Unabsorbable carbohydrates and diabetes: Decreased post-prandial hyperglycaemia

Mechanistic Understanding of the Effects of Pectin on In Vivo Starch Digestion: A Review

Obesity and type II diabetes are closely related to the rapid digestion of starch. Starch is the major food-energy source for most humans, and thus knowledge about the regulation of starch digestion can contribute to prevention and improved treatment of carbohydrate metabolic disorders such as diabetes. Pectins are plant polysaccharides with complex molecular structures and ubiquitous presence in food, and have diverse effects on starch digestion. Pectins can favorably regulate in vivo starch digestion and blood glucose level responses, and these effects are attributed to several reasons: increasing the viscosity of digesta, inhibiting amylase activity, and regulating some in vivo physiological responses. Pectins can influence starch digestion via multiple mechanisms simultaneously, in ways that are highly structure-dependent. Utilizing the multi-functionalities of pectin could provide more ways to design low glycemic-response food and while avoiding the unpalatable high viscosity in food by which is commonly caused by many other dietary fibers.

The solution properties of galactomannan after simulated digestion of guar fortified bread predict the extent of postprandial insulin reduction in healthy adult overweight subjects

Coil overlap occurs when random coil polysaccharides such as cereal beta-glucan or galactomannan in solution are abundant enough and large enough to entangle with one another to form networks. It was recently shown that this concept applied to in vitro digested cereal-based foods could predict the efficacy of the food to reduce postprandial glycaemia. In the current study we further investigate the role of coil overlap for prediction of glycaemic and insulinaemic responses using four guar fortified breads (10-15% wheat flour replacement level) with galactomannans of different weight-average molecular weight (M_w). The breads, including a wheat flour control, were tested in a randomised crossover study in 12 overweight adults. Addition of guar reduced postprandial serum insulin, but not glucose responses. The extent of postprandial insulin reduction correlated with the solution properties of galactomannan after in vitro digestion. A significantly greater reduction in insulin response was observed for two of the breads where the galactomannan M_w and concentration in solution after in vitro digestion was above coil overlap, in contrast to two other breads, which resulted in digests containing galactomannan below coil overlap and a significantly lower reduction of postprandial insulin. Further in vitro digestion experiments focusing on amylolysis of starch with kinetic modelling showed a greater proportion of slowly digested starch in breads with galactomannan above coil overlap than below. A combination of the molecular weight of dietary fibre in a food and its soluble concentration are key parameters explaining its physiological efficiency in the upper gastrointestinal tract.

Blood glucose response after oral lactulose intake in type 2 diabetic individuals

BACKGROUND

Lactulose is approved for the symptomatic treatment of constipation, a gastrointestinal (GI) complication common in individuals with diabetes. Lactulose products contain carbohydrate impurities (e.g., lactose, fructose, galactose), which occur during the lactulose manufacturing process. These impurities may affect the blood glucose levels of individuals with type 2 diabetes mellitus (T2DM) using lactulose for the treatment of mild constipation. A previous study in healthy subjects revealed no increase in blood glucose levels after oral lactulose intake. However, it is still unclear whether the intake of lactulose increases blood glucose levels in individuals with diabetes.

AIM

To evaluate the blood glucose profile after oral lactulose intake in mildly constipated, non-insulin-dependent subjects with T2DM in an outpatient setting.

METHODS

This prospective, double-blind, randomized, controlled, single-center trial was conducted at the Clinical Research Center at the Medical University of Graz, Austria, in 24 adult Caucasian mildly constipated, non-insulin-dependent subjects with T2DM. Eligible subjects were randomized and assigned to one of six treatment sequences, each consisting of four treatments stratified by sex using an incomplete block design. Subjects received a single dose of 20 g or 30 g lactulose (crystal and liquid formulation), water as negative control or 30 g glucose as positive control. Capillary blood glucose concentrations were measured over a period of 180 min post dose. The primary endpoint was the baseline-corrected area under the curve of blood glucose concentrations over the complete assessment period [AUC_{baseline_c (0-180 min)}]. Quantitative comparisons were performed for both lactulose doses and formulations vs water for the equal lactulose dose vs glucose, as well as for liquid lactulose vs crystal lactulose. Safety parameters included GI tolerability, which was assessed at 180 min and 24 h post dose, and adverse events occurring up to 24 h post dose.

RESULTS

In 24 randomized and analyzed subjects blood glucose concentration-time curves after intake of 20 g and 30 g lactulose were almost identical to those after water intake for both lactulose formulations despite the different amounts of carbohydrate impurities (≤ 3.0% for crystals and approx. 30% for liquid). The primary endpoint [AUC_{baseline_c (0-180 min)}] was not significantly different between lactulose and water regardless of lactulose dose and formulation. Also with regard to all secondary endpoints lactulose formulations showed comparable results to water with one exception concerning maximum glucose level. A minor increase in maximum blood glucose was observed after the 30 g dose, liquid lactulose, in comparison to water with a mean treatment difference of 0.63 mmol/L (95% confidence intervals: 0.19, 1.07). Intake of 30 g glucose significantly increased all blood glucose endpoints vs 30 g liquid and crystal lactulose, respectively (all P < 0.0001). No differences in blood glucose response were observed between the different lactulose formulations. As expected, lactulose increased the number of bowel movements and was generally well tolerated. Subjects experienced only mild to moderate GI symptoms due to the laxative action of lactulose.

CONCLUSION

Blood glucose AUC_{baseline_c (0-180 min)} levels in mildly constipated, non-insulin dependent subjects with T2DM are not affected by the carbohydrate impurities contained in 20 g and 30 g crystal or liquid lactulose formulations.

Factors Affecting Gut Microbiome in Daily Diet

There is a growing recognition that a good diet can help people maintain mental and physical health, while a bad one will cause the disorder of body function, and even lead to several diseases. A lot of attentions have been devoted to analyze every possible health-related factor in the daily diet, including food ingredients, additives, and cooking process. With the support of high-throughput sequencing technology, there is accumulating evidence gradually clarifying that most of these factors are mainly through the interactions with gut microbiome to trigger downstream effects. The gut microbiome may be able to act as a very sensitive mirror in response to human daily diet. A complex network of interactions among diet, gut microbiome, and health has been gradually depicted, but it is rarely discussed from a more comprehensive perspective. To this end, this review summarized the latest updates in diet-gut microbiome interactions, analyzed most identified factors involved in this process, showed the possibility of maintaining health or alleviating diseases by diet intervention, aiming to help people choose a suitable recipe more accurately.

Targeting Carbohydrates and Polyphenols for a Healthy Microbiome and Healthy Weight

Purpose of Review

In this review, we focus on microbiota modulation using non-digestible carbohydrate and polyphenols (i.e., prebiotics) that have the potential to modulate body weight.

Recent Findings

Prebiotics derived from plants have gained the interest of public and scientific communities as they may prevent diseases and help maintain health.

Summary

Maintaining a healthy body weight is key to reducing the risk of developing chronic metabolic complications. However, the prevalence of obesity has increased to pandemic proportions and is now ranked globally in the top five risk factors for death. While diet and behavioral modification programs aiming to reduce weight gain and promote weight loss are effective in the short term, they remain insufficient over the long haul as compliance is often low and weight regain is very common. As a result, novel dietary strategies targeting the gut microbiota have been successful in decreasing obesity and metabolic disorders via different molecular mechanisms.

Title: Differentiating the effects of whey protein and guar gum preloads on postprandial glycemia in type 2 diabetes

BACKGROUND AND AIMS

Whey protein and guar gum have both been reported to reduce postprandial glycemia in health and type 2 diabetes, associated with stimulation of glucagon-like peptide-1 (GLP-1) and/or slowing of gastric emptying. Our aim was to evaluate, in type 2 diabetes, the acute effects of low dose "preloads" of whey and guar, given alone or in combination before a meal, on postprandial glycemia, insulin, GLP-1, and gastric emptying.

METHODS

21 patients with type 2 diabetes, managed by diet or metformin alone, were each studied on 4 days. They received a preload "shake" 15min before a mashed potato meal (368.5 kcal) labeled with ¹³C-octanoic-acid. The preloads comprised either (i) 17 g whey (W), (ii) 5 g guar (G), (iii) 17 g whey + 5 g guar (WG) each sweetened with 60 mg sucralose, and (iv) 60 mg sucralose alone (control; C), all dissolved in 150 mL water. Venous blood was sampled frequently for measurements of glucose, insulin, and GLP-1 concentrations. Gastric half-emptying time (T50) was calculated from breath ¹³CO₂ excretion over 240 min.

RESULTS

Postprandial blood glucose concentrations were lower with W and WG compared to C (each P < 0.0001, treatment × time interaction), and lower after G than C only at 30min. Insulin, GLP-1, and glucagon concentrations were higher after W than WG, G, or C (P < 0.05, treatment × time interaction), without differences between the latter three. Gastric emptying was slower with W (T50: 179.6 ± 6.1 min, P < 0.05) and WG (T50: 197.6 ± 9.7 min, P < 0.0001) when compared to C (T50: 162.9 ± 6.2 min), but did not differ between G (T50: 171.3 ± 7.0) and C (P > 0.99).

CONCLUSION

Both whey and whey/guar preloads reduced postprandial glycemia, associated with slowing of gastric emptying. Low dose guar was less effective as a preload for glucose-lowering and did not slow gastric emptying.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

Australian and New Zealand Clinical Trials Registry, Trial ID ACTRN12615001272583, http://www.anzctr.org.au.

The Effects of a Whey Protein and Guar Gum-Containing Preload on Gastric Emptying, Glycaemia, Small Intestinal Absorption and Blood Pressure in Healthy Older Subjects

A whey protein/guar gum preload reduces postprandial glycaemia in type 2 diabetes through slowing gastric emptying. However, gastric emptying has previously been assessed using a stable isotope breath test technique, which cannot discriminate between slowing of gastric emptying and small intestinal absorption. This preload also may be useful in the management of postprandial hypotension. We evaluated the effects of a whey protein/guar preload on gastric emptying, glucose absorption, glycaemic/insulinaemic and blood pressure (BP) responses to an oral glucose load. Eighteen healthy older participants underwent measurements of gastric emptying (scintigraphy), plasma glucose and insulin, glucose absorption, superior mesenteric artery (SMA) flow, BP and heart rate (HR) after ingesting a 50 g glucose drink, with or without the preload. The preload reduced plasma glucose (p = 0.02) and serum 3-O-methylglucose (3-OMG) (p = 0.003), and increased plasma insulin (p = 0.03). There was no difference in gastric emptying or BP between the two days. The reduction in plasma glucose on the preload day was related to the reduction in glucose absorption (r = 0.71, p = 0.002). In conclusion, the glucose-lowering effect of the preload may relate to delayed small intestinal glucose absorption and insulin stimulation, rather than slowing of gastric emptying.

The Gut Microbiome Influences Host Endocrine Functions

The gut microbiome is considered an organ contributing to the regulation of host metabolism. Since the relationship between the gut microbiome and specific diseases was elucidated, numerous studies have deciphered molecular mechanisms explaining how gut bacteria interact with host cells and eventually shape metabolism. Both metagenomic and metabolomic analyses have contributed to the discovery of bacterial-derived metabolites acting on host cells. In this review, we examine the molecular mechanisms by which bacterial metabolites act as paracrine or endocrine factors, thereby regulating host metabolism. We highlight the impact of specific short-chain fatty acids on the secretion of gut peptides (i.e., glucagon-like peptide-1, peptide YY) and other metabolites produced from different amino acids and regulating inflammation, glucose metabolism, or energy homeostasis. We also discuss the role of gut microbes on the regulation of bioactive lipids that belong to the endocannabinoid system and specific neurotransmitters (e.g., γ-aminobutyric acid, serotonin, nitric oxide). Finally, we review the role of specific bacterial components (i.e., ClpB, Amuc_1100) also acting as endocrine factors and eventually controlling host metabolism. In conclusion, this review summarizes the recent state of the art, aiming at providing evidence that the gut microbiome influences host endocrine functions via several bacteria-derived metabolites.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.

Association between dietary fibre:carbohydrate intake ratio and insulin resistance in Japanese adults without type 2 diabetes

An easily understandable index that measures the quality of carbohydrate may aid people in adopting dietary habits that improve their glucose tolerance. We aimed to evaluate the relationship between a ratio of dietary fibre to carbohydrate intakes (fibre:carbohydrate ratio (F:C-R)) and glucose tolerance cross-sectionally and longitudinally. Subjects were 190 Japanese men and women without type 2 diabetes (mean age 55·4 years) who participated in a 5-month diet and exercise programme. We compared baseline anthropometric, dietary and metabolic profiles between those with higher F:C-R and those with lower ratios. Multivariable regression analyses were performed to examine the associations between the F:C-R and homoeostasis model of assessment for insulin resistance (HOMA-IR) and HbA1c at baseline and between changes in the F:C-R and changes in HOMA-IR and HbA1c over the 5-month period. At baseline, the higher F:C-R group had significantly lower body weight, lean body mass, fasting insulin level and HOMA-IR as compared with the lower F:C-R group. The two groups had similar intakes of carbohydrate and fat, whereas protein intake was greater in the high F:C-R group. Baseline F:C-R was not significantly associated with HOMA-IR or HbA1c at the beginning of the study in multivariable models. Increases in the ratio during the 5-month programme was associated with reductions in HbA1c (P<0·001). These findings highlight the potential utility of the F:C-R in strategies aimed at type 2 diabetes prevention.

The impact of diet-based glycaemic response and glucose regulation on cognition: evidence across the lifespan

The brain has a high metabolic rate and its metabolism is almost entirely restricted to oxidative utilisation of glucose. These factors emphasise the extreme dependence of neural tissue on a stable and adequate supply of glucose. Whereas initially it was thought that only glucose deprivation (i.e. under hypoglycaemic conditions) can affect brain function, it has become apparent that low-level fluctuations in central availability can affect neural and consequently, cognitive performance. In the present paper the impact of diet-based glycaemic response and glucose regulation on cognitive processes across the lifespan will be reviewed. The data suggest that although an acute rise in blood glucose levels has some short-term improvements of cognitive function, a more stable blood glucose profile, which avoids greater peaks and troughs in circulating glucose is associated with better cognitive function and a lower risk of cognitive impairments in the longer term. Therefore, a habitual diet that secures optimal glucose delivery to the brain in the fed and fasting states should be most advantageous for the maintenance of cognitive function. Although the evidence to date is promising, it is insufficient to allow firm and evidence-based nutritional recommendations. The rise in obesity, diabetes and metabolic syndrome in recent years highlights the need for targeted dietary and lifestyle strategies to promote healthy lifestyle and brain function across the lifespan and for future generations. Consequently, there is an urgent need for hypothesis-driven, randomised controlled trials that evaluate the role of different glycaemic manipulations on cognition.

Randomized clinical study: Partially hydrolyzed guar gum (PHGG) versus placebo in the treatment of patients with irritable bowel syndrome

Background

The treatment of Irritable bowel syndrome (IBS) is still challenging. Partially hydrolyzed guar gum (PHGG) is a known prebiotic fiber. To assess the effects of PHGG on clinical symptoms of IBS patients in a prospective randomized double blind placebo-controlled study.

Methods

Suitable IBS patients were recruited into an 18-week-long study (2 weeks of run-in, 12 weeks of treatment and 4 weeks of follow-up). They were blindly randomized to receive 6 gr of PHGG or placebo. Treatment efficacy was evaluated by the Francis Severity IBS score, the IBS quality-of-life scores and scored parameters of weekly journal of symptoms. Deltas of changes between the final and baseline scores were compared between two groups.

Results

Of 121 patients who underwent randomization, 108 patients (49 in the PHGG group and 59 in the placebo group) had all the data needed for intention-to-treat analysis. A 12-week administration of PHGG led to a significant improvement of journal bloating score in the PHGG group versus placebo (−4.1±13.4 versus −1.2±11.9, P=0.03), as well as in bloating+gasses score (−4.3±10.4 versus −1.12±10.5, P = 0.035). The effect lasted for at least 4 weeks after the last PHGG administration. PHGG had no effect on other journal reported IBS symptoms or on Severity and Quality of life scores. There were no significant side effects associated with PHGG ingestion. The rate of dropouts was significantly higher among patients in the placebo group compared with the PHGG group (49.15% versus 22.45%, respectively, P = 0.01).

Conclusions

The results of this study support the administration of 6 g/day PHGG for IBS patients with bloating.

Trial registration

NCT01779765

Food structure is critical for optimal health

Much nutrition policy is nutrient-based, supported by nutrient science, food nutrient composition tables and dietary nutrient recommendations, but not by reference to food structure.

Second-meal effects of pulses on blood glucose and subjective appetite following a standardized meal 2 h later

This study investigated whether pulses (chickpeas, yellow peas, navy beans, lentils) have an effect on blood glucose (BG) and appetite following a fixed-size meal 2 h later. Over the following 2 h, all pulses lowered BG area under the curve (AUC) and lentils reduced appetite AUC compared with white bread (p < 0.05). Following the meal, BG was lower after lentils and chickpeas at 150 and 165 min, and AUC was lower after lentils compared with white bread (p < 0.05).

Effects of consumption of main and side dishes with white rice on postprandial glucose, insulin, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 responses in healthy Japanese men

The co-ingestion of protein, fat and fibre with carbohydrate reportedly affects postprandial glucose, insulin and incretin (glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)) responses. However, the effects of combination dishes with carbohydrate-rich foods at typically eaten amounts remain unclear. The objective of the present study was to evaluate the effects of consuming recommended amounts of side dishes with boiled white rice in the same meal on postprandial plasma glucose, insulin and incretin hormone responses. A total of nine healthy male volunteers consumed four different meals in a random order on separate days. The test meals were as follows: S, white rice; SM, addition of protein-rich main dishes to the S meal; SMF, addition of a fat-rich food item to the SM meal; SMFV, addition of vegetables to the SMF meal. Plasma glucose, GIP and GLP-1 and serum insulin concentrations were determined during a 3 h period after consumption of these meals. Postprandial glucose responses were lower after SMFV meal consumption than after consumption of the other meals. The incremental AUC for GIP (0–180 min) were largest after consumption of the SMF and SMFV meals, followed by that after SM meal consumption, and was smallest after S meal consumption (P< 0·05). Furthermore, we found GIP concentrations to be dose dependently increased by the fat content of meals of ordinary size, despite the amount of additional fat being small. In conclusion, the combination of recommended amounts of main and vegetable side dishes with boiled white rice is beneficial for lowering postprandial glucose concentrations, with an increased incretin response, when compared with white rice alone.

Transglucosidase improves the gut microbiota profile of type 2 diabetes mellitus patients: a randomized double-blind, placebo-controlled study

Background

Recently, the relationship between gut microbiota and obesity has been highlighted. The present randomized, double-blind, placebo-controlled study aimed to evaluate the efficacy of transglucosidase (TGD) in modulating blood glucose levels and body weight gain in patients with type 2 diabetes mellitus (T2DM) and to clarify the underlying mechanism by analyzing the gut microbiota of T2DM patients.

Methods

This study included 60 patients who received placebo or TGD orally (300 or 900 mg/day) for 12 weeks, and blood and fecal samples were collected before and after 12 weeks. Comparisons of fecal bacterial communities were performed before and after the TGD treatment and were performed between T2DM patients and 10 healthy individuals, using the terminal-restriction fragment length polymorphism analysis.

Results

The Clostridium cluster IV and subcluster XIVa components were significantly decreased, whereas the Lactobacillales and Bifidobacterium populations significantly increased in the T2DM patients compared with the healthy individuals. By dendrogram analysis, most of the healthy individuals (6/10) and T2DM patients (45/60) were classified into cluster I, indicating no significant difference in fecal bacterial communities between the healthy individuals and the T2DM patients. In the placebo and TGD groups, the bacterial communities were generally similar before and after the treatment. However, after 12 weeks of TGD therapy, the Bacteroidetes-to-Firmicutes ratio in the TGD groups significantly increased and was significantly higher compared with that in the placebo group, indicating that TGD improved the growth of the fecal bacterial communities in the T2DM patients.

Conclusions

Therefore, TGD treatment decreased blood glucose levels and prevented body weight gain in the T2DM patients by inducing the production of oligosaccharides in the alimentary tract and modulating gut microbiota composition.

Trial registration

UMIN-CTR UMIN000010318

Food-based ingredients to modulate blood glucose

Maintenance of normal blood glucose levels is important for avoiding chronic diseases such as type 2 diabetes, cardiovascular problems, and obesity. Type 2 diabetes is one of the major health problems affecting the world population and this condition can be exacerbated by poor diet, low physical activity, and genetic abnormalities. Food plays an important role in the management of blood glucose and associated complications in diabetes. This is attributed to the ability of food-based ingredients to modulate blood glucose without causing any adverse health consequences. This chapter focuses on four important food groups such as cereals, legumes, fruits, and spices that have active ingredients such as soluble dietary fiber, polyphenols, and antinutrients with the ability to reduce glycemic and insulin response in humans. Other food ingredients such as simple sugars, sugar alcohols, and some proteins are also discussed in moderation.

A novel strategy in production of oligosaccharides in digestive tract: prevention of postprandial hyperglycemia and hyperinsulinemia

The aim of this study was to evaluate the effects of oral administration of transglucosidase (TG) on postprandial glucose concentrations in healthy subjects. A randomized placebo-controlled three-way crossover trial was separated by a washout period of more than 3 days. Twenty-one normal healthy volunteers, aged 30-61 years old (17 males and 4 females) were selected for this study. The subjects' health was assessed as normal by prestudy screening. All subjects received 3 types of test meals (3 rice balls: protein, 14.4 g; fat, 2.1 g; and carbohydrate, 111 g: total energy, 522 kcal) with 200 ml water in which 0 mg, 150 mg, or 300 mg of TG was dissolved. Blood samples for estimating plasma glucose and insulin concentrations were collected before and every 30 min after the experiment. As compared to no TG treatment, TG administration tended to prevent a postprandial increase in plasma glucose (p = 0.069: 150 mg of TG vs control) but there were no significant difference among three groups. With regard to the 17 subjects who were suggested to have impaired glucose tolerance, TG significantly decreased the postprandial blood glucose (p<0.05: 150 mg and 300 mg of TG vs control) and marginally decreased insulin concentrations (p = 0.099: 300 mg of TG vs control). These results suggest that TG may be useful for preventing the progression of type 2 diabetes mellitus.

Mechanisms underlying the cholesterol-lowering properties of soluble dietary fibre polysaccharides

A number of studies have shown a positive relationship between diets rich in soluble dietary fibres (SDF) such as β-glucan, pectin, guar gum and psyllium, and reduced serum cholesterol and thus a decreased risk of cardiovascular disease (CVD). Three major biological mechanisms have been proposed to explain the cholesterol-reducing effects of SDF: prevention of bile salt (BS) re-absorption from the small intestine leading to an excess faecal BS excretion; reduced glycemic response leading to lower insulin stimulation of hepatic cholesterol synthesis; and physiological effects of fermentation products of SDF, mainly propionate. Evidence for the latter mechanism is inconclusive, whereas in vivo, ex vivo and in vitro experiments suggest that BS micelles "bind" to SDF preventing their re-absorption. Whereas, glycemic responses to SDF have been studied extensively, the nature of interactions between bile salt micelles and SDF that lead to incomplete BS re-absorption are poorly defined. Three potential physicochemical mechanisms are proposed together with suggestions for in vitro experiments to test them.

Slowly digestible starch: concept, mechanism, and proposed extended glycemic index

Starch is the major glycemic carbohydrate in foods, and its nutritional property is related to its rate and extent of digestion and absorption in the small intestine. A classification of starch into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on the in vitro Englyst test is used to specify the nutritional quality of starch. Both the RDS and RS fractions have been extensively studied while there are only limited studies on the intermediate starch fraction of SDS, particularly regarding its structural basis and slow digestion mechanism. The current understanding of SDS including its concept, measurement method, structural basis and mechanism, physiological consequences, and approaches to make SDS is reviewed. An in vivo method of extended glycemic index (EGI) is proposed to evaluate its metabolic effect and related health consequences.

Fiber facts: benefits and recommendations for individuals with type 2 diabetes

In randomized controlled trials, viscous soluble fibers have demonstrated acute and long-term metabolic improvements in type 2 diabetes, such as reductions in hemoglobin A1c, fasting and post-prandial glycemia, insulinemia, and cardiovascular risk factors. In addition, they may be helpful in weight control through promoting feelings of fullness. Increasing consumption of foods containing fiber or use of fiber supplements could play an important role in managing diabetes with positive outcomes on vascular complications and reduced cardio-vascular disease risk.

Structure of a novel highly branched alpha-glucan enzymatically produced from maltodextrin

The bacterial strain PP710, isolated from soil and identified as Paenibacillus species, produced a low-digestibility alpha-glucan containing a large amylase-resistant portion. This alpha-glucan was obtained in high yields from maltodextrin (dextrose equivalent 3) by using the condensed culture supernatant of the strain as the enzyme preparation. The water-soluble dietary fiber content of the low-digestibility alpha-glucan was 80.2%, and showed resistance to a rat intestinal enzyme preparation. The alpha-glucan was found to be a novel highly branched alpha-glucan by acid hydrolysis, NMR analysis, gel permeation chromatography, methylation analysis, and enzymatic digestion.

Effect of different kinds of fibre on postprandial blood glucose in insulin-dependent diabetics

Dietary fibre may retard glucose absorption in normal and diabetic subjects. It is, however, unclear which type of fibre would be most suitable for this purpose. We therefore studied whether pectin differs from fibre from barley (85%) and citrus (15%) (Dumovital) in its effect on postprandial blood glucose responses. Eight insulin-dependent diabetics fasted overnight and were then given a meal without their morning insulin. The basic meal, composed of 90 g white bread and 120 g jam (total carbohydrate 105 g), was given three times: alone, with 15 g pectin and with 15 g Dumovital fibre. Blood glucose was measured for three hours. The tests showed that pectin administration considerably inhibited the postprandial rise in blood glucose, while Dumovital showed no such effect. Barley/citrus fibre (a mixture of cellulose, hemicellulose, lignin and pectin) has not the same inhibiting effect on postprandial rise in blood glucose as pure pectin in insulin-dependent diabetics. Thus, the specific type of fibre must be considered when prescribing dietary fibre to diabetics.

Effect of different fibers on glucose and lipid levels in diabetic subjects

The diabetic diet has traditionally been low in carbohydrate content. However, recent studies have shown that the diet may be liberalized in this respect provided that complex carbohydrates are given. When given in amounts corresponding to 50 g starch beans, in particular, raise the blood glucose levels to only a small extent and less than various other foodstuffs tested. The reason for this is, at least in part, due to the effect of the constituent fibers. Guar is another fiber of bean origin which has been shown to lower the postprandial glucose levels. Data from long-term treatment of diabetic patients with guar are presented.

Dietary supplementation of fibre (Lunelax) as a mean to reduce postprandial glucose in diabetics

The postprandial glucose concentrations after a standardized breakfast of 12 type II diabetics were followed and the effect of supplementation of a fibre-containing bulk-purgative (Lunelax) to the meal was investigated. It was found that addition of Lunelax reduced the mean increment glucose concentration with about 9%. The patients reported that Lunelax was convenient to take.

Comparable postprandial glucose reductions with viscous fiber blend enriched biscuits in healthy subjects and patients with diabetes mellitus: acute randomized controlled clinical trial

AIM

To compare the blood glucose-lowering effect of a highly viscous fiber blend (VFB) added to a starchy snack on postprandial glycemia between healthy participants and participants with diabetes mellitus.

METHODS

Ten healthy participants (4 men and 6 women, aged 28+/-2.6 years, body mass index [BMI], 24.3+/-0.8 kg/m(2)) and 9 participants with diabetes mellitus type 2 (3 men and 6 women, aged 68+/-3.8 years, BMI 28.8+/-1.2 kg/m(2)) on four separate occasions took either 50 g available carbohydrates as control biscuits, biscuits with 10 g of highly viscous fiber blend, white bread with 12 g of margarine, or white bread alone. Postprandial blood glucose response, glycemic index (GI), and palatability were determined.

RESULTS

Mean (95% confidence interval) GI values of the viscous fiber blend biscuits were 26 (16-36) and 37 (27-47) GI units for healthy participants and participants with diabetes mellitus, respectively. These values were significantly lower than those of white bread, white bread with 12 g of margarine, and control biscuits (P<0.001, paired t test) both in healthy participants (GI 100, 108 [57-159], and 101 [44-158], respectively) and participants with diabetes mellitus (GI 100, 103 [79-127], and 94 [78-110], respectively). Viscous fiber blend significantly reduced the glycemic index by 74% (7.4 GI units/g of fiber) in healthy participants and by 63% (6.3 GI units/g of fiber) in participants with diabetes. The GI did not differ between control meals in both healthy participants and participants with diabetes. There were no significant differences in palatability among the types of meals, although participants with diabetes found the viscous fiber blend biscuits more palatable (P=0.002, t test).

CONCLUSION

Viscous fiber blend is a very potent and palatable soluble fiber addition to a starchy snack, which is able to reduce the glycemic response to a similar extent in both healthy participants and individuals with diabetes mellitus. Biscuits with low GI, and possibly other viscous fiber blend fortified starchy foods, may potentially be a useful replacement of high GI snack foods in the diet.

Do fibre containing enteral diets have advantages over existing low residue diets?

This study investigated the influence of fibre on the pattern of absorption of protein and carbohydrate following administration of polymeric enteral diet and also the effect of added fibre on frequency of bowel action, stool weight and gastrointestinal side effects during enteral nutrition. No difference was seen in frequency of bowel action, stool weight or gastrointestinal side effects in five patients fed with either a fibre free polymeric diet or with the same diet augmented with 24 g fibre/24 h. Addition of fibre did not significantly alter breath hydrogen excretion. In an oral tolerance test on six normal subjects, the post prandial rises in blood glucose and levels of 17 amino acids were similar on ingestion of a fibre containing or fibre free test meal.

Dietary fibre, nuts and cardiovascular diseases

Dietary fibre has a range of metabolic health benefits. Through a variety of mechanisms, dietary fibre, and the viscous variety in particular, slows down gastric emptying and intestinal transit, decreases the rate of intestinal carbohydrate absorption, and increases faecal bile acid excretion. Therefore, consumption of some types of soluble fibre can enhance satiety, which is associated with a lower BMI, and reduce blood cholesterol and the postprandial glucose response. Surprisingly, the consumption of insoluble fibre from whole grains, though metabolically inert, has been associated with a reduction in the risk of developing coronary heart disease and diabetes in epidemiological studies. The likely reason is that whole grains, like nuts, legumes and other edible seeds, contain many bioactive phytochemicals and various antioxidants. After cereals, nuts are the vegetable foods that are richest in fibre, which may partly explain their benefit on the lipid profile and cardiovascular health.

Role of partially hydrolyzed guar gum in the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is the world's most common gastrointestinal functional disorder and is associated with several social and economic costs. Health-related quality of life is often impaired in patients with IBS. The pathophysiologic mechanisms underlying IBS remain poorly defined. The therapeutic approach to patients with IBS is based on symptoms, and fibers may play an important role in treatment. Among the various types of fiber, water-soluble, non-gelling fibers seem to be a promising option for treatment of IBS. Partially hydrolyzed guar gum (PHGG) is a water-soluble, non-gelling fiber that has provided therapeutic benefits. In clinical trials, PHGG decreased symptoms in constipation-predominant and diarrhea-predominant forms of IBS and decreased abdominal pain. Further, an improvement in quality of life was observed in patients with IBS during and after treatment with PHGG. Moreover, PHGG seems to have prebiotic properties because it increases the colonic contents of short-chain fatty acids, Lactobacilli, and Bifidobacteria.

The effects of Goami No. 2 rice, a natural fiber-rich rice, on body weight and lipid metabolism

OBJECTIVE

Increased intake of dietary fiber reduces the risk of obesity and type 2 diabetes. We assessed the effects of a fiber-rich diet on body weight, adipokine concentrations, and the metabolism of glucose and lipids in non-obese and obese subjects in Korea, where rice is the main source of dietary carbohydrates.

RESEARCH METHODS AND PROCEDURES

Eleven healthy, non-obese and 10 obese subjects completed two 4-week phases of individual isoenergetic food intake. During the control diet phase, subjects consumed standard rice; during the modified diet phase, subjects consumed equal proportions of fiber-rich Goami No. 2 rice and standard rice. We used a randomized, controlled, crossover study design with a washout period of 6 weeks between the two phases.

RESULTS

After the modified diet phase, body weight was significantly lower in both the non-obese and obese subjects (non-obese, 57.0 +/- 2.9 vs. 56.1 +/- 2.8 kg, p = 0.001; obese, 67.7 +/- 2.1 vs. 65.7 +/- 2.0 kg, p < 0.001 for before vs. after). The BMI was significantly lower in obese subjects (26.9 +/- 0.5 vs. 26.0 +/- 0.6 kg/m2, p < 0.001). The modified diet was associated with lower serum triacylglycerol (p < 0.01), total cholesterol (p < 0.01), low-density lipoprotein cholesterol (p < 0.05), and C-peptide (p < 0.05) concentrations in the obese subjects.

DISCUSSION

These results indicate that fiber-rich Goami No. 2 rice has beneficial effects and may be therapeutically useful for obese subjects.

Effects of Flax Fiber on Laxation and Glycemic Response in Healthy Volunteers

We investigated whether a flax supplement taken orally or baked in a bakery product would effect the physiological responses characteristic of soluble and insoluble fiber, i.e., laxation and glycemic response, respectively. In Study 1, 26 healthy young adults consumed up to 15 g of fiber from a proprietary flax fiber supplement or as a psyllium supplement for 2 weeks once usual fecal weights were established. Changes in dietary fiber intake and acceptability of both products were evaluated. An increase in fecal weight was found with both fiber treatments. Supplemental fiber at intakes of 9.0 g/day (flax) and 10.4 g/day (psyllium) gave fecal bulking capacity of about 2.9 and 4.8 g of fecal weight/g of fiber, respectively. In Study 2, the effect of flax bread versus control white bread on glycemic response was studied. Eleven fasting subjects completed four test periods (duplicate trials of each bread) under standardized glycemic testing conditions. Paired t tests were used to analyze test compared with control peak blood glucose values (6.6 +/- 0.9 mmol/L compared with 6.9 +/- 0.7 mmol/L, P < .05, respectively) and area under the curve (AUC) (669 +/- 53 compared with 693 +/- 57, P = .015, respectively). Peak blood glucose values and AUC were improved by ingestion of flax fiber in healthy subjects. In conclusion, a flax fiber supplement provides the benefits of soluble and insoluble fiber.

Dietary fibre, glycaemic response, and diabetes

The much publicised global trend in rising levels of obesity and diabetes has refuelled interest in the dietary intake of the macronutrients (fat, protein, and carbohydrates) necessary to maintain the state of normalcy (good health) of an individual. Both scientific and public attention have focused on the dietary mediation of chronic health syndromes, either through use of dietary supplements, or a review of the whole diet situation. Dietary supplements have been used extensively both as pharmacological supplements, food ingredients, in processed foods to aid weight control, and the regulation of glucose control for diabetic patients. Particular interest has focused on the use of dietary fibres, especially soluble dietary fibres (such as guar gum, locust bean gum, and psyllium fibres), resistant starch, and slowly digestible carbohydrates. These have been shown to alter food structure, texture, and viscosity, and hence the rate of starch degradation during digestion. Research has also illustrated an association between the rate of carbohydrate degradation during digestion, and the regulation of postprandial blood sugar and insulin levels. The current paper explores the potential use of dietary fibres in the treatment of obesity and diabetes.

Treatment effects of partially hydrolyzed guar gum on symptoms and quality of life of patients with irritable bowel syndrome. A multicenter randomized open trial

The effects of partially hydrolyzed guar gum (PHGG) were compared in patients with irritable bowel syndrome, at 10 g/day (N = 40) and 5 g/day (N = 46) for 12 weeks. Gastrointestinal symptoms (GSRS), quality of life (SF-36), and psychological symptoms (HADS) were evaluated at baseline, during treatment (months 1 and 3), and at follow-up (month 6). In both groups symptoms and quality of life improved significantly after the first month of administration until follow-up compared to those at baseline. However, the improvement was significantly reduced at follow-up compared to the end of treatment. PHGG was effective for improving somatic (gastrointestinal symptoms) and psychological (quality of life and psychological distress) symptoms over the short term. Since the improvement tended to decrease after the end of the treatment period, further studies should evaluate the benefits of PHGG at a maintenance dosage.