Depression of the glycemic index by high levels of beta-glucan fiber in two functional foods tested in type 2 diabetes.

OBJECTIVES: To determine the extent to which beta-glucan reduces the glycemic index (GI) of oat products and whether high levels of beta-glucan impair palatability. DESIGN: The study design was an open-label, randomized cross-over study with six treatment segments. SETTING: Free-living outpatients. SUBJECTS: Sixteen volunteers with type 2 diabetes (10 men, six women, 61+/-2 y, body mass index 29+/-2 kg/m(2), HbA1c 7.4+/-0.4%) were recruited from the St Michael's Hospital diabetes clinic. INTERVENTIONS: Volunteers were given, in random order, 50 g available carbohydrate portions of: white bread; a commercial oat bran breakfast cereal (4.4 g% beta-glucan); and a prototype beta-glucan-enriched breakfast cereal and bar, both high in beta-glucan (8.1 and 6.5 g% beta-glucan, respectively) and sweetened with fructose. Capillary blood samples were taken fasting and then 30, 60, 90, 120, 150 and 180 min after the start of the meal. Palatability was recorded using two different methods. RESULTS: The glycemic indices of the prototype beta-glucan cereal (mean+/-s.e.m.; 52+/-5) and beta-glucan bar (43+/-4.1) were significantly lower than the commercial oat bran breakfast cereal (86+/-6) and white bread (100; P<0.05). All foods were highly palatable and not significantly different. It was found that the GI of the test foods used in this study decreased by 4.0+/-0.2 units per gram of beta-glucan compared to our estimate of 3.8+/-0.6 for studies reported in the literature. CONCLUSION: Addition of beta-glucan predictably reduces the GI while maintaining palatability. In a 50 g carbohydrate portion each gram of beta-glucan reduces the GI by 4 units, making it a useful functional food component for reducing postprandial glycemia. SPONSORSHIP: Nestec, Switzerland.

Colonic bacterial activity and serum lipid risk factors for cardiovascular disease.

Antibiotics are being proposed for the treatment of cardiovascular disease. In the past, antibiotics were advocated for the control of hypercholesterolemia. We have therefore investigated the relation between colonic bacterial activity and serum lipids. In a four-phase randomized crossover study, we fed a different starch supplement during each 2-week phase to 24 healthy subjects. In two phases, supplements containing resistant starches were fed that reach the colon and are largely fermented by colonic bacteria. Fecal starch recovery therefore reflects the metabolic activity of colonic microflora. The control treatments were conventional starches. Blood lipid levels were obtained at the start and 4-day fecal collections at the end of each phase. Resistant starch supplements increased fecal starch excretion by 3.8 +/- 1.2 g/d more than conventional starches (P = .006). Mean starch excretion was related positively to pretreatment serum high-density lipoprotein (HDL) cholesterol (r = -.57, P = .003) and negatively to low-density lipoprotein (LDL) cholesterol (r = -.57, P = .004), apolipoprotein B:AI (r = -.56, P = .005), and fecal output of fusobacteria (r = -.73, P = .003) and bacteroides (r = -.72, P = .003). The ratio of fusobacteria to total anaerobes was also related to pretreatment LDL cholesterol (r = .56, P = .037). Differences in starch excretion between healthy subjects, as a measure of bacterial activity, accounted for 32% of the variation in pretreatment LDL cholesterol. The activity of colonic microflora therefore appears to influence serum lipid levels. Alterations of bacterial number and activity may provide an additional strategy to control serum lipid risk factors for cardiovascular disease.

Physiological effects of resistant starches on fecal bulk, short chain fatty acids, blood lipids and glycemic index.

OBJECTIVE: To assess the effects on fecal bulking, fecal short chain fatty acid (SCFA) production, blood lipids and glycemic indices of two different forms of resistant starch (RS2 and RS3) from a high-amylose cornstarch. METHODS: Twenty-four healthy subjects (12 men; 12 women) consumed four supplements taken for 2 weeks in random order separated by 2-week washout periods. The supplements were a low-fiber (control) and supplements providing an additional 30 g dietary fiber as wheat bran (high-fiber control) or the equivalent amount of resistant starch analyzed gravimetrically as dietary fiber from RS2 or RS3. Four-day fecal collections and 12-hour breath gas collections were obtained at the end of each period. Fasting blood was taken at the beginning and end of each period. Glycemic indices of supplements were also assessed. RESULTS: The wheat bran supplement increased fecal bulk 96+/-14 g/day compared with the low-fiber control (p<0.001) with the mean for both resistant starches also being greater (22+/-8 g/day) than the low-fiber control (p=0.013). On the resistant starch phases, the mean fecal butyrate:SCFA ratio, which has been suggested to have positive implications for colonic health, was significantly above the low-fiber control by 31+/-14% (p=0.035). Resistant starches did not alter serum lipids, urea or breath H2 or CH4. No significant differences in glycemic index were seen between the RS and control supplements. CONCLUSION: The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.

The role of viscous soluble fiber in the metabolic control of diabetes. A review with special emphasis on cereals rich in beta-glucan.

Recent recommendations for the dietary management of diabetes mellitus state that diet needs to be individualized so that there is improved glucose and lipid control in the patient. In a majority of individuals with diabetes, this is best done with a diet that is low in fat and high in carbohydrate, particularly that of cereal origin. However, symptoms of hyper- and hypoglycemia must be averted. Most cereal products, however, tend to have a high glycemic index Cereals such as Prowashonupana barley or fractions of oat bran are particularly high in the soluble fiber beta-glucan, which when taken with a meal increases the viscosity of the meal bolus once it has reached the small intestine, where the absorption of nutrients occurs. This high viscosity delays absorption. A 50% reduction in glycemic peak can be achieved with a concentration of 10% beta-glucan in a cereal food. A significant lowering of plasma LDL cholesterol concentrations can also be anticipated with the daily consumption of > or = 3 g of beta-glucan. Diabetic individuals can benefit from diets that are high in beta-glucan, which, as a component of oats and barley, can be incorporated into breakfast cereals and other products.

Effects of breakfast cereals containing various amounts of beta-glucan fibers on plasma glucose and insulin responses in NIDDM subjects.

OBJECTIVE: To determine whether increasing doses (amounts) of beta-glucan present in an extruded breakfast cereal affect the glycemic and insulinemic responses in eight NIDDM subjects, compared with the same responses after a continental breakfast (bread, milk, cheese, ham). RESEARCH DESIGN AND METHODS: Breakfast cereals were produced using various proportions of oat bran enriched in fiber, which contain an unusually high amount of a viscous polysaccharide, called beta-glucan, and oat bran. The carbohydrate load was 35 g. RESULTS: The maximum increases observed in plasma glucose after the breakfast cereal were 67% (P < 0.05), 42% (P < 0.001), and 38% (P < 0.001) with 4.0, 6.0, and 8.4 g beta-glucan, respectively, compared with the continental breakfast. There was a linear inverse relationship between dose of beta-glucan and plasma glucose peak or area under the glucose curve (R2 = 0.94, P < 0.05). Postprandial insulin increase was only 59-67% (P < 0.01) as high as the continental breakfast after all three levels of beta-glucan. CONCLUSIONS: The 50% decrease in glycemic response that was observed after the ingestion of 35 g carbohydrate is estimated to occur with approximately 5 g beta-glucan. This dose of beta-glucan can easily be attained without the loss of taste by incorporating oat bran concentrate in products.

Digestion and absorption of sorbitol, maltitol and isomalt from the small bowel. A study in ileostomy subjects.

OBJECTIVE: To quantify small bowel digestion and absorption of sorbitol, isomalt and maltitol in ileostomy patients and estimate the metabolizable energy. SUBJECTS: Study A: Nine ileostomy patients, under a constant controlled diet, ate during three consecutive days 2 milk chocolate bars per day, containing 2 x 15 g of polyol, each day with another polyol in random order. The first bar was taken 30 min after breakfast, and the second bar, 7 h after breakfast. Effluents were recovered during the whole study. Study B: 5, 10 or 20 g of sorbitol or isomalt were consumed each day in a drink during two 3-day periods by two ileostomy subjects. The recovery in the ileal effluent was measured over 24 h. RESULTS: Study A: Carbohydrate recovery in ileostomy effluent was 26.8 +/- 2.8% (mean+SEM) for sorbitol, 24.8 + 5.7% for maltitol (2/3 as sorbitol) and 40.0 +/- 0.7% for isomalt (1/3 being sorbitol and mannitol). Ileal excretion, compared with a day without polyol, was compared in 4 subjects. The total volume excreted, as well as dry matter increased after polyol consumption. When taking this extra loss into account, the metabolizable energy value of the polyols for 2 x 15 g intake were: sorbitol, 12 kJ/g (2.8 kcal/g); maltitol, 13 kJ/g (3.1 kcal/g); isomalt, 9 kJ/g (2.1 kcal/g). Study B: The level of digestion and absorption of both sugar alcohols was dose dependent. CONCLUSIONS: These results indicate that sorbitol, maltitol and isomalt are rather extensively absorbed, but the digestibility of the other nutrients is also reduced, due to the osmotic load caused by the polyols in the small intestine. There are evidences of a dose dependency of the energy value of the polyols.

Carbohydrate foods with specific nutritional properties--a challenge to the food industry.

About 80% of the food consumed in the developed countries is processed by the food industry and 40% of this food is consumed outside the home. The food industry can therefore play a major role in helping the consumer to eat wisely by offering carbohydrate-rich foods, which can help reduce excess energy intake, improve diabetes control, and reduce dental caries. In many foods, fat has been reduced, dietary fiber increased, and sugar decreased; this has often been achieved by using carbohydrate ingredients and appropriate technology without decreasing the sensory quality of the foods.

Inhibition of amylopectin retrogradation by partial beta-amylolysis.

The rate of retrogradation of amylopectin solution differs from one starch variety to another and it is thought to be due to the different length of the external chains of amylopectin. A shortening of the external chains of waxy maize and potato amylopectin was performed with beta-amylase. Partial beta-amylolysis produced a significant fraction of chains having 2-6 glucose units. A high linear correlation (R > 0.97) was found between the enthalpy of retrograded amylopectin measured by DSC, or percent solid measured by low frequency pulsed NMR, and average external chain length. No retrogradation appeared to occur when the external chains of both amylopectins had 11 or less glucose units on average. The inhibition of retrogradation appears to be caused primarily by the presence of very short external chains, which hinders the reassociation of the long external chains.

Influence of sterilization, drying and oat bran enrichment of pasta on glucose and insulin responses in healthy subjects and on the rate and extent of in vitro starch digestion.

The effects of sterilization and oat bran enrichment of pasta on the glucose and insulin responses in healthy subjects were evaluated. Cooked and canned spaghetti and cooked fettucini without and with enrichment with oat bran (28%) were compared. Further, the effects of various low- and high-temperature drying conditions for spaghetti, cooking time and sterilization on the starch digestion rate and content of enzyme-resistant starch (RS) in vitro were also studied. Various cooking quality data were also determined to allow interpretation of results. The incremental glucose area (0-120 min) produced by canned spaghetti was twice the area of that produced by cooked spaghetti (69.03 vs 35.45 mmol/l x min, P less than 0.01). The incremental insulin area (0-120 min) was also significantly higher with canned spaghetti (17,500 vs 12,600 pmol/l x min, P less than 0.05). The rapid digestion was caused by excessive swelling of starch during sterilization that promoted a very soft texture of the spaghetti. Enrichment of fettucini with oat bran reduced slightly the incremental insulin area (15,600 vs 20,100 pmol/l x min, P less than 0.05, for 0-120 min), but did not significantly reduce the glucose area. Drying conditions and cooking times could be varied within broad limits without affecting the rate of starch digestion in vitro of cooked spaghetti. In sterilized spaghetti the content of resistant starch was higher than that found in cooked 'al dente' spaghetti (2.2-3.4 vs 0.5 mg/100 mg total starch). In conclusion, sterilization influences the nutritional properties of starch in pasta by substantially increasing the glucose and insulin responses and by formation of resistant starch. The effect of oatbran environment is restricted mainly to a slight decrease in the insulin response.

The effect of muesli or cornflakes at breakfast on carbohydrate metabolism in type 2 diabetic patients.

Fourteen overweight insulin-treated type 2 diabetic patients ate a breakfast, consisting of either muesli (slow release starch: SRS) or cornflakes (fast release starch: FRS), in either case with milk (46 g carbohydrate), during two consecutive randomized crossover periods of two weeks. The rest of the diet remained unchanged. At the end of each period the patients underwent a glucose tolerance test after an overnight fast without their usual evening insulin injection. Both mean plasma glucose responses curves were identical after the two dietary periods, but plasma insulin was significantly lower at zero (-17%, P less than 0.05) and 2 h (-21%, P less than 0.05) at the end of the muesli (SRS) period as compared to the cornflakes (FRS) period. The mean day-long plasma glucose level (four measurements) at the end of the muesli period was 21% (P = 0.023) lower than after the cornflakes period. These results show that switching, at breakfast only, from standard cereals to slow release starch cereals improves the carbohydrate metabolism of diabetic patients. In addition, the fact that diabetic patients could reduce their insulin requirement (P less than 0.05) with concomitant reduction of their daily blood glucose level implies that sensitivity to insulin was improved by slow release starct foods consumed at breakfast.

The physiological and nutritional importance of dietary fibre.

Fibrous material is an integral part of the daily diet, and it exerts direct physiological effects throughout the gastrointestinal tract, in addition to affecting metabolic activities more indirectly. The interplay of these effects is responsible for the presumed desirable influence of fibre on weight regulation, carbohydrate and lipid metabolism, and on colon function. Numerous mechanisms of action have been identified which are related to the type and the physicochemical nature of the fibre. This review concentrates mainly on the serum cholesterol-lowering effect of dietary fibre, its colonic fermentation, and finally on some possible adverse effects that one should be aware of when consuming high amounts of dietary fibre.

Metabolism of maltitol by conventional rats and mice and germ-free mice, and comparative digestibility between maltitol and sorbitol in germ-free mice.

The metabolism of maltitol (4-alpha-D-glucosylsorbitol) was assessed in fasting conventional (C) rats, C mice and germ-free (GF) mice, using [U-14C]maltitol. The radiorespirometric patterns of 14CO2 collected for 48 h after the administration of labelled maltitol were characterized by a constant rate of 14CO2 production lasting 4 h for both C rats and mice. The pattern for the GF mice showed a peak at the second hour followed immediately by a slow decrease. The percentage recovery of 14CO2 was significantly lower for the GF mice (59%) compared with C animals (72-74%). Urine, faeces and intestinal contents after 48 h totalled 19% of the administered radioactivity in the C rats and mice and 39% in the GF mice. The digestibility of maltitol and the absorption of sorbitol in GF mice was also assessed. The caecum and small intestine of GF mice, 3 h after administration of equimolar quantities of maltitol (140 mg/kg body-weight) or sorbitol (70 mg/kg body-weight), contained 39 and 51% of the ingested dose respectively, present mostly in the caecum as sorbitol. The alpha-glucosidase (maltase) (EC3.2.1.20) activity of the small intestine was appreciably higher (1.5-1.7 times) in the GF mice than in the C mice. These results suggest that the enzymic activities in the small intestine of mice and rats are sufficient to hydrolyse maltitol extensively. Consequently, the slow absorption of sorbitol seems to be an important factor limiting the overall assimilation of maltitol in the small intestine.

Gastric emptying and glycemic response after ingestion of mashed bean or potato flakes in composite meals.

Two meals of mashed-bean or potato flakes and meat were served in random order to six healthy male subjects to determine effects on gastric emptying and glycemic reactions. The meals had comparable physical appearance and contained similar amounts of digestible carbohydrate, fat, and protein. No difference in gastric emptying, recorded by gamma camera after mixing 51Cr with the meals, was found between the meals. The bean-flakes meal gave significantly lower blood glucose (p less than 0.01) and serum insulin (p less than 0.05) concentrations than did the potato-flakes meal. The overall blood glucose response, calculated as incremental area under the curves for 2 h, also differed between the meals (p less than 0.05) whereas the overall insulin response did not differ significantly. The low glycemic response after bean flakes could not be explained by the gastric emptying rate, which provides additional evidence for the slow digestion of bean starch in the small intestine.

Hydrogen excretion after ingestion of five different sugar alcohols and lactulose.

The breath hydrogen excretion was measured for 5 h after the initial rise on seven subjects who consumed randomly, and after 5 d of adaptation, equimolar amounts of sorbitol (10 g), mannitol (10 g), maltitol (19 g), Palatinit (19 g anhydrous), lactitol (19 g anhydrous), lactulose (19 g) in aqueous solution. The mean mouth-to-caecum transit time was 1.5 h, which was not significantly different from one carbohydrate to another, but varied significantly from one subject to another (0.7-2.4 h). Suprabasal increment of breath hydrogen after lactitol was significantly higher than that from the other polyols (P less than 0.001) over 5 h. Lactitol and lactulose, which are known to be totally undigested in the small intestine, gave the highest mean incremental area under the breath hydrogen curve, 327 p.p.m. H2 over 5 h and 224 p.p.m. H2 over 5 h, respectively. The values for the other test compounds ranged from 145 to 209 p.p.m. H2 over 5 h, which suggest that there had been only partial absorption in the small intestine.

Tannin-rich carob pod for the treatment of acute-onset diarrhea.

Infants aged 3-21 months with acute diarrhea of bacterial and viral origin were treated as inpatients with oral rehydration fluid and randomly received for up to 6 days either a tannin-rich carob pod powder (40% tannins or 21.2% polyphenols and 26.4% dietary fiber), 1.5 g/kg/day (n = 21) to a maximum of 15 g, or an equivalent placebo (n = 20). The duration of the diarrhea from admission was 2.0 +/- 0.27 days in the test group and 3.75 +/- 0.30 days in the placebo group (p less than 0.001). Normalized defecation, body temperature, and weight and cessation of vomiting were reached more quickly by the patients who received the test substance. The test substance was well accepted and tolerated.

Metabolic effects of instant bean and potato over 6 hours.

For 7 d six volunteers consumed at breakfast a 50-g starch meal prepared from either potato-flakes bran or instant bean flakes. These meals were isocaloric and had the same analytical composition. The metabolic effect of the meals on plasma glucose and insulin levels and on energy expenditure were assessed over 6 h on days 1 and 7 of each diet period. No significant differences in the shape and magnitude of plasma glucose and insulin responses were observed between days 1 and 7 of the same diet. Maximum glucose and insulin responses were significantly lower after the bean meal than after the potato meal. Although each meal tested was digested at a different rate, substrate oxidation and energy expenditure over 6 h were very similar.

Comparison of metabolic effects of white beans processed into two different physical forms.

In the present study eight control subjects and eight patients with non-insulin-dependent diabetes mellitus (NIDDM) consumed single portions of processed beans equivalent to 50 g of carbohydrate. The beans were processed by different methods into two physical forms; one maintained the integrity of the bean cells (undamaged bean cells, UC) and the other ruptured the bean cells (damaged bean cells, DC). Incremental glucose response areas after ingestion of either UC or DC were not significantly different in control subjects, while incremental insulin response areas (49 +/- 7 vs. 26 +/- 4 microU X ml-1 X h-1, P less than .05) were significantly lower after eating UC-processed beans. In patients with NIDDM both incremental glucose (150 +/- 14 vs. 73 +/- 25 mg X dl-1 X h-1, P less than .001) and insulin (67 +/- 16 vs. 46 +/- 11 microU X ml-1 X h-1, P less than .05) response areas were significantly lower after UC administration. To test the effectiveness of the UC-processed bean when incorporated into mixed meals, nine patients with NIDDM consumed mixed meals containing either DC or UC on two separate mornings. The test meals represented a typical Mexican American use of pureed beans wrapped in a flour tortilla topped with melted cheese. Incremental glucose responses were significantly lower after the UC meal (171 +/- 42 mg X dl-1 X h-1, P less than .05) when compared with the DC meal (212 +/- 34 mg X dl-1 X h-1). Incremental insulin areas were also lower after the UC (91 +/- 19 microU X ml-1 X h-1) when compared with the DC meal (120 +/- 22 microU X ml-1 X h-1).(ABSTRACT TRUNCATED AT 250 WORDS)