Involvement of small intestinal motility in blood glucose response to dietary fibre in man

Gastrointestinal Effects and Tolerance of Nondigestible Carbohydrate Consumption

Nondigestible carbohydrates (NDCs) are food components, including nonstarch polysaccharides and resistant starches. Many NDCs are classified as dietary fibers by the US FDA. Because of their beneficial effects on human health and product development, NDCs are widely used in the food supply. Although there are dietary intake recommendations for total dietary fiber, there are no such recommendations for individual NDCs. NDCs are heterogeneous in their chemical composition and physicochemical properties-characteristics that contribute to their tolerable intake levels. Guidance on tolerable intake levels of different NDCs is needed because overconsumption can lead to undesirable gastrointestinal side effects, further widening the gap between actual and suggested fiber intake levels. In this review, we synthesize the literature on gastrointestinal effects of NDCs that the FDA accepts as dietary fibers (β-glucan, pectin, arabinoxylan, guar gum, alginate, psyllium husk, inulin, fructooligosaccharides and oligofructose, galactooligosaccharides, polydextrose, cellulose, soy fiber, resistant maltodextrin/dextrin) and present tolerable intake dose recommendations for their consumption. We summarized the findings from 103 clinical trials in adults without gastrointestinal disease who reported gastrointestinal effects, including tolerance (e.g., bloating, flatulence, borborygmi/rumbling) and function (e.g., transit time, stool frequency, stool consistency). These studies provided doses ranging from 0.75-160 g/d and lasted for durations ranging from a single-meal tolerance test to 28 wk. Tolerance was NDC specific; thus, recommendations ranged from 3.75 g/d for alginate to 25 g/d for soy fiber. Future studies should address gaps in the literature by testing a wider range of NDC doses and consumption forms (solid compared with liquid). Furthermore, future investigations should also adopt a standard protocol to examine tolerance and functional outcomes across studies consistently.

Psyllium husk intake and risk of type 2 diabetes: an evidence-based scientific and regulatory review of a qualified health claim conducted by the US Food and Drug Administration

The US Food and Drug Administration (FDA) received a petition from a company requesting that FDA issue an authorized health claim for the relationship between psyllium husk and a reduced risk of type 2 diabetes. After an initial assessment of the available scientific evidence, FDA determined that significant scientific agreement was lacking for this substance-disease relationship, whereupon the company agreed to have its petition reviewed as a qualified health claim. This article describes the process FDA used in conducting an evidence-based review of the science underpinning the proposed claim and addresses certain safety issues associated with psyllium husk that FDA considered in its review of the petition. Of the 6 studies from which scientific conclusions could be drawn, as identified through FDA's review, psyllium husk significantly improved plasma glucose levels and insulin sensitivity in only 1 study. Therefore, FDA's enforcement discretion letter for this qualified health claim stated: "Psyllium husk may reduce the risk of type 2 diabetes, although the FDA has concluded that there is very little scientific evidence for this claim."

High wholegrain barley β-glucan lowers food intake but does not alter small intestinal macronutrient digestibility in ileorectostomised rats

Using barley cultivars differing widely in β-glucan content, we aimed to determine their effects on small intestinal macronutrient digestion in 24 ileorectostomised rats. The rats were fed 1 of 4 experimental diets, each containing a different barley variety, for 11 d. The diets had a content of 0, 2.1, 2.6 and 4.3 g of β-glucan/100 g. Feed intake and faecal excretion of fat, protein, starch, and non-starch polysaccharides were determined in the final 5 d of the study and apparent macronutrient digestibility calculated. Higher dietary levels of β-glucan (2.6% and 4.3%) lowered feed intake (by 15 and 19%, respectively) but final body weight was only lowered by the 4.3% β-glucan diet relative to rats fed the 0% β-glucan diet (all ps < 0.05). Protein, lipid and starch digestibility was unrelated to the dietary β-glucan content. Higher dietary levels of barley β-glucan lower feed intake of ileorectostomised rats, which is independent of intestinal fermentation and unrelated to macronutrient digestibility.

Gastrointestinal actions of glucagon-like peptide-1-based therapies: glycaemic control beyond the pancreas

The gastrointestinal hormone glucagon-like peptide-1 (GLP-1) lowers postprandial glucose concentrations by regulating pancreatic islet-cell function, with stimulation of glucose-dependent insulin and suppression of glucagon secretion. In addition to endocrine pancreatic effects, mounting evidence suggests that several gastrointestinal actions of GLP-1 are at least as important for glucose-lowering. GLP-1 reduces gastric emptying rate and small bowel motility, thereby delaying glucose absorption and decreasing postprandial glucose excursions. Furthermore, it has been suggested that GLP-1 directly stimulates hepatic glucose uptake, and suppresses hepatic glucose production, thereby adding to reduction of fasting and postprandial glucose levels. GLP-1 receptor agonists, which mimic the effects of GLP-1, have been developed for the treatment of type 2 diabetes. Based on their pharmacokinetic profile, GLP-1 receptor agonists can be broadly categorized as short- or long-acting, with each having unique islet-cell and gastrointestinal effects that lower glucose levels. Short-acting agonists predominantly lower postprandial glucose excursions, by inhibiting gastric emptying and intestinal glucose uptake, with little effect on insulin secretion. By contrast, long-acting agonists mainly reduce fasting glucose levels, predominantly by increased insulin and reduced glucagon secretion, with potential additional direct inhibitory effects on hepatic glucose production. Understanding these pharmacokinetic and pharmacodynamic differences may allow personalized antihyperglycaemic therapy in type 2 diabetes. In addition, it may provide the rationale to explore treatment in patients with no or little residual β-cell function.

Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis of data in euglycemic subjects, patients at risk of type 2 diabetes mellitus, and patients being treated for type 2 diabetes mellitus

BACKGROUND

A number of health benefits are associated with intake of soluble, viscous, gel-forming fibers, including reduced serum cholesterol and the attenuation of postprandial glucose excursions.

OBJECTIVE

We assess the effects of psyllium, which is a soluble, gel-forming, nonfermented fiber supplement, on glycemic control in patients who were being treated for type 2 diabetes mellitus (T2DM) and in patients who were at risk of developing T2DM.

DESIGN

A comprehensive search was performed of available published literature (Scopus scientific database) and clinical records stored by Procter & Gamble with the use of key search terms to identify clinical studies that assessed the glycemic effects of psyllium in nondiabetic, pre-T2DM, and T2DM patients.

RESULTS

We identified 35 randomized, controlled, clinical studies that spanned 3 decades and 3 continents. These data were assessed in 8 meta-analyses. In patients with T2DM, multiweek studies (psyllium dosed before meals) showed significant improvement in both the fasting blood glucose (FBG) concentration (-37.0 mg/dL; P < 0.001) and glycated hemoglobin (HbA1c) [-0.97% (-10.6 mmol/mol); P = 0.048]. Glycemic effects were proportional to baseline FBG; no significant glucose lowering was observed in euglycemic subjects, a modest improvement was observed in subjects with pre-T2DM, and the greatest improvement was observed in subjects who were being treated for T2DM.

CONCLUSIONS

These data indicate that psyllium would be an effective addition to a lifestyle-intervention program. The degree of psyllium's glycemic benefit was commensurate with the loss of glycemic control. Because the greatest effect was seen in patients who were being treated for T2DM, additional studies are needed to determine how best to incorporate psyllium into existing prevention and treatment algorithms with concomitant hypoglycemic medications.

Effects of distillers dried grains with solubles on amino acid, energy, and fiber digestibility and on hindgut fermentation of dietary fiber in a corn-soybean meal diet fed to growing pigs

The objective of this experiment was to measure the effect of distillers dried grains with solubles (DDGS) on the digestibility of AA, energy, and fiber, on the fermentation of fiber, and on the first appearance of digesta at the end of the ileum, in the cecum, and in the feces of growing pigs fed a corn-soybean meal-based diet. Sixteen pigs (initial BW = 38.0 +/- 1.6 kg) were prepared with a T-cannula in the distal ileum and a T-cannula in the cecum and allotted to 2 treatments. In period 1, all pigs were fed a corn-soybean meal diet. In periods 2, 3, and 4, pigs were fed the control diet or a diet containing corn, soybean meal, and 30% DDGS. First appearance of digesta at the end of the ileum, in the cecum, and over the entire intestinal tract was measured at the end of period 4. The apparent ileal digestibility (AID) and the apparent total tract digestibility (ATTD) of nutrients were measured, and the concentration of VFA was analyzed in ileal, cecal, and fecal samples. The AID of Lys (74.1%) in the DDGS diet was less (P < 0.05) than in the control diet (78.6%), but the AID of most other AA and GE, NDF, and total dietary fiber (TDF) were not different between the 2 diets. The ATTD of GE (81.0%), NDF (57.2%), TDF (55.5%), and DM (81.7%) were less (P < 0.05) in the DDGS diet than in the control diet (86.0, 69.3, 66.0, and 87.2%, respectively). The concentration of VFA in ileal, cecal, and fecal samples was not different between pigs fed the 2 diets. The pH of ileal and cecal digesta from pigs fed the DDGS diet (6.3 and 5.5) was greater (P < 0.01) than from pigs fed the control diet (5.8 and 5.3). The ATTD of DM, GE, ADF, NDF, and TDF did not change with collection period, but the AID of ADF, NDF, and TDF increased (P < 0.05) from period 2 to period 4. The concentration of all VFA, except isobutyrate, was greater (P < 0.05) in cecal samples from period 4 compared with period 2, and the concentration of all VFA except propionate and isovalerate were greater (P < 0.05) in fecal samples collected in period 4 compared with those collected in period 2. The first appearance of digesta at the end of the ileum, in the cecum, and in the feces was not affected by DDGS. In conclusion, pigs fed the diet containing DDGS had less digestibility of Lys, GE, ADF, NDF, and TDF than pigs fed the control diet. The digestibility of DM and GE was not influenced by collection period, but the concentration of VFA in cecal digesta and feces increased with the length of time pigs received the diets.

Glycemic and urinary volume responses in diabetic mellitus rats treated with Solanum lycocarpum

Dietary fiber performs important functions in diabetes mellitus control and treatment. In this study, we evaluate the reduction in plasma glucose after the treatment of diabetic rats with high-fiber Solanum lycocarpum flour. We found that serum glucose, water and food intake, urine excretion, and urine sodium concentration were reduced in S. lycocarpum flour-treated diabetic rats (TDRs), compared with diabetic control rats (DCRs). In addition, TDRs did not show signs of kidney hypertrophy, unlike those in the DCR group. These results suggest that the use of S. lycocarpum flour can be an effective support in diabetes mellitus treatment.

Reducing dietary fat from a meal increases the bioavailability of exogenous carbohydrate without altering plasma glucose concentration

The primary goal of this study was to determine the acute glycemic and endocrine responses to the reduction of fat content from a meal. On three separate occasions, nine overweight subjects (body mass index = 30 +/- 1 kg/m(2); 5 men, 4 women) consumed 1) a control meal ( approximately 800 kcal; 100 g of carbohydrate, 31 g of fat, and 30 g of protein), 2) a low-fat meal ( approximately 530 kcal; 100 g of carbohydrate, 1 g of fat, and 30 g of protein), or 3) a low-fat meal plus lipid infusion [same meal as low-fat meal, but the total energy provided was the same as control (800 kcal), with the "missing" fat ( approximately 30 g) provided via an intravenous lipid infusion]. All three meals contained [(13)C]glucose (3 mg/kg body wt) to assess the bioavailability of ingested glucose. During the 5-h period after each meal, we measured the recovery of [(13)C]glucose in plasma, plasma glucose, and insulin concentrations. We also measured plasma concentration of the gastrointestinal peptides: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and peptide YY(3-36) (PYY(3-36)). The recovery of the ingested [(13)C]glucose in the hour after ingestion was greater (P < 0.05) after the low-fat than after the control meal [area under the curve (AUC): 1,206 +/- 252 and 687 +/- 161 microM.h, respectively]. However, removing dietary fat from the meal did not affect the plasma concentration of glucose or insulin. Importantly, [(13)C]glucose recovery was not different during the low-fat and lipid infusion trials (AUC: 1,206 +/- 252 and 1,134 +/- 247 microM.h, respectively), indicating that the accelerated delivery of exogenous glucose found after removing fat from the meal is due exclusively to the reduction of fat in the gastrointestinal tract. In parallel with these findings, the reduction in fat calories from the meal reduced plasma concentration of GIP, GLP-1, and PYY(3-36). In summary, these data suggest that removing fat from the diet expedited exogenous glucose delivery into the systemic circulation and reduced the concentration of key gastrointestinal peptides, yet maintained plasma glucose concentration at control levels.

Concurrent duodenal manometric and impedance recording to evaluate the effects of hyoscine on motility and flow events, glucose absorption, and incretin release

Upper gastrointestinal motor function and incretin hormone secretion are major determinants of postprandial glycemia and insulinemia. However, the impact of small intestinal flow events on glucose absorption and incretin release is poorly defined. Intraluminal impedance monitoring is a novel technique that allows flow events to be quantified. Eight healthy volunteers were studied twice, in random order. A catheter incorporating six pairs of electrodes at 3-cm intervals, and six corresponding manometry sideholes, was positioned in the duodenum. Hyoscine butylbromide (20 mg) or saline was given as an intravenous bolus, followed by a continuous intravenous infusion of either hyoscine (20 mg/h) or saline over 60 min. Concurrently, glucose and 3-O-methylglucose (3-OMG) were infused into the proximal duodenum (3 kcal/min), with frequent blood sampling to measure glucose, 3-OMG, insulin, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). The frequency of duodenal pressure waves and propagated pressure wave sequences was reduced by hyoscine in the first 10 min (P<0.01 for both), but not after that time. In contrast, there were markedly fewer duodenal flow events throughout 60 min with hyoscine (P<0.005). Overall, blood glucose (P<0.01) and plasma 3-OMG concentrations (P<0.05) were lower during hyoscine than saline, whereas plasma insulin, GLP-1, and GIP concentrations were initially (t=20 min) lower during hyoscine (P<0.05). In conclusion, intraluminal impedance measurement may be more sensitive than manometry in demonstrating alterations in duodenal motor function. A reduction in the frequency of duodenal flow events is associated with a decreased rate of glucose absorption and incretin release in healthy subjects.

Net energy value of non-starch polysaccharide isolates (sugarbeet fibre and commercial inulin) and their impact on nutrient digestive utilization in healthy human subjects

The energy value of NSP has been expressed as their metabolizable energy (ME) content. The aim of the present study was to determine whether differences in ME and net energy (NE) contents were similar for insoluble and soluble NSP. Nine healthy young men were offered three diets according to a Latin-square design (3 × 3) with three repetitions: diet C (control), diet B (control + 50 g sugarbeet fibre/d) and diet I (control + 50 g commercial inulin/d). After a 16 d adaptation period to NSP isolate, food intake was controlled (duplicate meal method) and faeces and urine were collected for 8 d. A period of 60 h was devoted to measurement of energy expenditure (EE) by whole-body indirect calorimetry. NSP-isolate ingestion induced significant increases in the number of defecations and stool weight resulting from increases in water, DM and microbial mass excretion. After deduction of microbial N, differences in faecal N excretion between diets were not significantly different. Urinary N excretion was slightly decreased by sugarbeet fibre or commercial inulin ingestion but the N balances for the diets were not significantly different. Diet energy, N and lipid apparent digestibilities decreased by only 1–2 %. Commercial inulin was entirely fermented and fermentability of sugarbeet fibre averaged 0.886 (sd 0.117). Sugarbeet fibre and commercial inulin ME values averaged 10.7 (sd 1.2) and 13.0(sd 2.3) kJ/g DM respectively. NSP-isolate ingestion caused significant (sugarbeet) and nonsignificant (inulin) increases in daily EE. The maintenance NE contents of sugarbeet fibre and inulin averaged 5.0 (sd 5.0) and 11.9 (sd 1.3)kJ/g DM respectively. Differences in maintenance NE contents of NSP isolates were much greater than differences in ME values.

Upper gastrointestinal function and glycemic control in diabetes mellitus

Recent evidence has highlighted the impact of glycemic control on the incidence and progression of diabetic micro- and macrovascular complications, and on cardiovascular risk in the non-diabetic population. Postprandial blood glucose concentrations make a major contribution to overall glycemic control, and are determined in part by upper gastrointestinal function. Conversely, poor glycemic control has an acute, reversible effect on gastrointestinal motility. Insights into the mechanisms by which the gut contributes to glycemia have given rise to a number of novel dietary and pharmacological strategies designed to lower postprandial blood glucose concentrations.

Small bowel motility assessment with magnetic resonance imaging

PURPOSE

To assess primarily the feasibility of magnetic resonance imaging (MRI) as a tool to monitor small bowel peristaltic motion and secondarily to validate this technique by demonstrating drug-induced motility changes.

MATERIALS AND METHODS

After a standardized oral preparation of Ispaghula husk (Metamucil) and meglumine gadoterate (Gd-DOTA; Dotarem), 10 volunteers underwent dynamic MRI using a two-dimensional turbofast field echo (TFE) sequence with a slice repetition time of 500 msec. Intraluminal cross-sectional caliber changes over time were assessed allowing quantification of the peristaltic frequencies and amplitudes of the small gut on various regions of interest. Pharmacologically induced alterations of the peristaltic motion after spasmolytics and gastrokinetic motion enhancers were investigated.

RESULTS

Small bowel diameter measurement resulted in a peristalsis of 10.96 (SD = +/-2.51) waves per minute, oscillating regularly with mean amplitudes of 6.65 mm (SD = +/-1.15 mm). Peristaltic frequency in normal individuals is consistent with that observed with other techniques. Intravenous administration of scopolamine butylbromide (= hyoscine butylbromide/Buscopan) resulted in small bowel paralysis within 21.3 seconds (SD = +/-2.8 seconds). Prokinetic effect of intravenous metoclopramide (Paspertin) after Buscopan paralysis was tested in one volunteer, characterized by a slow recovery of peristalsis, which propagated from the proximal to the distal segments and enhanced contraction amplitudes.

CONCLUSION

Dynamic MRI allows observing and quantifying small bowel peristalsis, characterizing motion patterns, and monitoring the effects of interfering factors such as drugs.

Energy value of a low-digestible carbohydrate, NUTRIOSE FB, and its impact on magnesium, calcium and zinc apparent absorption and retention in healthy young men

BACKGROUND

Long-term consumption of imbalanced diets, poor in dietary fibres, resulted in the prevalence of several nutritional pathologies. However, low digestible carbohydrates (LDC) have many beneficial effects, especially on energy intake, digestive physiology, and mineral absorption.

AIM OF THE STUDY

To determine the digestive effects of a LDC, called NUTRIOSE FB, its metabolisable energy (ME) value, and its effects on mineral absorption in humans.

METHODS

Ten healthy young men were fed for 31 d periods a maintenance diet supplemented with either dextrose or the LDC at a level of 100 g DM/d, in six equal doses per d according to a cross-over design. After a 20 d adaptation period, food intake was determined for 11 days using the duplicate meal method, and faeces and urine were collected for 10 d for further analyses.

RESULTS

Ingestion of the LDC did not cause severe digestive disorders, except excessive gas emission, and flatulence and slight abdominal pain in some subjects for intakes above 50 g DM/d. Wet and dry stool outputs increased by 45 and 70%, respectively (P<0.02). In vitro enzymatic digestibility of the LDC was 15 (SD 1.5) %, and 9.2 (SD 8.3) % of the LDC was excreted in faeces (P<0.001). The ME value of the LDC was 14.1 (SD 2.3) kJ/g DM, that is 14 % less than the tabulated values of sucrose and starch. Its net energy value (NEV), estimated using three prediction equations, was 8.7, 8.9, and 11.4 kJ/g DM. Ingestion of the LDC significantly increased the relative apparent absorption of Mg, and Mg retention by 67% and 31 mg/d, respectively, tended to increase Ca apparent absorption (P=0.110) and Ca retention (P=0.059), but did not significantly alter Zn parameters.

CONCLUSION

NUTRIOSE FB can be used as a "bulking" agent, and substituted up to 50 g/d for usual maltodextrins without causing digestive disorders in healthy subjects. It would reduce intestinal transit disorders and energy intake, and improve magnesium and calcium absorption and retention.

Small bowel motility affects glucose absorption in a healthy man

OBJECTIVE

To investigate the relationship between duodenojejunal motor activity and glucose absorption and to evaluate the effect of modification of duodenojejunal motility on glucose absorption by using the prokinetic drug cisapride.

RESEARCH DESIGN AND METHODS

We examined seven healthy males, mean age 22 years, who were treated with cisapride 10 mg t.i.d. and placebo during 3 days in a randomized order, with a 2-week time interval. Duodenojejunal manometry was performed after each treatment on the morning of day 3, using an 18-lumen catheter. A liquid nutrient (3 kcal/min) was administered intraduodenally for 30 min, followed by a bolus of the glucose analog 3-O-methylglucose (3-OMG). Plasma 3-OMG concentrations were measured to assess absorption kinetics.

RESULTS

The area under the 3-OMG concentration curve in the first 30 min after infusion was related to the number of antegrade propagated pressure waves (r = 0.49, P < 0.05), but not to the peak concentration, time to peak, and absorption fraction. The mean amplitude of pressure waves was higher during cisapride than placebo (P < 0.05), but the reoccurrence of interdigestive motility, numbers of pressure waves, and propagated pressure waves, as well as 3-OMG absorption characteristics, were not significantly different between the two treatments. During both treatments >60% of antegrade propagated pressure waves were propagated over a very short distance (1.5 cm).

CONCLUSIONS

Glucose absorption in the human small intestine is related to short-traveling propagated intestinal contractile activity. Cisapride increases the amplitude of pressure waves, but does not affect the organization of pressure waves or the absorption of 3-OMG.

Net energy value of two low-digestible carbohydrates, Lycasin HBC and the hydrogenated polysaccharide fraction of Lycasin HBC in healthy human subjects and their impact on nutrient digestive utilization

The metabolizable energy content of low-digestible carbohydrates does not correspond with their true energy value. The aim of the present study was to determine the tolerance and effects of two polyols on digestion and energy expenditure in healthy men, as well as their digestible, metabolizable and net energy values. Nine healthy men were fed for 32 d periods a maintenance diet supplemented either with dextrose, Lycasin HBC (Roquette Frères, Lestrem, France), or the hydrogenated polysaccharide fraction of Lycasin HBC, at a level of 100 g DM/d in six equal doses per d according to a 3 x 3 Latin square design with three repetitions. After a 20 d progressive adaptation period, food intake was determined for 12d using the duplicate meal method and faeces and urine were collected for 10 d for further analyses. Subjects spent 36 h in one of two open-circuit whole-body calorimeters with measurements during the last 24h. Ingestion of the polyols did not cause severe digestive disorders, except excessive gas emission, and flatulence and gurgling in some subjects. The polyols induced significant increases in wet (+45 and +66% respectively, P<0.01) and dry (+53 and +75 % respectively, P<0.002) stool weight, resulting in a 2% decrease in dietary energy digestibility (P<0.001). They resulted also in significant increases in sleeping (+4.1%, P<0.03) and daily energy expenditure (+2.7 and +2.9% respectively, P<0.02) compared with dextrose ingestion. The apparent energy digestibility of the two polyols was 0.82 and 0.79 respectively, their metabolizable energy value averaged 14.1 kJ/g DM, and their net energy value averaged 10.8 kJ/g DM, that is, 35 % less than those of sucrose and starch.

Relationships of upper gastrointestinal motor and sensory function with glycemic control

Acute changes in the blood glucose concentration have a major reversible effect on esophageal, gastric, intestinal, gallbladder, and anorectal motility in both healthy subjects and diabetic patients. For example, gastric emptying is slower during hyperglycemia than euglycemia and accelerated during hypoglycemia. Acute hyperglycemia also affects perceptions arising from the gastrointestinal tract and may accordingly, be important in the etiology of gastrointestinal symptoms in diabetes. Elevations in blood glucose that are within the normal postprandial range also affect gastrointestinal motor and sensory function. Upper gastrointestinal motor function is a critical determinant of postprandial blood glucose concentrations by influencing the absorption of ingested nutrients. Interventions that reduce postprandial hyperglycemia, by modulating the rate of gastric emptying, have the potential to become mainstream therapies in the treatment of diabetes.

Arabinoxylan fiber, a byproduct of wheat flour processing, reduces the postprandial glucose response in normoglycemic subjects

BACKGROUND

Arabinoxylan (AX) is the major component of dietary fiber in the cereal grains that make up a large proportion of our diet. However, the physiologic effect of AX is unknown.

OBJECTIVE

The objective of this study was to determine whether AX improves postprandial glucose and insulin responses in healthy humans.

DESIGN

AX-rich fiber was extracted from the byproduct of wheat-flour processing. Three isoenergic breakfasts, comprising bread, margarine, and jam, had 75 g available carbohydrate, 10 g protein, and 14 g fat and contained 0, 6, and 12 g AX-rich fiber, respectively. Fourteen healthy subjects consumed the 3 breakfast meals in random order on 3 mornings >/=3 d apart after an overnight fast. Blood was taken from the subjects at regular intervals over 2 h and was analyzed for glucose and insulin. The palatability of bread containing AX-rich fiber was compared with that of a control bread.

RESULTS

Compared with the control meal containing 0 g AX-rich fiber, the peak postprandial glucose concentration after meals containing 6 and 12 g AX-rich fiber was significantly lower (6. 3 +/- 1.3 compared with 7.2 +/- 1.0 mmol/L, P < 0.01; 5.9 +/- 0.9 compared with 7.2 +/- 1.0 mmol/L, P < 0.001, respectively). The incremental area under the curve (IAUC) for glucose was 20.2% (95% CI: 5.8%, 34.7%; P < 0.01) and 41.4% (25.9%, 56.8%; P < 0.001) lower, whereas IAUC for insulin was 17.0% (2.0%, 32.1%; P < 0.05) and 32. 7% (18.8%, 46.6%; P < 0.001) lower, respectively. Bread containing AX-rich fiber was as pala as 50% whole-wheat bread when evaluated with sensory analysis by 30 volunteers.

CONCLUSIONS

Postprandial glucose and insulin responses were improved by ingestion of AX-rich fiber. Further research is required to determine whether AX-rich fiber is of benefit to people with type 2 diabetes.

Fructo-oligosaccharide supplementation: effects on metabolic, endocrine and hematological traits in veal calves

Fructo-oligosaccharides (FOS) are soluble fibres which exert various effects in the gastrointestinal tract, and induce metabolic and endocrine changes. The effects are favourable in diabetes mellitus, and may be favourable in veal calves, which during late periods of fattening often develop hyperglycemia, glucosuria and insulin resistance, especially during high lactose intake. Based on this we have studied metabolic, endocrine and haematological traits in veal calves (Simmental x Red Holstein) fed FOS (10 g/day; group GrF) or no FOS (group GrC). Whole milk and milk replacer in both groups, on a kg body weight basis, were fed in identical amounts. Experiments, lasting for 3 weeks, started when calves were 10 weeks old and weighed 117 kg. During week 3 lactose was supplemented to enhance post-absorptive glucose loads. Feed intakes were similar in both groups, but weight gain tended to be higher in GrF than GrC. The post-prandial increase of glucose concentrations was significantly smaller, of lactate tended to be smaller, and growth hormone peak frequency tended to be lower, whereas maximal insulin concentrations reached post-prandially were significantly higher in GrF than GrC. Eosinophil granulocytes increased during FOS feeding. In conclusion, FOS had basically similar effects on metabolic and endocrine traits in veal calves as in animals and humans with diabetes mellitus, but changes were small, albeit more prominent after lactose loads.

Functional food properties of non-digestible oligosaccharides: a consensus report from the ENDO project (DGXII AIRII-CT94-1095)

This paper results from the final phase of the ENDO project (DGXII AIRII-CT94-1095), a European Commission-funded project on non-digestible oligosaccharides (NDO). All participants in the programme met to perform a consensus exercise on the possible functional food properties of NDO. Topics studied during the project (including a workshop on probiotics and prebiotics) and related aspects, for which considerable evidence has been generated recently, were evaluated on the basis of existing published scientific evidence. There was a general consensus that: (1) there is strong evidence for a prebiotic effect of NDO in human subjects. A prebiotic effect was defined as a food-induced increase in numbers and/or activity predominantly of bifidobacteria and lactic acid bacteria in the human large intestine; (2) there is strong evidence for the impact that NDO have on bowel habit; (3) there is promising evidence that consumption of inulin-type fructans may result in increased Ca absorption in man; (4) there are preliminary indications that inulin-type fructans interact with the functioning of lipid metabolism; (5) there is preliminary evidence in experimental animals of a preventive effect against colon cancer. Human nutrition studies are needed to substantiate these findings. It was concluded that the nutritional properties of NDO may prove to be a key issue in nutritional research in the future.

The influence of sugar-beet fibre, guar gum and inulin on nutrient digestibility, water consumption and plasma metabolites in healthy Beagle dogs

The aim of the present study was to evaluate the effects of three fibres (sugar-beet fibre, guar gum and inulin) incorporated in the basal diet of healthy dogs at 7 per cent of dry matter (DM). Parameters examined included stool output, water consumption, nutrient digestibility and fasting and postprandial plasma metabolites. All fibres increased wet faecal output; an increase in faecal DM output being observed with sugar-beet fibre only. Sugar-beet fibre and inulin increased daily water consumption. Sugar-beet fibre and guar gum decreased DM digestibility. The three fibres diminished organic matter and crude protein digestibility while ether extract digestibility was decreased by guar gum and inulin. Guar gum induced lower postprandial insulin, alpha-amino-nitrogen and urea plasma concentrations. Guar gum also lowered fasting cholesterolaemia. Sugar-beet fibre and inulin showed no metabolic effects. These physiological properties suggest that guar gum would be a suitable ingredient for dietary therapy of chronic diseases such as diabetes mellitus or hyperlipidaemia in the dog.

Digestive and metabolic effects of potato and maize fibres in human subjects

The physiological effects of dietary fibres in humans are due to their physico-chemical properties. However, it is difficult to predict these effects simply by measuring certain characteristics in vitro. Studies in human subjects are still required to assess the effectiveness of new substrates. The aim of the present study in healthy human subjects was to evaluate the effects of two novel fibres, potato (PF) and maize (MF), on fasting and postprandial blood concentrations of carbohydrate and lipid metabolites as well as on stool output and transit time. The chemical composition, water-binding capacity (WBC) and fermentative properties of the fibres were also characterized in order to determine their possible involvement in digestive and metabolic effects. Stools, as well as breath and blood samples, were collected after consumption for 1 month of either a basal diet (control) or a basal diet supplemented with fibre (15 g/d). MF resisted fermentation better than PF and had lower digestibility. However, both fibres increased faecal output of dry matter, neutral sugars and water. There was an inverse relationship between stool weight and orofaecal transit time, although only MF significantly reduced transit time. Orocaecal transit was lengthened by PF, probably because of its high WBC. PF ingestion also decreased postprandial plasma levels of total and esterified cholesterol but had no effect on fasting concentrations. In contrast, MF lowered fasting cholesterolaemia and increased free:esterified cholesterol. These particular physiological and fermentative properties suggest that PF and MF would be suitable ingredients in a healthy diet.

Emulsification and lipolysis of triacylglycerols are altered by viscous soluble dietary fibres in acidic gastric medium in vitro

This in vitro study was designed to test the hypothesis that soluble dietary fibres can alter the process of intragastric lipid emulsification and possibly subsequent triacylglycerol lipolysis. Three guar gums, two pectins and gum arabic were dissolved in acidic gastric medium in the concentration range 0.3-2.0% (w/v). Viscosities of fibre solutions were measured and apparent viscosities varied over a wide range (0.7-77 mPa/s). Emulsification of a lipid mixture (triolein/phosphatidylcholine/cholesterol) was performed under mild conditions in the presence of increasing concentrations of soluble fibres. The amount of emulsified lipid was not affected whereas the size of the emulsified droplets was increased by raising the concentration of viscous fibres only. The droplet size (r=0.75, P=0.006) and overall droplet surface area (r=-0.69, P=0.009) were strongly correlated with the medium viscosity in the range 0-20 mPa/s. The addition of solutions of viscous fibres to a preformed standard emulsion did not change the initial velocity of human gastric lipase reaction. Conversely, when emulsions prepared in the presence of fibres (i.e. with different droplet sizes) were incubated with excess gastric enzyme for 2 h, the high-viscosity guar gum significantly reduced the extent of triacylglycerol lipolysis, as compared with control and low- or medium-viscosity fibres. In conclusion, the data obtained show that reducing emulsification of dietary lipids in the mildly acid medium found in the stomach is a mechanism by which soluble viscous fibres can alter lipid assimilation.