal hormone responses.

METHODS

Ten healthy normoglycaemic adults participated in the study and were provided with either a glucose solution (reference food, GS) or bread enriched with β-glucans (βGB) (3.6 g/30 g available CHO) or bread enriched with resistant starch (RSB) (15% of total starch), with 1-week intervals in amounts that yielded 50 g of available carbohydrates. Venous blood samples were collected before consumption and at 15, 30, 45, 60, 90, 120 and 180 min postprandially. Glucose, insulin, ghrelin, glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) responses as well as glycaemic index (GI) and subjective appetite ratings were evaluated.

RESULTS

Ingestion of βGB and RSB elicited lower incremental area under the curve (iAUC) for glycaemic response compared to GS (P < 0.05). Both breads demonstrated a low GI (βGB: 48, RSB: 40). There were no significant differences in insulin response, ghrelin, GLP-1 or PYY between the two breads. A significantly lower desire to eat and higher fullness were detected 15 min after βGB and RSB consumption and until 180 min (P < 0.05 compared to GS).

CONCLUSION

Enrichment of bread with either βG or RS produced a low GI product but the two breads were not significantly different in relation to insulin, ghrelin, GLP-1 and PYY responses. The development of bread products which cause improved metabolic effects is of great importance for the promotion of public health.

Whole grain food diet slightly reduces cardiovascular risks in obese/overweight adults: a systematic review and meta-analysis

BACKGROUND

The effects of whole grain diet on cardiovascular risks in obese and overweight adults is not well established. Our goal was to conduct a systematic review and meta-analysis on the effect of whole grain diet on cardiovascular risks in obese/overweight adults.

METHODS

PubMed, Embase and Cochrane were systematically scanned for randomized controlled trials (RCTs), and studies were selected based on certain inclusion and exclusion criteria. The primary outcome was the effectiveness of whole grain food consumption in reducing body weight. The secondary outcomes were the effect of whole grain food consumption on cardiovascular disease (CVD) risk factors including plasma low-density lipoprotein cholesterol (LDL-C), insulin resistance index, blood pressure, body mass index (BMI), C-reactive protein (CRP), and waist circumference in obese/overweight adults.

RESULTS

Our results showed that whole grain consumption was associated with lower body weight (mean difference (MD) = - 0.5, 95% confidence intervals (CI) [- 0.74, 0.25], I2 = 35%, P < 0.0001) and lower CRP (MD = -0.36, 95% CI [- 0.54, - 0.18], I2 = 69%, P < 0.0001), compared with the control group. However, there were no significant differences in LDL-C (MD = -0.08, 95% CI [- 0.16, 0.00], I2 = 27%, P = 0.05), waist circumference (MD = -0.12, 95% CI [- 0.92, 0.68], I2 = 44%, P = 0.76), systolic blood pressure (MD = -0.11, 95% CI [- 1.55, 1.33], I2 = 3%, P = 0.88), diastolic blood pressure (MD = -0.44, 95% CI [- 1.44, 0.57], I2 = 15%, P = 0.39), and fasting glucose (MD = -0.05, 95% CI [- 0.12, 0.01], I2 = 31%, P = 0.11) between the two groups.

CONCLUSION

This study suggests that whole grain food consumption can slightly reduce body weight and CRP in obese/overweight population.

Incretin Hormones: The Link between Glycemic Index and Cardiometabolic Diseases

This review aimed to describe the potential mechanisms by which incretin hormones could mediate the relationship between glycemic index and cardiometabolic diseases. A body of evidence from many studies suggests that low glycemic index (GI) diets reduces the risk for type 2 diabetes and coronary heart disease. In fact, despite the extensive literature on this topic, the mechanisms underlying unfavorable effects of high GI foods on health remain not well defined. The postprandial and hormonal milieu could play a key role in the relationship between GI and cardiovascular risk. Incretin hormones, glucagon-like peptide1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are important regulators of postprandial homeostasis by amplifying insulin secretory responses. Response of GIP and GLP-1 to GI have been studied more in depth, also by several studies on isomaltulose, which have been taken as an ideal model to investigate the kinetics of incretin secretion in response to foods’ GI. In addition, extrapancreatic effects of these incretin hormones were also recently observed. Emerging from this have been exciting effects on several targets, such as body weight regulation, lipid metabolism, white adipose tissue, cardiovascular system, kidney, and liver, which may importantly affect the health status.

Cereal B-Glucans: The Impact of Processing and How It Affects Physiological Responses

Cereal β-glucans are dietary fibres primarily found in oats and barley, and have several positive effects on health, including lowering the postprandial glucose response and the improvement of blood cholesterol levels. Cereal β-glucans have a specific combination of β-(1→4) and β-(1→3) linkages into linear long-chain polysaccharides of high molecular weight. Due to their particular structure, cereal β-glucans generate viscosity within the intestinal tract, which is thought to be the main mechanism of action responsible for their positive health effects. However, cereal grains are rarely consumed raw; at least one cooking step is generally required before they can be safely eaten. Cooking and processing methods more generally will modify the physicochemical characteristics of β-glucans, such as molecular weight, extractability and the resulting viscosity. Therefore, the health impact of β-glucans will depend not only on the dose administered, but also on the ways they are processed or converted into food products. This review aims at summarizing the different parameters that can affect β-glucans efficacy to improve glucose and lipid metabolism in humans.

A Whole-Grain Diet Increases Glucose-Stimulated Insulin Secretion Independent of Gut Hormones in Adults at Risk for Type 2 Diabetes

INTRODUCTION

The effect of whole-grain (WG) versus refined-grain (RG) diets on glucose-stimulated insulin secretion (GSIS) and β-cell function is unclear.

METHODS

In a double-blind crossover randomized controlled trial, 13 prediabetic adults (37.2 ± 1.8 y, BMI: 33.6 ± 1.4 kg m^-2 , 2 h glucose: 146.9 ± 11.6 mg dL^-1 ) are provided isocaloric-matched WG and RG diets for 8-weeks each, with an 8-10 week washout between diets. Glucose, insulin, and C-peptide are studied over 240 min following a 75 g OGTT. Incretins (GLP-1 and GIP), PYY, and total ghrelin are assessed at 0, 30, and 60 min. Mixed-meal diets for carbohydrate (54%), fat (28%), and protein (18%) contain either WG (50 g/1000 kcal) or equivalent RG.

RESULTS

Both diets induce fat loss (≈2 kg). While neither diet impacts early phase GSIS, the WG diet increases total GSIS (iAUC of C-peptide_0-240 /Glc_0-240 , p = 0.02) and β-cell function (disposition index; GSIS × insulin sensitivity, p = 0.02). GIP and PYY are unaltered by either diet, but GLP-1 is higher at 30 min following RG versus WG (p = 0.04). Ghrelin levels are higher at 60 min of the OGTT following both interventions (p = 0.01).

CONCLUSION

A WG-rich diet increases β-cell function independent of gut hormones in adults with prediabetes.

Nutritional interest of dietary fiber and prebiotics in obesity: Lessons from the MyNewGut consortium

The aim of EU project MyNewGut is to contribute to future public health-related recommendations supported by new insight in gut microbiome and nutrition-host relationship. In this Opinion Paper, we first revisit the concept of dietary fiber, taking into account their interaction with the gut microbiota. This paper also summarizes the main effects of dietary fibers with prebiotic properties in intervention studies in humans, with a particular emphasis on the effects of arabinoxylans and arabinoxylo-oligosaccharides on metabolic alterations associated with obesity. Based on the existing state of the art and future development, we elaborate the steps required to propose dietary guidelines related to dietary fibers, taking into account their interaction with the gut microbiota.

Wholegrain Intake and Risk of Type 2 Diabetes: Evidence from Epidemiological and Intervention Studies

Type 2 diabetes mellitus (T2DM) is one of the most common metabolic diseases and represents a leading cause of morbidity and mortality because of its related complications. The alarming rise in T2DM prevalence worldwide poses enormous challenges in relation to its social, economic, and a clinical burden requiring appropriate preventive strategies. Currently, lifestyle modifications—including approaches to promote a moderate body weight reduction and to increase regular physical exercise—are the first crucial intervention for T2DM prevention. In the light of the difficulty in reducing body weight and in long-term maintenance of weight loss, quality changes in dietary patterns—in terms of macro and micronutrient composition—can also strongly affect the development of T2DM. This may provide a more practical and suitable preventative approach than simply implementing caloric restriction. Along this line, there is increasing evidence that wholegrain consumption in substitution of refined grains is associated with a reduction of the incidence of several non-communicable chronic diseases. The aim of the present review is to summarize the current evidence from observational and randomized controlled clinical trials on the benefits of wholegrain on T2DM prevention and treatment. Plausible mechanisms by which wholegrain could act on glucose homeostasis and T2DM prevention are also evaluated. Altogether, the totality of the available evidence supports present dietary recommendations promoting wholegrain foods for the prevention and treatment of T2DM.

Impact of Rye Kernel-Based Evening Meal on Microbiota Composition of Young Healthy Lean Volunteers With an Emphasis on Their Hormonal and Appetite Regulations, and Blood Levels of Brain-Derived Neurotrophic Factor

Rye kernel bread (RKB) evening meals improve glucose tolerance, enhance appetite regulation and increase satiety in healthy volunteers. These beneficial effects on metabolic responses have been shown to be associated with increased gut fermentation. The present study aimed to elucidate if RKB evening meals may cause rapid alterations in microbiota composition that might be linked to metabolic-, immune-, and appetite- parameters. Gut-brain axis interaction was also studied by relating microbiota composition to amount of brain-derived neurotrophic factor (BDNF) in blood plasma. Nineteen healthy volunteers, ten women and nine men aged 22–29 years, BMI < 25 (NCT02093481) participated in the study performed in a crossover design. Each person was assigned to either white wheat bread (WWB) or RKB intake as a single evening meal or three consecutive evenings. Stool and blood samples as well as subjective appetite ratings were obtained the subsequent morning after each test occasion, resulting in four independent collections per participant (n = 76). DNA was extracted from the fecal samples and V4 hypervariable region of the bacterial 16S rRNA genes was sequenced using next generation sequencing technology. Higher abundance of Prevotella and Faecalibacterium with simultaneous reduction of Bacteroides spp. were observed after RKB meals compared to WWB. The associations between metabolic test variables and microbiota composition showed a positive correlation between Bacteroides and adiponectin levels, whereas only Prevotella genus was found to have positive association with plasma levels of BDNF. These novel findings in gut-brain interactions might be of importance, since decreased levels of BDNF, that plays an essential role in brain function, contribute to the pathogenesis of several major neurodisorders, including Alzheimer's. Thus, daily consumption of Faecalibacterium- and/or Prevotella-favoring meals should be investigated further for their potential to prevent neurodegenerative processes in the brain.

Subjective satiety and plasma PYY concentration after wholemeal pasta

Dietary fiber and whole grain foods may contribute to the regulation of appetite; however, evidence has produced inconclusive findings. The objective was to evaluate the effects of an experimental wholemeal pasta on appetite ratings, plasma concentrations of gastrointestinal hormones involved in appetite control, and postprandial glucose/insulin responses in healthy adults. Fourteen healthy adults (7M/7F), mean age 30±2 yrs (mean±SEM), participated in a randomized, controlled, crossover trial. Participants consumed on two different days, at one week interval, 117g of wholemeal pasta or 100g of refined wheat pasta (control pasta), similar in energy and macronutrient composition except for fiber amount, which was higher in wholemeal pasta (11 vs 3 g). Appetite ratings, glucose/insulin/lipid and gastrointestinal hormone responses were measured at fasting and for 4-h after the ingestion of the pasta tests, after which self-reported energy intake for 8-h was evaluated. After the wholemeal pasta, the desire to eat and the sensation of hunger were lower (-16%, p=0.04 and -23%, p=0.004, respectively) and satiety was higher (+13%; p=0.08) compared with the control pasta; no effect on self-reported energy intake at subsequent meal was observed. After wholemeal pasta, glucose, triglyceride increased and GLP-1 responses were not different compared to control pasta but insulin response at 30 min (p<0.05) and ghrelin at 60 min (p=0.03) were lower and PYY levels higher (AUC=+44%, p=0.001). The appetite rating changes correlated with PYY plasma levels (p<0.03). In conclusion, consumption of whole grain instead of refined wheat pasta contributed to appetite control but did not seem to influence acute energy balance. Appetite ratings were associated with modifications in PYY hormone concentrations.

Beta-glucans and cancer: The influence of inflammation and gut peptide

Dietary β-glucans are soluble fibers with potentially health-promoting effects. Gut peptides are important signals in the regulation of energy and glucose homeostasis. This article reviews the effects of different enriched β-glucan food consumption on immune responses, inflammation, gut hormone and cancer. Gut hormones are influenced by enriched β-glucan food consumption and levels of such peptide as YY, ghrelin, glucagon-like peptide 1 and 2 in humans influence serum glucose concentration as well as innate and adaptive immunity. Cancer cell development is also regulated by obesity and glucose dishomeostasy that are influenced by β-glucan food consumption that in turn regulated gut hormones.

Addition of Rye Bran and Pea Fiber to Pork Meatballs Enhances Subjective Satiety in Healthy Men, but Does Not Change Glycemic or Hormonal Responses: A Randomized Crossover Meal Test Study

Background: The development of high-protein, fiber-rich foods targeting appetite control could be an efficient tool in obesity prevention.Objectives: We investigated whether ad libitum energy intake (EI), appetite, and metabolic markers in a meal context were affected by 1) fiber addition (rye bran and pea fiber) to pork meatballs, 2) the food matrix of the fiber (fiber meatballs compared with fiber bread), or 3) the protein source (animal compared with vegetable protein patties).Methods: In a crossover design, 40 healthy men [mean ± SD: body mass index (BMI; in kg/m2), 22.2 ± 1.9; age, 23.3 ± 2.9 y] consumed 4 test meals: a low-fiber meal consisting of pork meatballs plus wheat bread (LF meal); pork meatballs plus fiber bread; fiber meatballs plus wheat bread, and vegetable patties with a natural fiber content plus wheat bread (∼3000 kJ; protein ∼18% of energy, carbohydrate ∼50% of energy, fat ∼30% of energy; 13 g fiber in the fiber meals). Ad libitum EI after 4 h was the primary endpoint. Moreover, appetite sensations and postprandial responses of glucose, insulin, glucagon-like peptide-1, peptide YY 3-36, and plasma amino acids were measured.Results: Ad libitum EI did not differ significantly between the meals. Satiety and fullness increased 11% and 13%, respectively, and hunger and prospective intake decreased 17% and 15%, respectively, after the meal of fiber meatballs plus wheat bread compared with the LF meal (P < 0.01). Hormonal and metabolic responses did not differ between the meals. In general, plasma amino acid concentrations were higher after the fiber-rich meals than after the LF meal.Conclusions: Meals based on meatballs and bread with differences in the fiber content, food matrix of fiber, and protein source had similar effects on ad libitum EI in healthy men. However, fiber addition to pork meatballs favorably affected appetite sensations but without changes in hormonal and metabolic responses. Moreover, animal- and vegetable-protein-based, fiber-matched meals had similar effects on appetite regulation. This trial was registered at clinicaltrials.gov as NCT02521805.

Dietary steamed wheat bran increases postprandial fat oxidation in association with a reduced blood glucose-dependent insulinotropic polypeptide response in mice

Obesity is a global epidemic associated with a higher risk of cardiovascular disease and metabolic disorders, such as type 2 diabetes. Previous studies demonstrated that chronic feeding of steamed wheat bran (WB) decreases obesity. To clarify the underlying mechanism and the responsible component for the anti-obesity effects of steamed WB, we investigated the effects of dietary steamed WB and arabinoxylan on postprandial energy metabolism and blood variables. Overnight-fasted male C57BL/6J mice were fed an isocaloric diet with or without steamed WB (30%). Energy metabolism was evaluated using an indirect calorimeter, and plasma glucose, insulin, and glucose-dependent insulinotropic polypeptide (GIP) levels were measured for 120 min after feeding. We similarly investigated the effect of arabinoxylan, a major component of steamed WB. Mice fed the WB diet had higher postprandial fat oxidation and a lower blood GIP response compared with mice fed the control diet. Mice fed the arabinoxylan diet exhibited a dose-dependent postprandial blood GIP response; increasing the arabinoxylan content in the diet led to a lower postprandial blood GIP response. The arabinoxylan-fed mice also had higher fat oxidation and energy expenditure compared with the control mice. In conclusion, the findings of the present study revealed that dietary steamed WB increases fat oxidation in mice. Increased fat oxidation may have a significant role in the anti-obesity effects of steamed WB. The postprandial effects of steamed WB are due to arabinoxylan, a major component of WB. The reduction of the postprandial blood GIP response may be responsible for the increase in postprandial fat utilization after feeding on a diet containing steamed WB and arabinoxylan.

Wholegrain rye, but not wholegrain wheat, lowers body weight and fat mass compared with refined wheat: a 6-week randomized study

BACKGROUND

Observational studies suggest inverse associations between wholegrain intake and body weight gain. Only few controlled intervention studies have supported this association and few compare effects of different grain varieties.

OBJECTIVE

To investigate how wholegrain wheat (WGW) and rye compared with refined wheat (RW) affect body weight and composition and appetite sensation.

DESIGN

Seventy overweight/obese adults participated in this 6-week randomized parallel study, in which they replaced their habitual cereal foods with RW, WGW or wholegrain rye (WGR). Further, a 4 h postprandial test meal challenge was completed with meals corresponding to diet allocation in the beginning and after the intervention. Body weight and composition, fasted blood samples, compliance and 4-day dietary intake were obtained before and after the intervention period. Appetite and breath hydrogen excretion was assessed during the postprandial test meal challenge.

RESULTS

Diet allocation affected body weight significantly (P=0.013) and tended also to affect fat mass (P=0.065). Both body weight and fat mass decreased more in the WGR group (-1.06±1.60 and -0.75±1.29 kg, respectively) compared with the RW group (+0.15±1.28 and -0.04±0.82 kg, respectively; P<0.01 and P<0.05, respectively). Further, the decrease in fat mass in the WGR group tended to exceed that in the WGW group (P=0.07). Overall, no effect of diet on appetite sensation was observed; however, energy intake from study products was ~200 kcal lower in the WGR group when compared with that in the RW group (P<0.05), although total energy intake did not differ between groups.

CONCLUSIONS

Our results support a role for WGR foods in body weight regulation, when provided ad libitum. The effect may be mediated by satiation reflected in a reduction in energy intake, mainly from the wholegrain products without compensation in other parts of the diets, despite no difference in appetite.

Targeted metabolomics reveals differences in the extended postprandial plasma metabolome of healthy subjects after intake of whole-grain rye porridges versus refined wheat bread

SCOPE

We previously found that whole-grain (WG) rye porridges suppressed appetite and improved glucose metabolism. This study aimed to investigate potential plasma metabolites that may be related to differences in those appetite and glucose responses.

METHODS AND RESULTS

Twenty-one health subjects consumed six isocaloric breakfasts in a randomized cross-over study. Plain WG rye porridges (40 and 55 g), rye porridge enriched with different inulin: gluten proportions (9:3 g; 6:6 g; 3:9 g), and a 55 g refined wheat bread (control) were served as part of complete breakfast, followed by a standardized lunch. NMR metabolomics assessed 36 plasma metabolites and short chain fatty acids were measured by GC-MS from baseline up to 8 h. Pre-lunch plasma essential amino acids reflected protein composition and post-lunch plasma short chain fatty acids varied with fiber content in breakfasts. No correlations were observed between measured metabolites and glucose, insulin, or appetite responses.

CONCLUSIONS

Differences in protein and fiber contents in breakfasts altered postprandial plasma amino acids and short chain fatty acids, respectively, but were unrelated to appetite and glucose responses. Further studies are warrant to identify the underlying mechanisms for the beneficial effects on appetite and second meal glucose responses after rye-based foods.

Rye polyphenols and the metabolism of n-3 fatty acids in rats: a dose dependent fatty fish-like effect

As long-chain fatty acids (LCFA) of the n-3 series are critically important for human health, fish consumption has considerably increased in recent decades, resulting in overfishing to respond to the worldwide demand, to an extent that is not sustainable for consumers’ health, fisheries economy, and marine ecology. In a recent study, it has been shown that whole rye (WR) consumption improves blood and liver n-3 LCFA levels and gut microbiota composition in rats compared to refined rye. The present work demonstrates that specific colonic polyphenol metabolites may dose dependently stimulate the synthesis of n-3 LCFA, possibly through their microbial and hepatic metabolites in rats. The intake of plant n-3 alpha-linolenic acid and WR results in a sort of fatty fish-like effect, demonstrating that the n-3 LCFA levels in blood and tissues could be increased without eating marine foods, and therefore without promoting unsustainable overfishing, and without damaging marine ecology.

Effects of whole-grain rye porridge with added inulin and wheat gluten on appetite, gut fermentation and postprandial glucose metabolism: a randomised, cross-over, breakfast study

Whole-grain rye foods reduce appetite, insulin and sometimes glucose responses. Increased gut fermentation and plant protein may mediate the effect. The aims of the present study were to investigate whether the appetite-suppressing effects of whole-grain rye porridge could be enhanced by replacing part of the rye with fermented dietary fibre and plant protein, and to explore the role of gut fermentation on appetite and metabolic responses over 8 h. We conducted a randomised, cross-over study using two rye porridges (40 and 55 g), three 40-g rye porridges with addition of inulin:gluten (9:3; 6:6; 3:9 g) and a refined wheat bread control (55 g), served as part of complete breakfasts. A standardised lunch and an ad libitum dinner were served 4 and 8 h later, respectively. Appetite, breath hydrogen and methane, glucose, insulin and glucagon-like peptide-1 (GLP-1) responses were measured over 8 h. Twenty-one healthy men and women, aged 23-60 years, with BMI of 21-33 kg/m2 participated in this study. Before lunch, the 55-g rye porridges lowered hunger by 20 % and desire to eat by 22 % and increased fullness by 29 % compared with wheat bread (P<0·05). Breath hydrogen increased proportionally to dietary fibre content (P<0·05). Plasma glucose after lunch was 6 % lower after the 55-g rye porridges compared with wheat bread (P<0·05) and correlated to breath hydrogen (P<0·001). No differences were observed in ad libitum food intake, insulin or GLP-1. We conclude that no further increase in satiety was observed when replacing part of the rye with inulin and gluten compared with plain rye porridges.

Effects of Arabinoxylan and Resistant Starch on Intestinal Microbiota and Short-Chain Fatty Acids in Subjects with Metabolic Syndrome: A Randomised Crossover Study

Recently, the intestinal microbiota has been emphasised as an important contributor to the development of metabolic syndrome. Dietary fibre may exert beneficial effects through modulation of the intestinal microbiota and metabolic end products. We investigated the effects of a diet enriched with two different dietary fibres, arabinoxylan and resistant starch type 2, on the gut microbiome and faecal short-chain fatty acids. Nineteen adults with metabolic syndrome completed this randomised crossover study with two 4-week interventions of a diet enriched with arabinoxylan and resistant starch and a low-fibre Western-style diet. Faecal samples were collected before and at the end of the interventions for fermentative end-product analysis and 16S ribosomal RNA bacterial gene amplification for identification of bacterial taxa. Faecal carbohydrate residues were used to verify compliance. The diet enriched with arabinoxylan and resistant starch resulted in significant reductions in the total species diversity of the faecal-associated intestinal microbiota but also increased the heterogeneity of bacterial communities both between and within subjects. The proportion of Bifidobacterium was increased by arabinoxylan and resistant starch consumption (P<0.001), whereas the proportions of certain bacterial genera associated with dysbiotic intestinal communities were reduced. Furthermore, the total short-chain fatty acids (P<0.01), acetate (P<0.01) and butyrate concentrations (P<0.01) were higher by the end of the diet enriched with arabinoxylan and resistant starch compared with those resulting from the Western-style diet. The concentrations of isobutyrate (P = 0.05) and isovalerate (P = 0.03) decreased in response to the arabinoxylan and resistant starch enriched diet, indicating reduced protein fermentation. In conclusion, arabinoxylan and resistant starch intake changes the microbiome and short-chain fatty acid compositions, with potential beneficial effects on colonic health and metabolic syndrome.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01618526.

Feed-forward neural network model for hunger and satiety related VAS score prediction

BACKGROUND

An artificial neural network approach was chosen to model the outcome of the complex signaling pathways in the gastro-intestinal tract and other peripheral organs that eventually produce the satiety feeling in the brain upon feeding.

METHODS

A multilayer feed-forward neural network was trained with sets of experimental data relating concentration-time courses of plasma satiety hormones to Visual Analog Scales (VAS) scores. The network successfully predicted VAS responses from sets of satiety hormone data obtained in experiments using different food compositions.

RESULTS

The correlation coefficients for the predicted VAS responses for test sets having i) a full set of three satiety hormones, ii) a set of only two satiety hormones, and iii) a set of only one satiety hormone were 0.96, 0.96, and 0.89, respectively. The predicted VAS responses discriminated the satiety effects of high satiating food types from less satiating food types both in orally fed and ileal infused forms.

CONCLUSIONS

From this application of artificial neural networks, one may conclude that neural network models are very suitable to describe situations where behavior is complex and incompletely understood. However, training data sets that fit the experimental conditions need to be available.