Gastrointestinal responses following acute and medium term intake of retrograded resistant maltodextrins, classified as type 3 resistant starch

DESIGN

Study part 1 was executed as a randomized double-blind placebo-controlled crossover study and study part 2 as a longitudinal study.

SUBJECTS

Forty-one healthy adult volunteers aged 18-24 years were recruited from the student population of the University of Salford. All subjects enrolled and completed study part 1 and 39 subjects enrolled and completed study part 2.

INTERVENTIONS

In study part 1, individuals consumed, in random order 0, 20, 40, 60, 80, 100 or 120 g of a RRM containing starch product incorporated in pre-prepared foods on individual test days. Assuming a minimum content of 50% RRM in the starch product this delivered respectively 0, 10, 20, 30, 40, 50 or 60 g of RRM. All foods were prepared and coded by personnel not involved in carrying out the tests. Test days were separated by 7 day washout periods. In study part 2, consumption of RRM was increased from 3.6 g at day 1 in incremental doses up to each subject's MNED as determined in study 1, to be achieved at day 14. Subsequently, RRM intake was from day 15-21 in a way that the final intake at day 21 was at least 10 g above the individual MNED. In both parts of the study, subjects reported the prevalence and magnitude of GI symptoms.

RESULTS

No significant change was observed in either defecation frequency and faecal consistency or the number of subjects experiencing any GI symptoms, following consumption of foods containing 0-60 g RRM. The individual MNED at which an increase in symptoms did not occur was determined as 60 g RRM for 71% of the subjects who participated in study part 1. Regression analysis showed that consumption of gradually increasing doses of RRM in food products over 21 days was associated with a significant increase in the mean symptom score for flatulence (P=1.5 x 10(-4)), total bowel movement frequency (P=0.023) and bowel movement frequency to pass watery faeces (P=0.0157). Increasing the ingested dose of RRM by 10 g above the predetermined MNED, however, did not provoke significant increases in GI symptoms. In both studies, the majority of symptom responses were classified by the subjects as 'little more than usual'.

CONCLUSIONS

Consumption of up to 60 g RRM is tolerated well by most individuals with no evidence of any significant dose-dependent increase in the magnitude of symptoms or the occurrence of multiple GI symptoms. However, a mild laxative effect when consuming >60 g RRM is suggested. Although there was no change in GI responses following consumption of increasing doses of RRM over 21 days, generally a dose of 10 g RRM above the MNED level was tolerated well during medium term intake.

Gastrointestinal tolerance of erythritol and xylitol ingested in a liquid

OBJECTIVES

To determine and compare the gastrointestinal (GI) responses of young adults following consumption of 45 g sucrose, 20, 35 and 50 g xylitol or erythritol given as a single oral, bolus dose in a liquid.

DESIGN

The study was a randomized, double-blind, placebo-controlled study.

SUBJECTS

Seventy healthy adult volunteers aged 18-24 years were recruited from the student population of the University of Salford. Sixty-four subjects completed the study.

INTERVENTIONS

Subjects consumed at home without supervision and in random order, either 45 g sucrose or 20, 35 and 50 g erythritol or xylitol in water on individual test days, while maintaining their normal diet. Test days were separated by 7-day washout periods. Subjects reported the prevalence and magnitude of flatulence, borborygmi, bloating, colic, bowel movements and the passage of faeces of an abnormally watery consistency.

RESULTS

Compared with 45 g sucrose, consumption of a single oral, bolus dose of 50 g xylitol in water significantly increased the number of subjects reporting nausea (P<0.01), bloating (P<0.05), borborygmi (P<0.005), colic (P<0.05), watery faeces (P<0.05) and total bowel movement frequency (P<0.01). Also 35 g of xylitol increased significantly bowel movement frequency to pass watery faeces (P<0.05). In contrast, 50 g erythritol only significantly increased the number of subjects reporting nausea (P<0.01) and borborygmi (P<0.05). Lower doses of 20 and 35 g erythritol did not provoke a significant increase in GI symptoms. At all levels of intake, xylitol produced significantly more watery faeces than erythritol: resp. 50 g xylitol vs 35 g erythritol (P<0.001), 50 g xylitol vs 20 g erythritol (P<0.001) and 35 g xylitol vs 20 g erythritol (P<0.05).

CONCLUSIONS

When consumed in water, 35 and 50 g xylitol was associated with significant intestinal symptom scores and watery faeces, compared to the sucrose control, whereas at all levels studied erythritol scored significantly less symptoms. Consumption of 20 and 35 g erythritol by healthy volunteers, in a liquid, is tolerated well, without any symptoms. At the highest level of erythritol intake (50 g), only a significant increase in borborygmi and nausea was observed, whereas xylitol intake at this level induced a significant increase in watery faeces.

Effects of short-chain fructo-oligosaccharides on glucose and lipid metabolism in mild hypercholesterolaemic individuals

BACKGROUND

The intake of 10 g/day of short-chain-fructo-oligosaccharides (sc-FOS) has been shown to increase significantly bifidus counts and to produce high amounts of short-chain fatty acids (SCFA), presumed to influence glucose and lipid metabolism.

AIM

To evaluate the effects of moderate intake of sc-FOS on glucose and lipid metabolism in individuals with mild hypercholesterolaemia.

DESIGN

A randomized double-blind sequential cross-over study.

SUBJECTS AND METHODS

Thirty subjects of both genders (20 M/10 F), mean age 45.5+/-9.9 years (M+/-SD), BMI 26.6+/-2.2 kg/m(2), with plasma cholesterol >5.17 and <7.76 mmol/l and plasma triglycerides <3.45 mmol/l, participated in the study. The study was performed after a wash-out period of 1 month and a run-in period of 1 month to stabilize patients on a standard diet (CHO 50%, fat 30%, protein 20%, fibre 20 g/day) plus placebo (maltodextrine plus aspartame 15 g/day). At the end of run-in, subjects were randomly assigned to receive sc-FOS (Actilight) (10.6g/day) or placebo (maltodextrine plus aspartame 15 g/day) with tea and/or coffee for a duration of 2 months and thereafter switched to the other treatment for additional 2 months. Plasma glucose, total and lipoprotein (VLDL, LDL, HDL) cholesterol and triglyceride concentrations were measured in the fasting state at the end of run-in and of each treatment period. At the end of the two treatment periods, patients consumed a standard test meal (protein 15%, carbohydrate 34%, fat 51%, kJ 3988) 1h after the administration of 5.3g of sc-FOS or placebo; plasma glucose, insulin, free fatty acid (FFA) and triglyceride responses to the test meal were evaluated.

RESULTS

No significant difference in fasting parameters was detected between the two treatments. After sc-FOS and placebo plasma cholesterol levels were, respectively, 6.47+/-0.70 and 6.44+/-0.78 mmol/l (n.s.) and plasma triglycerides were 1.53+/-0.71 and 1.56+/-0.53 mmol/l (n.s.). No significant differences were observed in cholesterol and triglyceride content of VLDL, LDL and HDL and in plasma Apo A1 levels; conversely, fasting plasma Lp(a) concentrations were significantly increased after sc-FOS (37+/-38 vs. 33+/-35 mg/dl; P<0.005). Postprandial responses of glucose, FFA and triglycerides were not significantly different between sc-FOS and placebo, while postprandial insulin response (incremental area) was significantly reduced after sc-FOS compared to placebo (14,490+/-7416 vs. 17,760+/-7710 pmol/l x 300 min; P<0.02).

CONCLUSIONS

A moderate intake of sc-FOS has no major effects on lipid metabolism, both in the fasting and in the postprandial period, in individuals with mild hypercholesterolaemia. A small but significant increase of Lp(a) concentrations was observed with sc-FOS consumption together with a reduction of the postprandial insulin response; however, the clinical relevance of these small effects is unclear.

A digestive tolerance study of maltitol after occasional and regular consumption in healthy humans

AIM

We aimed to evaluate the gastro-intestinal tolerance to an indigestible bulking sweetener containing sugar alcohol using a double-blind random cross-over study.

METHOD

In order to simulate their usual pattern of consumption, 12 healthy volunteers ingested maltitol or sucrose throughout the day, either occasionally (once a week for each sugar, first period) or regularly (every day for two 9 day periods, second period). In both patterns of consumption, daily sugar doses were increased until diarrhea and/or a grade 3 (ie severe) digestive symptom occurred, at which the dose level was defined as the threshold dose (TD).

RESULTS

In the first period (occasional consumption), the mean TD was 92+/-6 g with maltitol and 106+/-4 g with sucrose (P=0.059). The mean intensity of digestive symptoms was 1.1 and 1.3, respectively (P=NS). Diarrhea appeared in six and one subjects respectively (P=0.035). In the second period (regular consumption), the mean TD was 93+/-9 g with maltitol and 113+/-7 g with sucrose (P=0.008). The mean intensity of digestive symptoms was 1.7 and 1.2, respectively (P=NS). However, diarrhea appeared in eight and three subjects, respectively (P=0.04). Maltitol and sucrose TDs between the two periods were not different.

CONCLUSIONS

Under our experimental conditions, in comparison to sucrose: (a) occasional or regular consumption of maltitol is not associated with severe digestive symptoms; (b) in both patterns of maltitol consumption, diarrhea frequency is higher, but it appeared only for very high doses of maltitol, much greater than those currently used; (c) maltitol does not lead to intestinal flora adaptation after a 9 day period of consumption.

Five-week intake of short-chain fructo-oligosaccharides increases intestinal absorption and status of magnesium in postmenopausal women

Fermentable carbohydrates have been shown to be nondigestible by human enzymes in the small intestine but are fermented extensively in the large bowel to short-chain fatty acids (SCFAs), which can increase mineral absorption. It has been shown that feeding such carbohydrates including short-chain fructo-oligosaccharides (sc-FOSs) increases intestinal magnesium (Mg) absorption in animals, but their beneficial impact on Mg absorption in humans still remains to be established. Therefore, this work aimed to investigate the effect of moderate daily doses of sc-FOSs (10 g/day) on the intestinal absorption and status of Mg in postmenopausal women without hormone replacement therapy (HRT). Eleven healthy postmenopausal women aged 59 +/- 6 years (mean +/- SD) received for 5 weeks sc-FOS or sucrose (placebo) treatments according to a randomized, double-blind, crossover design separated by a washout period of at least 3 weeks. Subjects ingested 87.5 mg of stable isotope 25Mg together with a fecal marker. Subsequently, feces were collected for 5-7 days. An inductively coupled plasma mass spectrometer (ICP/MS) was used for 25Mg stable isotope measurements in feces, urine, and blood. Mg levels were assessed also at the beginning and at the end of each treatment in plasma, erythrocytes, and urine. These measurements allowed for the determination of net intestinal Mg absorption and Mg status. The results show that the addition of 10 g sc-FOS to the diet increased Mg absorption by 12.3%, from 30.2 +/- 5.0% (placebo treatment) to 33.9 +/- 7.2% (sc-FOS treatment; mean +/- SD; p < 0.02). This increase in intestinal Mg absorption was accompanied by an increase in plasma 25Mg level and led to a higher urinary 25Mg excretion. This is the first time that such an effect is shown in humans. The overall conclusion of this work is that the ingestion of moderate doses of sc-FOS did improve intestinal Mg absorption and status in postmenopausal women. Because of the important role of Mg in many cellular functions, such Mg absorption improvement may be particularly interesting when the dietary intake of Mg is limited.

Cytokine mRNA expression in mouse colon: IL-15 mRNA is overexpressed and is highly sensitive to a fibre-like dietary component (short-chain fructo-oligosaccharides) in an Apc gene manner

On the basis of studies using the Min mouse model of colon carcinogenesis, we have recently proposed that a fibre-like food (short-chain fructo-oligosaccharides, sc-FOS) fermented in the colon may stimulate a mechanism of cancer immunosurveillance. In the present paper, we have investigated the expression of cytokines as potential effector molecules. Interleukin (IL-)4, IL-5, IL-13, IL-15 and interferon (INF)-gamma mRNAs were detected by a multi-probe ribonuclease protection assay in C57BL/6J and Min mouse colons. IL-15 mRNA expression was significantly amplified (P=0.01) by the sc-FOS-enriched diet in the colon of Min mice.

Only fibres promoting a stable butyrate producing colonic ecosystem decrease the rate of aberrant crypt foci in rats

BACKGROUND

Dietary fibres have been proposed as protective agents against colon cancer but results of both epidemiological and experimental studies are inconclusive.

AIMS

Hypothesising that protection against colon cancer may be restricted to butyrate producing fibres, we investigated the factors needed for long term stable butyrate production and its relation to susceptibility to colon cancer.

METHODS

A two part randomised blinded study in rats, mimicking a prospective study in humans, was performed using a low fibre control diet (CD) and three high fibre diets: starch free wheat bran (WB), type III resistant starch (RS), and short chain fructo-oligosaccharides (FOS). Using a randomised block design, 96 inbred rats were fed for two, 16, 30, or 44 days to determine the period of adaptation to the diets, fermentation profiles, and effects on the colon, including mucosal proliferation on day 44. Subsequently, 36 rats fed the same diets for 44 days were injected with azoxymethane and checked for aberrant crypt foci 30 days later.

RESULTS

After fermentation had stabilised (44 days), only RS and FOS produced large amounts of butyrate, with a trophic effect in the large intestine. No difference in mucosal proliferation between the diets was noted at this time. In the subsequent experiment one month later, fewer aberrant crypt foci were present in rats fed high butyrate producing diets (RS, p=0.022; FOS, p=0.043).

CONCLUSION

A stable butyrate producing colonic ecosystem related to selected fibres appears to be less conducive to colon carcinogenesis.

Relationships between transit time in man and in vitro fermentation of dietary fiber by fecal bacteria

OBJECTIVE

To assess the effects of drug-induced changes in mean transit time (MTT) on the activity of human fecal flora in vitro.

METHODS

The activity of fecal flora was estimated by the ability of a fecal inoculum to ferment a substrate (beet fiber) in vitro in a batch system for 24 h. The inoculum was collected from 8 healthy volunteers studied during three 3-week randomized periods, who received a controlled diet alone (control period) or the same diet with either cisapride or loperamide. Cisapride and loperamide were adjusted in order to halve and double MTT measured during the control period. At the end of each period, the percentage disappearance of the initial added substrate and the concentration and the profile of short-chain fatty acids (SCFAs), were determined.

RESULTS

In the control period, the pH of the inoculum and SCFA concentration were inversely related to MTT (P=0.0001). Individual SCFA production was also significantly related to MTT (P<0.01). Cisapride-reduced transit time was associated with a significant rise in the concentrations of total SCFAs (P<0.05), propionic and butyric acids (P<0.05) and the percentage substrate disappearance (P<0.05). Inverse relations were observed during the loperamide period. Moreover, MTT was inversely related to the percentage substrate disappearance (P<0.001), SCFA production (P<0.001) and butyrate production (P<0.0005).

CONCLUSION

Changes in MTT alter bacterial activity and modify the bacterial pathways affecting the proportion of individual SCFAs. European Journal of Clinical Nutrition (2000) 54, 603-609

Cholesterol crystallization in gall-bladder bile of pigs given cholesterol-beta-cyclodextrin-enriched diets with either casein or soyabean concentrate as protein sources

Cholesterol precipitation from supersaturated bile is the earliest and determinant step in the formation of cholesterol gallstones, which is thought to be diet-dependent. Bile composition, appearance and growth of cholesterol crystals were studied in fresh gall-bladder biles from pigs adapted to four different protein-containing diets over 3 weeks: 160 g dietary protein/kg as casein (C16; n 6), or as soyabean-protein concentrate (S16; n 6), or a mixture of both protein sources (casein-soyabean protein, 70:30, w/w) (CS16; n 6), or 320 g of the mixed protein/kg (CS32; n 6). Moreover, all four diets contained 3 g cholesterol/kg and 50 g beta-cyclodextrin/kg as modifiers of bile composition towards cholesterol pro-crystallization. Cholesterol precipitation was most active after the high-protein diet, CS32, and the casein diet, C16, and lowest after the soyabean-protein diet, S16. It was intermediate after the mixed diet, CS16, but still much lower than in the former two groups. These diet-induced variations were suggested to be mediated through modifications in the biliary profile of bile acids, whereas all other biliary constituents studied were essentially unchanged. The fasting level of plasma cholesterol was lowest in both 160 g protein/kg diets containing soyabean protein (S16 and CS16), highest for the high-protein diet CS32, and intermediate for the C16 diet. These results should encourage clinical studies on the effect of soyabean protein, or other vegetable proteins, for primary or recurrence prevention of cholelithiasis at its earliest stage.

Olive oil phenolics are dose-dependently absorbed in humans

Olive oil phenolic constituents have been shown, in vitro, to be endowed with potent biological activities including, but not limited to, an antioxidant action. To date, there is no information on the absorption and disposition of such compounds in humans. We report that olive oil phenolics, namely tyrosol and hydroxytyrosol, are dose-dependently absorbed in humans after ingestion and that they are excreted in the urine as glucuronide conjugates. Furthermore, an increase in the dose of phenolics administered increased the proportion of conjugation with glucuronide.

T cell status influences colon tumor occurrence in min mice fed short chain fructo-oligosaccharides as a diet supplement

We have previously shown that addition of short chain fructo-oligosaccharides (indigestible carbohydrates) to food prevented colon tumors in C57BL/6-Apc(Min/+) mice, a model for human colon cancer. As gut-associated lymphoid tissue was concomitantly developed, we suggested that the immune response generated by this food may interfere with carcinogenesis due to involvement of mucosal cells in the regulation of tissue homeostasis. In the present experiment, we tested whether T cell status may influence colon tumor formation in Min mice fed a food supplement of short chain fructo-oligosaccharides. Min mice depleted of CD4(+) and CD8(+) lymphocytes developed twice as many tumors as immunocompetent mice (0.8 as compared with 0.4, the mean number in 7-week-old Min mice when food supplementation began; P = 0.02). It is concluded that food supplementation with a substrate (a known prebiotic) fermented in the colon may stimulate a mechanism of immunosurveillance that would otherwise remain inefficient.

Short-chain fructo-oligosaccharide administration dose-dependently increases fecal bifidobacteria in healthy humans

Short-chain fructo-oligosaccharides (SC-FOS) are a mixture of oligosaccharides consisting of glucose linked to fructose units (Gfn; n = </= 4), which are not digested in the human small intestine but are fermented in the colon where they specifically promote the growth of bifidobacteria. In healthy volunteers, we assessed the tolerance and the threshold dose of SC-FOS that significantly increased fecal bifidobacteria counts and the possibility of a dose-response relationship. Randomly divided into five groups and eating their usual diets, healthy volunteers (40: 18 males, 22 females) ingested in two oral doses for 7 d a powder mixture containing (g SC-FOS/d): 0, G0; 2.5, G2.5; 5, G5; 10, G10; 20, G20. Stools were collected before (d1) and at the end (d8) of sugar consumption, and tolerance was evaluated using a daily chart. Total anaerobe counts were not affected by SC-FOS ingestion. Bifidobacteria counts at d8 were greater in groups G10 and G20 than in G0 and G2.5 (P < 0.05). Fecal pH did not differ among groups. A significant correlation between the dose of SC-FOS ingested and the fecal bifidobacteria counts was observed at d8 (r = 0.53; P < 0.01). Excess flatus was significantly more frequent in subjects consuming G20 than in those consuming G0, G2.5 or G5 (P < 0.05), and more intense in G20 than in G0 and G5 groups (P < 0.05). In conclusion, the optimal and well-tolerated dose of SC-FOS that significantly increased fecal bifidobacteria in healthy volunteers consuming their usual diet is 10 g/d.

Small-intestinal digestion of partially resistant cornstarch in healthy subjects

The aims of this study were to measure the amount of starch from partially resistant starches (retrograded and complexed high-amylose cornstarches) escaping small-intestinal digestion in healthy humans by use of an intubation method and to compare these data with data obtained by indirect in vitro methods. Experiments were carried out in vivo in 6 healthy humans by using ileal intubation and stool analysis and in vitro by using 3 different methods for analyzing resistant starch. In intubated subjects, 51 +/- 2% of the retrograded and 21 +/- 2% of the complexed starch was delivered to the ileum and was fermented almost completely in the colon. In vitro estimates of the absorption of resistant starch were much lower. We conclude that technologically modified starches may substantially increase the amount of carbohydrate available for colonic fermentation in humans, but that in vitro measurements of resistant starch are inaccurate for predicting malabsorption in healthy humans.

Functional food science and substrate metabolism

The present review addresses the role of food constituents in the aetiology of metabolic conditions and chronic diseases, mostly related to energy metabolism and substrate regulation, such as obesity and non-insulin-dependent diabetes mellitus. Second, attention is paid to malnutrition, a major cause of mortality and morbidity in developing countries, which may be a cause of concern in Europe because of the increasing number of elderly people in the population. Finally, the role of diet during exercise, a condition of enormous substrate demands, is evaluated. Based on a critical evaluation of the existing knowledge in the literature, implications for future research in relation to functional foods are discussed.

Plasma lipids and fatty acid synthase activity are regulated by short-chain fructo-oligosaccharides in sucrose-fed insulin-resistant rats

The aim of this study was to evaluate the chronic effects of a short-chain fructo-oligosaccharide (FOS)-containing diet on plasma lipids and the activity of fatty acid synthase (FAS) in insulin-resistant rats. Normal male Sprague-Dawley rats, 5 wk old, were randomly assigned to two groups and fed either a sucrose-rich diet (S, 575 g sucrose /kg diet and 140 g lipids/kg diet) or a sucrose-rich diet supplemented with 10 g/100 g short-chain fructo-oligosaccharides (S/FOS). A third reference group (R) was fed a standard nonpurified diet (g/kg, 575 g starch, 50 g fat). After 3 wk the sucrose-fed rats (compared with the R group) were characterized by the following: 1) higher insulin responses after a glucose challenge (P < 0.05); 2) heavier liver (P < 0.001) and retroperitoneal adipose tissue (P < 0.01); 3) hypertriglyceridemia (P < 0.0001) and higher plasma free fatty acids (P < 0.0001); and 4) higher fatty acid synthase activity in the liver but a low activity in the adipose tissue (P < 0.001). The addition of FOS to the diet resulted in 11% lower liver weight than in the S group (P < 0.05) and tended to result in lower adipose tissue weight (P < 0.11). Plasma triglycerides and plasma free fatty acids were lower in S/FOS- than in S-fed rats (P < 0.05). Chylomicrons + VLDL, and intermediate density lipoprotein (IDL) concentrations did not differ between groups, nor was plasma cholesterol influenced by diet. Hepatic FAS activity was lower in S/FOS-fed rats than in the S-fed rats (P < 0.05). In adipose tissue, however, this activity tended to be greater in rats fed S/FOS than in rats fed the S diet (P < 0.07). In conclusion, in a rat model of diet-induced (57.5% sucrose and 14% lipids) insulin resistance, the addition of short-chain FOS prevented some lipid disorders, lowered fatty acid synthase activity in the liver and tended to raise this activity in the adipose tissue. Short-chain FOS, in addition to being a nondigestible sweetener with good bulking capacity, might be useful in the treatment of insulin resistance and hyperlipidemia.

Plasma leptin and hunger ratings in healthy humans

Leptin, the ob gene product, is considered as a signal involved in the regulation of energy stores through centrally mediated effects on ingestive behavior and metabolism. To investigate the relationships between appetite-related sensations and circulating leptin in humans, 12 healthy male volunteers were served two test lunches (1200 kcal, 38% carbohydrate, 50% fat, 12% protein) with comparable palatability but resulting in different postprandial hunger ratings, and plasma leptin concentrations were monitored during 8 h after meal ingestion. Whereas postprandial hunger ratings (assessed by visual analog scales) and plasma insulin patterns differed significantly between meals, no significant difference in postprandial plasma leptin concentrations was observed between the two meals. A moderate but significant increase in mean plasma leptin was found over time. We conclude that postprandial plasma leptin concentrations do not significantly differ between two meals inducing different effects on hunger subjective feelings. These data are in agreement with a role for leptin in the regulation of energy balance as a long-term adiposity-related signal rather than a short-term meal-related factor.

Metabolic effects of digestible and partially indigestible cornstarch: a study in the absorptive and postabsorptive periods in healthy humans

To compare the effects of digestible (pregelatinized) and partially indigestible (retrograded) cornstarches on some metabolic indexes, we studied eight healthy volunteers during two periods separated by 1 wk. In each period, fasting volunteers consumed at 0800 the test meal containing either the digestible or partially indigestible cornstarch; blood and breath were sampled in the absorptive period for 8 h. To study its late effects, the same test meal as that served at 0800 was given again at 2200, and blood and breath were sampled for 3 h in the postabsorptive period the next morning, i.e., 10 h after ingestion of the test meal. In the absorptive period, blood glucose and insulin were significantly higher after ingestion of digestible cornstarch than after partially indigestible cornstarch. In the postabsorptive period concentrations of blood glucose, insulin, and fatty acids were not significantly different, whereas concentrations of blood acetate, breath hydrogen, methane, and 13CO2, and the respiratory quotient and satiety were significantly higher (P < 0.05) and concentrations of blood glycerol significantly lower (P < 0.05) after ingestion of partially indigestible cornstarch than after digestible cornstarch. We conclude that in healthy humans, digestion of partially indigestible cornstarch is slow in the small intestine and its colonic fermentation continues 10-13 h after its ingestion. Compared with pregelatinized cornstarch, the shift in starch digestion induced by retrogradation leads to a reduction in glycemic and insulinemic responses in the absorptive period and in lipolysis in the postabsorptive.

Whole-body protein turnover in humans fed a soy protein-rich vegetable diet

OBJECTIVES

This study was designed to compare the whole-body protein turnover in humans after the ingestion of a soy protein-rich vegetable diet with that of a control group fed a western animal protein-rich diet.

SUBJECTS

Twelve male volunteers were divided into two groups of six subjects who were given for two weeks either a 85% vegetable protein diet (diet VP) or a control western animal protein-rich diet (diet AP).

INTERVENTIONS

Whole-body protein turnover was estimated at the end of the two-week controlled diet period using the [15N]-glycine end-product method. Nitrogen flux rates were determined in the fed state (1.3 g protein/kg) over a 9 h period after the dose of [15N]-glycine was given.

RESULTS

After the 9 h of the test, the urinary ammonia excretion was significantly higher in the group receiving the diet AP than that in the group receiving the diet VP (P < 0.05). In contrast, there was no significant difference for both total nitrogen and urea nitrogen excretions. Both the protein synthesis and the protein breakdown were similar in both groups. In the same way, the net protein deposition measured in the fed state during 9 h was similar for both diets at 0.07 g/kg/h.

CONCLUSIONS

Young adults fed 1.3 g/kg/d of either meat or vegetable protein-rich diet for two weeks did not show a different protein turnover.

How the degree of unsaturation of dietary fatty acids influences the glucose and insulin responses to different carbohydrates in mixed meals

The association of fats with carbohydrates results in a lower glucose response but the influence of the nature of the dietary fatty acids has not been investigated clearly. We examined the effect of the degree of dietary fatty acid unsaturation on the postprandial glucose and insulin responses to a mixed meal. Eight young normolipidemic men consumed four different meals in random order. The meals differed in the nature of their oils and in the type of their main carbohydrates. The meals contained either a high ratio of monounsaturated to polyunsaturated n-6 fatty acids (MUFA) or a low ratio (PUFA) and either potatoes or parboiled rice. Proteins and saturated and polyunsaturated n-3 fatty acid contents were not different among meals. Blood samples were collected every 30 min for 3 h after the test meal. The glucose response was significantly lower 30 min after the parboiled rice-PUFA meal than after parboiled rice-MUFA or potato-MUFA (P < 0.05) meals. The insulin response was lower after parboiled rice-PUFA than after potato-MUFA (P < 0.05) meals. Similarly, an effect of fat appeared after 30 min. Glucose responses (F = 1.4, P < 0.01) and insulin responses (F = 5.3, P < 0.05) to both carbohydrates were significantly lower with dietary PUFA compared with dietary MUFA. In conclusion, the degree of dietary fatty acid unsaturation (18:1 compared with 18:2) may influence the glucose and insulin responses to mixed meals.

Short-chain fructo-oligosaccharides reduce the occurrence of colon tumors and develop gut-associated lymphoid tissue in Min mice

C57BL/6J-Min/+ mice, which are heterozygous for a non-sense mutation in the Apc gene, provide a model for both familial adenomatous polyposis and sporadic colon cancers. In our study, gut tumors and small intestine lymphoid nodules were counted in Min mice fed fiber-enriched diets for 6 weeks. Neither starch-free wheat bran nor resistant starch modified the number of tumors. However, short-chain fructo-oligosaccharides dramatically reduced the incidence of colon tumors and concomitantly developed gut-associated lymphoid tissue. Our experiment shows that short-chain fructo-oligosaccharides counteract advanced stages of colon carcinogenesis, possibly via stimulation of antitumoral immunity by modulation of the colonic ecosystem.

Effects of resistant starch- and vitamin A-supplemented diets on the promotion of precursor lesions of colon cancer in rats

We have evaluated the potential protective effect of resistant starch (RS)- and vitamin A-supplemented diets on the promotion of preneoplasic lesions of rat colon, aberrant crypt foci (ACF), induced by 1,2-dimethylhydrazine dihydrochloride (DMH). We have tried to show whether the association of these two dietary constituents in the same diet could have synergistic effects. RS, vitamin A, and RS+ vitamin A were incorporated into the rat diets. Experimental diets were given one week after DMH injection and maintained for 12 weeks until the animals were sacrificed. The total number of ACF decreased with the three experimental diets. For RS- and RS + vitamin A-supplemented diets, this decrease is primarily due to a decrease in small ACF. For the vitamin A-supplemented diet, small and large ACF have a tendency to decrease. The effects of the diets on parameters influencing colon carcinogenesis were also studied. Only RS- and RS + vitamin A-supplemented diets have modified cecal pH, fecal and cecal butyrate contents, fecal excretion, cecal weight, and colon length. Vitamin A has been observed in colonic epithelial cells of rats receiving vitamin A- and RS+ vitamin A-supplemented diets. The association between RS and vitamin A shows neither a cumulative nor a synergistic protective effect.

Digestion, excretion, and energy value of fructooligosaccharides in healthy humans

The fate of fructooligosaccharides (FOS) in the human gastrointestinal tract was evaluated in six healthy volunteers over an 11-d period. After an equilibration phase, 20.1 g FOS/d was given in three identical postprandial doses. Distal ileal output of FOS and their constituent components were determined by intestinal aspiration after a single meal, and the amounts of FOS excreted in stools and urine were also measured. Most of ingested FOS, 89 +/- 8.3% (mean +/- SEM), was not absorbed in the small intestine, and none was excreted in stools, indicating that the portion reaching the colon was completely fermented by colonic flora. A small fraction of ingested FOS was recovered in urine. The mean estimated energy value of FOS was 9.5 kJ/g. We conclude that in healthy humans, FOS are only slightly digested in the small intestine and then fermented in the colon, resulting in reduced energy production.

Relations between transit time, fermentation products, and hydrogen consuming flora in healthy humans

BACKGROUND/AIMS

To investigate whether transit time could influence H2 consuming flora and certain indices of colonic bacterial fermentation.

METHODS

Eight healthy volunteers (four methane excretors and four non-methane excretors) were studied for three, three week periods during which they received a controlled diet alone (control period), and then the same diet with cisapride or loperamide. At the end of each period, mean transit time (MTT) was estimated, an H2 lactulose breath test was performed, and stools were analysed.

RESULTS

In the control period, transit time was inversely related to faecal weight, sulphate reducing bacteria counts, concentrations of total short chain fatty acids (SCFAs), propionic and butyric acids, and H2 excreted in breath after lactulose ingestion. Conversely, transit time was positively related to faecal pH and tended to be related to methanogen counts. Methanogenic bacteria counts were inversely related to those of sulphate reducing bacteria and methane excretors had slower MTT and lower sulphate reducing bacteria counts than non-methane excretors. Compared with the control period, MTT was significantly shortened (p < 0.05) by cisapride and prolonged (p < 0.05) by loperamide (73 (11) hours, 47 (5) hours and 147 (12) hours for control, cisapride, and loperamide, respectively, mean (SD)). Cisapride reduced transit time was associated with (a) a significant rise in faecal weight, sulphate reducing bacteria, concentrations of total SCFAs, and propionic and butyric acids and breath H2 as well as (b) a significant fall in faecal pH and breath CH4 excretion, and (c) a non-significant decrease in the counts of methanogenic bacteria. Reverse relations were roughly the same during the loperamide period including a significant rise in the counts of methanogenic bacteria and a significant fall in those of sulphate reducing bacteria.

CONCLUSIONS

Transit time differences between healthy volunteers are associated with differences in H2 consuming flora and certain indices of colonic fermentation. Considering the effects of some fermentation products on intestinal morphology and function, these variations may be relevant to the pathogenesis of colorectal diseases.

Effects of long-term low-glycaemic index starchy food on plasma glucose and lipid concentrations and adipose tissue cellularity in normal and diabetic rats

The present study aimed to assess the metabolic consequences of the chronic ingestion of two starches giving different postprandial glycaemic responses in normal and diabetic rats. The two starches chosen were mung-bean (Phaseolus aureus) starch (97% pure starch) and wheat starch presented as ground French toast. First, we studied the characteristics of these two starches. In vitro the alpha-amylase (EC 3.2.1.1) digestibilities of these starches were 40 (SE 3) and 62 (SE 4)% respectively at 30 min, whereas the contents of resistant starch were 77 (SE 4) and 22 (SE 4) g/kg respectively. In vivo the mung-bean starch produced lower postprandial glycaemic responses than the wheat starch (areas under the curve were: 91 (SE 28) and 208 (SE 33) mmol.min/l, P < 0.05) in normal rats (n 8). We then submitted twenty-eight normal and twenty-eight diabetic (neonatal streptozotocin on second day of birth) male Sprague-Dawley rats (6 weeks old) to a diet containing 570 g starch/kg as either mung-bean starch or wheat starch (n 14 rats/group). After 5 weeks on the diets food intakes and body weights were identical in each group. Liver and kidney weights were comparable when expressed as relative weight. The mung-bean-starch diet slightly decreased epididymal fat-pad weight (P < 0.14, ANOVA) and led to a marked decrease in adipocyte volume (P < 0.05). Plasma triacylglycerol and phospholipid concentrations were lower after the mung-bean-starch diet than after the wheat-starch diet in both normal and diabetic rats, whereas free fatty acid concentrations were lower only in normal rats. Similarly, non-fasting plasma glucose concentrations decreased (P < 0.05) in normal rats fed on mung-bean starch but not in diabetic ones (P < 0.14). Insulin levels tended to be lower, but not significantly, after mung-bean-starch feeding than after wheat starch. We conclude that the replacement of 570 g wheat starch/kg diet with mung-bean starch for 5 weeks resulted in (1) lowered non-fasting plasma glucose and free fatty acid levels in normal but not in diabetic rats, (2) a reduction in plasma triacylglycerol concentration and adipocyte volume in both normal and diabetic rats. Thus, the type of starch mixed into the diet may have important metabolic consequences in normal and diabetic rats.

Effects of fructo-oligosaccharides ingestion on fecal bifidobacteria and selected metabolic indexes of colon carcinogenesis in healthy humans

Fructo-oligosaccharides (FOS) are a mixture of oligosaccharides consisting of glucose linked to fructose units. They are not digested in the human small intestine but fermented in the colon, where they could specifically promote the growth of some species of the indigenous microflora, especially bifidobacteria. We assessed in healthy humans the effects of FOS ingestion in fecal bifidobacteria and selected metabolic indexes potentially involved in colonic carcinogenesis. Twenty volunteers randomly divided into two groups were studied for three consecutive 12-day periods. During the ingestion period, they received 12.5 g/day FOS or placebo (saccharose) in three oral doses. Stools were regularly collected and analyzed. FOS ingestion led to an increase in fecal bifidobacterial counts [7.9 +/- 0.5 to 9.1 +/- 0.3 (SE) log colony-forming units/g wet wt, p < 0.01] and beta-fructosidase activity (9.6 +/- 1.9 to 13.8 +/- 1.9 IU/g dry wt, p < 0.01). In contrast, FOS ingestion had no significant effect on fecal total anaerobes, pH, the activities of nitroreductase, azoreductase, and beta-glucuronidase, and the concentrations of bile acids and neutral sterols. We conclude that ingestion of FOS, at a clinically tolerated dose of 12.5 g/day, led to an increase in colonic bifidobacteria. This effect was not associated in healthy humans with beneficial changes in various factors potentially involved in the pathogenesis of colonic cancer.

Symptomatic response to varying levels of fructo-oligosaccharides consumed occasionally or regularly

OBJECTIVE

To evaluate in 14 healthy volunteers the gastrointestinal tolerance to an indigestible bulking sweetener containing fructo-oligosaccharides (FOS).

DESIGN

In order to mimic their usual pattern of consumption, FOS were ingested throughout the day either occasionally (once a week, first period) or regularly (every day, second period). In the two patterns of consumption, daily sugar doses were increased until diarrhoea and/or a symptom graded 3 (i.e. severe) occurred, or when subjects did not want to ingest more candies.

SETTING

Clinical Nutrition Unit, Hôpital Saint-Lazare, Paris.

RESULTS

In both periods, the first symptom which occurred was excessive flatus (> 30 g FOS/day): borborygmi and bloating appeared at a higher level (> 40 g/day); lastly, abdominal cramps and diarrhoea occurred at a very much higher level (50 g/day). The volumes of hydrogen excreted in breath in response to the same load of FOS were not different between the two periods.

CONCLUSIONS

Chronic consumption of FOS initiated cautiously with subsequent gradual increase did not improve tolerance, nor reduce breath excretion of hydrogen.

Colonic microflora: nutrition and health. Summary and conclusions of an International Life Sciences Institute (ILSI) [Europe] workshop held in Barcelona, Spain

The colonic microflora is an organism that performs a variety of unique activities. It is more important to evaluate these activities than to analyze bacterial composition in terms of genera, species, or strains. Unless the bacteria translocate, it is the activities of the colonic microflora that affect colonic and systemic physiology and not the bacteria themselves.

An interleukin 2/sodium butyrate combination as immunotherapy for rat colon cancer peritoneal carcinomatosis

BACKGROUND/AIMS

Immunotherapy using interleukin 2 has had disappointing results in the treatment of colon cancer. Overcoming escape mechanisms, such as lack of antigen presentation and absence of accessory adhesion molecules on cancer cells, may increase its efficiency. We tried to do so by modifying the phenotype of the weakly immunogenic rat colon cancer PROb cells with sodium butyrate.

METHODS

After in vitro treatment with butyrate, PROb cells were tested for lymphokine-activated killer cell sensitivity and, using cytofluorometry, expression of adhesion molecules. We then treated established PROb peritoneal carcinomatoses with intraperitoneal injections of interleukin 2 and butyrate. Tumors were studied histologically and immunohistochemically. We tested the specificity of the immune protection by subsequent subcutaneous challenges with either PROb or glioma cells and by Winn's assay.

RESULTS

Butyrate increased lymphokine-activated killer cell sensitivity and expression of major histocompatibility complex class I and intercellular adhesion molecule 1 in vitro. Interleukin 2/butyrate combination resulted in cases of complete cure of carcinomatosis with specific protection against PROb cells. We noticed a complex stroma reaction with numerous functional antigen presenting cells close to PROb cells.

CONCLUSIONS

The complete regression of tumor masses may be attributed, at least in part, to a butyrate-induced increase in immunogenicity of the cancer cells. This new combined immunotherapy may be of interest in the treatment of colon cancer.

Glycaemic and insulinaemic responses in healthy volunteers upon ingestion of maltitol and hydrogenated glucose syrups

Glycaemic and insulinaemic index of maltitol and maltitol-containing chocolate have been determined in healthy subjects with reference to glucose and compared with those of sucrose solution and sucrose containing chocolate. All maltitol containing products (solutions and chocolate) show a reduced glycaemic index. Insulinaemic index of maltitol solutions is also low, while that of maltitol chocolate remains high.

Role of viscous guar gums in lowering the glycemic response after a solid meal

The aim of the present study was to investigate how guar gum viscosity acts on starch digestion and glucose absorption in humans. Six healthy subjects received a mixed diet composed of 60.4% carbohydrate in the form of maize glucose or pregelatinized starch, to which was added 5.6% low- or high-viscosity guar gums. Meals were ingested or instilled in the duodenum and postprandial insulin and glucose responses were monitored for 3 h. Infusion of meals containing glucose showed that the delay in the diffusion rate to the duodenal mucosa due to bolus viscosity was not significant. Infusion of meals containing starch showed that a decrease in the digestion rate of starch in the upper small intestine accounted for part of the effect of viscosity on glycemic response, whereas the main effect of guar gum was apparently to slow gastric emptying.

[Treatment with butyrate/IL-2 combination in peritoneal carcinomatosis of colonic origin]

Two therapeutic assays associating sodium butyrate (NaB) and interleukin-2 (IL-2) were applied on rats after intraperitoneal (i.p.) injection of colon carcinoma cells. The first assay began at day 1 after cell injection, and the second one at day 10 after injection, i.e. when carcinomatosis was established. IL-2 was given i.p. three times per day and NaB one time per day, for five and seven days respectively. The survival median of IL-2 treated rats significantly increased versus those of untreated ones, and was much higher with NaB in supplement. Moreover, using this associative treatment, we observed some cases of complete curacy, even in rats bearing established carcinomatosis.

Breath hydrogen response to lactulose in healthy subjects: relationship to methane producing status

In order to assess the relationship between methane (CH4) producing status and the breath excretion of hydrogen (H2) in healthy subjects, breath CH4 and H2 were simultaneously measured for 14 hours after oral ingestion of 10 g lactulose in 65 young volunteers. Forty were breath CH4 producers and 25 were not. Statistically significant differences were observed between both groups, with lower values for CH4 producers recorded for the following parameters: fasting basal value of breath H2 (8.1 (4.9) v 5.2 (3.7) ppm, p less than 0.05), mouth-to-caecum transit time (68 (24) v 111 (52) min, p less than 0.005), and breath H2 production measured as area under the curve 13.1 (6.9) v 8.8 (3.8) 10(3) ppm/min, p less than 0.02). There was no significant correlation between individual production of breath H2 and CH4. These results indicate that the response to lactulose depends on breath CH4 producing status. In clinical practice, defining normal values of mouth-to-caecum transit time without knowledge of breath CH4 producing status may lead to misinterpretation of the H2 breath test.

Lack of detectable deleterious effects on metabolic control of daily fructose ingestion for 2 mo in NIDDM patients

The effects of a daily intake of 30 g fructose on blood glucose regulation, erythrocyte insulin receptors, and lipid metabolism have been studied in type II (non-insulin-dependent) diabetic subjects. Eight well-controlled patients received, in a randomly assigned crossover design over two 2-mo study periods, 30 g of fructose in exchange for an isocaloric amount of starch. Fructose could be taken at any time during the day as part of the 1400-1600 kcal allowed diet (50% carbohydrate, 30% fat, 20% protein). No significant difference was observed concerning body weight, HbA1c, fasting plasma glucose, fasting plasma insulin, uric acid, total cholesterol, high-density lipoprotein cholesterol, and triglycerides, nor was there any change in insulin binding to erythrocytes between the fructose and the control starch period. However, the mean plasma triglyceride levels after the fructose period, although still in the normal range, were significantly higher than baseline values (P less than .05). We conclude that moderate amounts of fructose incorporated into the diet of well-controlled type II diabetic subjects have no significant deleterious effect on glycemic control, insulin receptors of erythrocytes, or lipid metabolism.

In vitro and in vivo digestibility and metabolic effects of 3 wheat-flour products (white bread, french toast (rusk) and french toast bran-enriched) in normal subjects

We devised to study the effects of two technological processings of industrial bread (degree of cooking and enrichment with bran) on in vitro digestibility and repercussions on carbohydrate metabolism in healthy subjects. 3 products were tested in vitro and in vivo: white bread (WB), french toast obtained from the same white bread (FT) and french toast enriched with bran (BFT). In vitro, the percentage of starch hydrolysed was significantly lower for the bran-enriched toast than for WB and FT (p less than 0.001). In vivo, the 3 products and an oral glucose load were given at 08.00 h, after an overnight fast, to 12 healthy volunteers (8 F; 4 M); (age = 24 +/- 1 years; BMI = 21.9 +/- 0.9; mean +/- SEM) on four consecutive days and in random order (latin squares 3 x 4). Each meal contained 35 g carbohydrate and 125 ml water and, for the wheat products, about 190 Kcal. The mean results of the glycemic indexes were: WB = 115 +/- 17%; FT = 99 +/- 21%; BFT = 87 +/- 21% (NS) with the corresponding insulin indexes at 81 +/- 8%, 79 +/- 9% and 90 +/- 8% respectively (NS). The mean plasma glucose and insulin values at 30 minutes did not differ between the three tested foods but were all significantly lower than that observed with glucose (p less than 0.01). Plasma glucose transiently descended below baseline values in all subjects for glucose and BFT. Neither the toasting process nor the presence of wheat bran had any major effect upon hyperglycemia and insulin secretion in the healthy subjects studied.

Sucrose or honey at breakfast have no additional acute hyperglycaemic effect over an isoglucidic amount of bread in type 2 diabetic patients

Exclusion of simple sugars from the diabetic diet is not always followed by patients and may not even be as crucial as was hitherto thought. We tested three types of mixed breakfasts (400 kcal, 50 g HCO) including an isoglucidic amount either of white bread (30 g), honey (20 g) or sucrose (15 g), at the critical morning period i.e. for breakfast, in a group of 21 Type 2 (non-insulin-dependent) diabetic patients (6 well- and 15 badly controlled). Mean plasma glucose and insulin levels were comparable on the three occasions: respectively with bread, sucrose and honey, peak glucose values were 18 mmol/l, 17.7 mmol/l and 17.5 mmol/l in the uncontrolled group versus 13.9 mmol/l, 12.8 mmol/l and 12.7 mmol/l in the well-controlled group. Peak insulin values were 33.6 mU/1,34.0 mU/l and 36.3 mU/l (p greater than 0.05) in uncontrolled patients against 57.5 mU/l, 54.8 mU/l and 52.5 mU/l in well-controlled subjects (p greater than 0.05). The mean increment in peak plasma glucose values for the three breakfasts was as follows: 6.9 mmol/l, 6.3 mmol/l and 6.2 mmol/l for the uncontrolled group against 7.2 mmol/l, 5.9 mmol/l and 6.2 mmol/l in well-controlled subjects; the mean increment in peak plasma insulin levels was 21.8 mU/l,22.0 mU/l and 24.2 mU/l in the controlled group versus 38.2 mU/l, 32.0 mU/l and 34.7 mU/l in the well-controlled subjects, all values being non-significantly different (p greater than 0.05). We conclude that, in acute conditions, simple sugars have no additional hyperglycaemic effect over an isoglucidic amount of bread in well-and in badly controlled Type 2 diabetic patients, even at breakfast.

Sucrose taken during mixed meal has no additional hyperglycaemic action over isocaloric amounts of starch in well-controlled diabetics

The hyperglycaemic effect of 20 g sucrose taken at the end of a regular mixed meal by diabetic patients was measured in six adult type 1 diabetics, C-peptide negative, controlled by the artificial pancreas, and twelve adult type 2 diabetics, with fasting plasma glucose levels below 7.2 mmol/l (130 mg/100 ml) and post-prandial plasma glucose levels below 10.0 mmol/l (180 mg/100 ml), treated by diet alone or with glibenclamide and/or metformin. All the patients were given on consecutive days, in random order, two mixed meals of grilled meat, green beans, and cheese, as well as a cake made either of rice, skimmed milk, and saccharine (meal A) or rice, skimmed milk, and 20 g sucrose (meal B). The meals contained equal amounts of calories and of carbohydrate. There was no difference between the meals in plasma glucose curves and plasma insulin or insulin infusion rate variations whether in peak values, peaking times, or areas under the curves, in either group of patients. Sparing use of sucrose taken during mixed meals might help well-controlled diabetic patients to comply with their daily dietary prescription while maintaining good blood glucose control.