We have recently reported that soluble dietary fibre, glucomannan, increased colonic alkaline phosphatase (ALP) activity and the gene expression without affecting the small-intestinal activity and that colonic ALP was correlated with gut mucins (index of intestinal barrier function). We speculated that dietary fermentable carbohydrates including oligosaccharides commonly elevate colonic ALP and gene expression as well as increase mucin secretion and microbial fermentation. To test this hypothesis, male Sprague–Dawley rats were fed a diet containing 30 % lard with or without 4 % fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose (RAF) and lactulose (LAC), which are non-digestible oligosaccharides or isomalto-oligosaccharides (IMOS; some digestible oligosaccharides) for 2 weeks. Colon ALP activity, the gene expression and gut luminal variables including mucins, organic acids and microbiota were measured. Colonic ALP was significantly elevated in the FOS, RAF and LAC groups, and a similar trend was observed in the GOS group. Colonic expression of intestinal alkaline phosphatase (IAP-I), an ALP gene, was significantly elevated in the FOS, GOS and RAF groups and tended to be increased in the LAC group. Dietary FOS, GOS, RAF and LAC significantly elevated faecal mucins, caecal n-butyrate and faecal ratio of Bifidobacterium spp. Dietary IMOS had no effect on colonic ALP, mucins, organic acids and microbiota. Colon ALP was correlated with mucins, caecal n-butyrate and faecal Bifidobacterium spp. This study demonstrated that non-digestible and fermentable oligosaccharides commonly elevate colonic ALP activity and the expression of IAP-I, with increasing mucins and microbial fermentation, which might be important for protection of gut epithelial homoeostasis.

Increased intestinal permeability (IP) can lead to compromised health. Limited in vivo IP research has been conducted in chickens. The objectives of the current study were to develop a model of increased IP utilizing lipopolysaccharide (LPS Escherichia coli O55:B5) and to evaluate IP changes using the lactulose, mannitol and rhamnose (LMR) sugar permeability test. In addition, fluorescein isothiocyanate dextran (FITC-d), d-lactate, zonula occludens (ZO-1) and diamine oxidase (DAO) permeability tests were employed. Male Ross chickens were reared until day 14 on the floor in an animal care facility and then transferred to individual cages in three separate experiments. In each of experiments 1 and 2, 36 chicks were randomly allocated to receive either saline (control) or LPS (n=18/group). Lactulose, mannitol and rhamnose sugar concentration in blood was measured at 0, 30, 60, 90, 120 and 180 min in experiment 1, at 60, 90 and 120 min in experiment 2 and at 90 min in experiment 3 (n=16/group). Lipopolysaccharide was injected intraperitoneally at doses of 0.5, 1 and 1 mg/kg BW in experiments 1, 2 and 3, respectively, on days 16, 18 and 20, whereas control received sterile saline. On day 21, only birds in experiments 1 and 2 were fasted for 19.5 h. Chicks were orally gavaged with the LMR sugars (0.25 gL, 0.05 gM, 0.05 gR/bird) followed by blood collection (from the brachial vein) as per time point for each experiment. Only in experiment 3, were birds given an additional oral gavage of FITC-d (2.2 mg/ml per bird) 60 min after the first gavage. Plasma d-lactate, ZO-1 and DAO concentrations were also determined by ELISA in experiment 3 (n=10). Administration of LPS did not affect IP as measured by the LMR sugar test compared with control. This was also confirmed by FITC-d and DAO levels in experiment 3 (P>0.05). The plasma levels of d-lactate were decreased (P<0.05). Plasma levels of ZO-1 were increased in the third experiment only and did not change in the first two experiments. Lipopolysaccharide at doses of 0.5 and 1 mg/kg did not increase IP in this model system. In conclusion, the LMR sugar can be detected in blood 90 min after the oral gavage. Further studies are needed for the applicability of LMR sugars tests.

It is important to provide formula-fed infants with a bifidobacteria-enriched gut microbiota similar to those of breastfed infants to ensure intestinal health. Prebiotics, such as certain oligosaccharides, are a useful solution to this problem, but the combinational benefits of these oligosaccharides have not been evaluated. This study investigated the benefits of oligosaccharide combinations and screened for an optimal combination of oligosaccharides to promote healthy gut microbiota of formula-fed infants. In vitro and in vivo experiments were performed to assess the bifidogenic effects of lactulose (LAC) alone and LAC combined with raffinose (RAF) and/or galacto-oligosaccharide (GOS), using a mixed culture model and neonatal mice orally administered with these oligosaccharides and Bifidobacterium breve. In the in vitro culture model, the combination of the three oligosaccharides (LAC–RAF–GOS) significantly increased cell numbers of B. breve and Bifidobacterium longum (P<0·05) compared with either LAC alone or the combination of two oligosaccharides, and resulted in the production of SCFA under anaerobic conditions. In the in vivo experiment, the LAC–RAF–GOS combination significantly increased cell numbers of B. breve and Bacteroidetes in the large intestinal content (P<0·05) and increased acetate concentrations in the caecal content and serum of neonatal mice. Genes related to metabolism and immune responses were differentially expressed in the liver and large intestine of mice administered with LAC–RAF–GOS. These results indicate a synergistic effect of the LAC–RAF–GOS combination on the growth of bifidobacteria and reveal possible benefits of this combination to the gut microbiota and health of infants.

Prebiotics are suggested as an alternative to antibiotics in animal rearing. Fermentable substances such as inulin or lactulose have been proposed to stimulate the immune system and health by modulation of the intestinal flora and its fermentation products. In this study, effects of inulin and lactulose on the intestinal health and hematology of calves have been investigated. Both prebiotics significantly decreased thrombocyte counts in peripheral blood. Only inulin was able to increase hemoglobin concentration and hematocrit. Total leukocyte count was decreased by lactulose while both prebiotics tended to lower monocyte proportions. mRNA expression of inflammation-related markers in the intestine was also affected by both prebiotics hinting at a decreased inflammatory status. This may be due to a possible decrease in intestinal pathogen load that remains to be verified. Only mRNA amounts of interleukin 8 were increased by lactulose in mesenteric lymph nodes. In the ileum, expression of a proliferation marker was increased by inulin while an apoptosis-related gene was increased by both prebiotics. The results of this study show a clear effect of prebiotics on certain parameters associated with animal health and performance that remain to be studied in detail in future investigations.

The H2 breath test is ideal for orocaecal transit time (OCTT) measurement, as it is non-invasive and inexpensive. Indigestible substrates added to a test meal are metabolised by the colonic bacteria, resulting in the production of H2 which is detected in end-exhalation breath. However, the substrates themselves can alter the transit times in the gastrointestinal tract. The aim of the present study is to compare OCTT and gastric emptying (GE) when lactulose in liquid (L-L), solid lactulose (L-S) and solid inulin (IN-S) are added to a test meal, and subsequently, to examine if inulin alters GE. Firstly, ten male volunteers were tested on three occasions. Volunteers ate a pancake breakfast containing 100 mg of 13C-octanoic acid and either 12 g of L-L, 12 g of L-S or 12 g of IN-S in a randomised order. Secondly, seven male volunteers were tested twice with meals containing either 12 g of IN-S or no substrate (NO-S). L-L induced the shortest OCTT (85·3 (sd 42·8) min) compared with L-S (162·4 (sd 62·6) min) and inulin (292·4 (sd 66·7) min; P = 0·007). GE half-time and lag phase (L-L: 61 (sd 9); L-S: 57 (sd 10); IN-S: 52 (sd 10) min; P = 0·005) were also affected, with L-L being the slowest. Thirdly, inulin reduced GE lag and latency phases (P < 0·05) compared with NO-S. Lactulose accelerates OCTT but delays GE compared with inulin. Inulin accelerates the onset of stomach emptying, but it has no effect on GE half-time. For these reasons, inulin is the preferred substrate for the H2 breath test.

For some time now prebiotics have been proposed to improve health by stimulation of beneficial bacteria in the intestine of humans and animals. The current study is aiming to show effects of feeding of either 2% inulin or 2% lactulose in milk replacer on performance and intestinal morphology of male Holstein–Friesian calves. After 20 weeks of feeding inulin led to significantly higher daily weight gains than lactulose while control animals ranged between the experimental feedings. Ingestion of milk replacer was reduced in lactulose treated animals. Additionally differences of villus height in jejunum (P = 0.07) and ileum (P = 0.03) could be found with an increase for lactulose treated animals and a decrease for inulin treated animals. In ileum the density of proliferative epithelial cells tended to be lower in inulin treated and higher in lactulose treated animals (P = 0.08). Both inulin and lactulose tended to decrease the quantity of goblet cells in the tips of ileal villi (P = 0.07). Both prebiotics can affect performance and intestinal morphology of calves and may as such affect animal health. But effects differ between substances.

Bifidogenic effect and stimulation of short chain fatty acid (SCFA) production by fractions of oligosaccharides with a DP⩾3 and Gal β(1-6) linkages synthesised from lactose or lactulose by Pectinex Ultra SP-L and Lactozym 3000 L HP G were evaluated in human faecal slurries. Results were compared with those obtained for the commercial oligosaccharide mixture Vivinal®-GOS. Quantitative real-time PCR showed that all galacto-oligosaccharide (GOS) fractions stimulated slightly higher bifidobacteria growth than lactose, lactulose and Vivinal®-GOS. GOS fractions promoted the production of total SCFA and acetic acid in a similar way to Vivinal®-GOS and more than glucose, lactose and lactulose. In conclusion, oligosaccharides derived from lactose and lactulose may represent a suitable alternative to lactulose for the design of new functional food ingredients.

In genetically susceptible individuals, an altered mucosal immune response against some commensal bacteria of the gut ecosystem appears to be the principal mechanism leading to intestinal lesions in inflammatory bowel disease (IBD). The information currently available does not provide an exact explanation about the origin of this important dysfunction of the interaction between host and commensal bacteria, but an altered microbial composition has been detected in the gut ecosystem of patients with Crohn's disease or ulcerative colitis. Prebiotics are food ingredients not digested nor absorbed in the upper intestinal tract that are fermented by intestinal bacteria in a selective way promoting changes in the gut ecosystem. Experimental and human studies have shown that inulin and oligofructose stimulate saccharolysis in the colonic lumen and favour the growth of indigenous lactobacilli and bifidobacteria. These effects are associated with reduced mucosal inflammation in animal models of IBD. Strong experimental evidence supports the hypothesis that inulin and oligofructose can offer an opportunity to prevent or mitigate intestinal inflammatory lesions in human Crohn's disease, ulcerative colitis, and pouchitis. Encouraging results have been obtained in preliminary clinical trials.

The synthetic disaccharide lactulose is known to improve the intestinal microflora by stimulating the growth of selected probiotic bacteria in the gut. In our experiment the effects of lactulose in combination with the probiotic bacteria Enterococcus faecium on growth performance and morphology of the bovine intestine were examined. Calves aged 39 ± 2 days were randomised to three feeding groups (no. = 14 each group): control (L0), fed milk replacer (MR) containing E. faecium; a lactulose group (L1) containing additional 1% lactulose and a second lactulose group (L3) containing 3% lactulose dry matter. The calves were weighed weekly. After 19 weeks the calves were slaughtered and tissues were collected for histological studies. The average daily live weight gain tended to be higher (P < 0.1) for L3 (1350 g/day) than L0 (1288 g/day). Compared with L0, a reduction (P < 0.001) of ileal villus height due to lactulose treatment of approximately 14% in group L1 and 20% in L3 was determined. A significant decrease in the depth of the crypts about 12% in L1 and 8% in L3 was detected in the caecum. The surface area of lymph follicles from Peyer's patches was decreased by lactulose treatment. Results show that lactulose has an effect on the morphology of intestine. A significant effect on growth performance can not be confirmed. However, results permit the conclusion that lactulose feeding has the tendency to increase growth performance.

The contents of short-chain fatty acids were investigated in rats fed lactitol, lactulose and four fructo-oligosaccharides of different degree of polymerisation and solubility. Fructo-oligosaccharides with a low degree of polymerisation (2–8) generated the highest levels of butyric acid all along the hindgut, whereas fructo-oligosaccharides with a high degree of polymerisation (10–60) generated the highest levels of propionic acid. These specific differences were also generally reflected in the caecal pools and molar proportions of short-chain fatty acids. The lower solubility of the fructo-oligosaccharides was related to a lower degree of caecal fermentation. Lactulose and lactitol yielded high proportions of acetic acid and low proportions of butyric acid. It is concluded that both the degree of polymerisation and the solubility may affect short-chain fatty acid formation, whereas the fructose content per se seem to be of less importance. This may be of interest when designing foods with specific health effects.

Erythritol, a naturally occurring polyol, is gaining attention as a bulk sweetener for human nutrition. Industrially, it is produced from glucose by fermentation. From various studies it is known to be non-cariogenic. Moreover, it is rapidly absorbed in the small intestine and quantitatively excreted in the urine. Only about 10 % enters the colon. Earlier in vitro experiments showed that erythritol remained unfermented for a fermentation period of 12 h. In order to investigate whether fresh human intestinal microbiota is able to adapt its enzyme activities to erythritol, a 24 h lasting fermentation was carried out under well-standardised in vitro conditions. For comparison maltitol, lactulose and blank (faecal inoculum only) were incubated as well. Fermentation patterns were established by following total gas production, hydrogen accumulation, changes in pH value, SCFA production and substrate degradation. Taking all fermentation parameters into account, erythritol turned out to be completely resistant to bacterial attack within 24 h, thus excluding an adaptation within that period. Since under in vivo conditions more easily fermentable substrates enter the colon continuously, it seems very unlikely that erythritol will be fermented in vivo.

The properties of commercial directly and indirectly heated UHT milks, both after heating and during storage at room temperature for 24 weeks, were studied. Thermally induced changes were examined by changes in lactulose, furosine and acid-soluble whey proteins. The results confirmed previous reports that directly heated UHT milks suffer less heat damage than indirectly heated milk. During storage, furosine increased and bovine serum albumin in directly heat-treated milks decreased significantly. The changes in lactulose, α-lactalbumin and β-lactoglobulin were not statistically significant. The data suggest that heat treatment indicators should be measured as soon as possible after processing to avoid any misinterpretations of the intensity of the heat treatment.

In the context of the general applicability of hydroxymethylfurfural (HMF), lactulose and furosine as time-temperature integrators (TTIs) for thermal processing of milk, the influence of milk fat content was studied. Formation kinetics were analysed for milk with fat content of 4·0±<0·1%. In previous experiments, it was observed that, under isothermal and non-isothermal heating conditions, formation of the three chemical compounds could be described by pseudo-zero order kinetics. Since the kinetic model was known, the experimental design could be simplified. Data were analysed by a non-linear regression procedure and results were evaluated by construction of joint confidence regions and temperature time tolerance (TTT-) diagrams. Formation kinetics of HMF and lactulose was not affected by milk fat content. Regarding furosine, significant differences were observed between kinetic parameters in whole, semi-skimmed and skimmed milk. The observed differences however were negligible in the context of process impact evaluation.

A detailed kinetic study of hydroxymethylfurfural, lactulose and furosine formation was performed upon heating milk at temperatures between 90 °C and 140 °C. In case of prolonged heating, formation kinetics could be described by a fractional conversion model. Considering only the first phase of the model, kinetics could be simplified to a pseudo-zero order model. A first assessment of kinetic parameters was made by isothermal experiments. Data were analysed using both a 2-step linear and a 1-step non-linear regression method. Only for furosine, did the global 1-step regression approach seem to give better results than the individual 2-step regression approach. Next, the estimated parameters kref and Ea were re-evaluated under non-isothermal conditions by subjecting milk to a time variable temperature profile. Given the complexity of Maillard reaction, it seemed better to estimate kinetic parameters under non-isothermal conditions when using a simplified model. Formation of hydroxymethylfurfural, lactulose and furosine was characterized by an Ea value of 90·2 kJ/mol (k110 °C = 1·2 μmol/l, min), 99·1 kJ/mol (k110 °C = 51·5 mg/l, min) and 88·7 kJ/mol (k110 °C = 16·3 mg/100 g protein, min) respectively. Additionally, 90% joint confidence regions were constructed in order to obtain an accurate representation of the statistical confidence associated with the simultaneously estimated parameters.

The hypothesis was tested that dietary lactose v. glucose stimulates Mg absorption in rats because lactose lowers pH of the ileal lumen, which improves Mg solubility which in turn enhances Mg availability for transport across the ileal epithelium. For comparison, the effects of lactulose were studied because it shares with lactose the characteristic of being poorly digestible. Replacement of glucose by lactose (100 g/Kg) significantly stimulated apparent absorption of Mg. Apart from Mg absorption, lactulose also significantly enhanced absorption of Ca and phosphate. Lactose v. glucose lowered the pH of the ileal lumen from 7·5 to 7·2, whereas lactulose significantly reduced it to 7·0. In in vitro incubations a decrease in pH within the range of fluctuation in vivo was found to cause an improved solubility of Mg, and to a lesser extent also of Ca and phosphate. The smaller fall of ileal pH induced by feeding lactose instead of lactulose may explain why lactose improved Mg absorption only. For all individual rats combined there were negative relationships between ileal pH and apparent absorption of minerals, the relationship being strongest for Mg. Neither lactose nor lactulose was found to raise ileal solubility of minerals, which could relate to the possibility that the time of sampling was not appropriate. It is suggested that lactose-induced stimulation of Mg absorption in rats is caused by a lowering of ileal pH.