Use of lactulose as a prebiotic in laying hens: its effect on growth, egg production, egg quality, blood biochemistry, digestive enzymes, gene expression and intestinal morphology.

BACKGROUND: The rising popularity of eggs as an alternative source of protein to meat has led to significant increase in egg consumption over the past decade. To meet the increasing demand for eggs, poultry farmers have used antibiotics to treat infections and, to some extent, promote growth and egg production in raising layer. However, the emergence and global spread of antibiotic resistant bacteria has now necessitated antibiotic-free poultry farming. As alternatives to antibiotics, prebiotics are feed additives that can be used to improve the growth and laying performance of poultry which positively impacts their performance and general health. In this study we evaluated the effect of lactulose, formulated as Vetelact, on body weight, egg production, egg quality, blood biochemical parameters and expression of genes associated with reproductive performance in laying hens. RESULTS: Vetelact supplementation improved egg weight, egg production as well as egg quality. Following Vetalact supplementation, the levels of total bilirubin, total protein, globulin and phosphorus were increased, while the activities of alkaline phosphatase and lipase enzymes were increased compared to control. Vetelact at 0.10 ml/kg body weight upregulated OCX-36, OVAL, CALB1, OC-116, OCX-32 and IL8 transcripts while downregulating the transcription of Gal-10, PENK and AvBD9. At this optimal inclusion rate of Vetalect, histomorphologic analyses of intestinal tissue showed increased villi length with more goblet cell distribution and obvious mucus covering a surface, increase in the depth of intestinal crypts produce digestive enzymes, as well as more developed muscle layer that promote improved nutrient absorption. CONCLUSION: Vetelact at a dose of 0.10 ml/ kg body weight was effective in improving productive performance of laying hens. Adding lactulose (0.10 ml/ kg body weight) to layer diet is recommended to promote growth and improve egg laying performance in antibiotics-free poultry production.

The effect of Cassia fistula L. syrup in geriatrics constipation in comparison with the lactulose: A randomized clinical trial.

ETHNOPHARMACOLOGICAL RELEVANCE: Cassia fistula is widely used in traditional Persian Medicine as a mild laxative. The rate of chronic constipation increases above the age of 60. AIM OF THE STUDY: This study aimed to investigate the effect of Cassia fistula syrup (CFS) on geriatric constipation. MATERIALS AND METHODS: This clinical trial study was performed on 70 aged patients who were referred to the clinic of gastroenterology of Rouhani Hospital, Babol, North of Iran. Patients were randomly divided into two groups of CFS or Lactulose with a dose of 30 ccs/day. Patients were visited two weeks after entering the study to evaluate the frequency of defecation, feeling of incomplete emptying after defecation, manual maneuver, consistency of stool, and also the quality of life. RESULTS: The frequency of defecation per week varied from 1.82 ± 1.16 to 8.36 ± 3.44 in the CFS group after 2 weeks of intervention that was significantly more than the Lactulose that changed from 2.16 ± 1.46 to 5.66 ± 2.96 (P-value = 0.023, partial eta square = 0.079, NNT = 4). The quality of life, the percent of straining, lumpy or hard stool, pain during defecation, and the consistency of stool based on VAS were significantly better in the CFS group. The sensation of incomplete defecation, anorectal obstruction, and manual maneuvering were not different significantly between groups. CONCLUSION: CFS can be more effective than Lactulose on geriatric constipation.

Immunomodulatory influences of sialylated lactuloses in mice.

The aim of this study was to investigate the immune modulatory influences of sialylated lactuloses in mice. The effects of the four sialylated lactuloses by gavage methods on the weight gain rate, organ, serum and spleen immunoglobulin of mice were investigated. Neu5Ac-α2,3-lactulose group and Kdn-α2,3-lactulose group had significantly higher weight gain rate than control group. The weight gain rate, thymus index and spleen index of Kdn-α2,3-lactulose group were significantly higher than control group and lactulose group. Liver and small intestine of Neu5Ac-α2,3-lactulose group, Neu5Ac-α2,6-lactulose group and Kdn-α2,6-lactulose group showed different degree of damage. IgG levels of serum and spleen in Neu5Ac-α2,6-lactulose group and Kdn-α2,6-lactulose group were significantly higher than control group and lactulose group. The contents of IgG in serum and spleen of Kdn-α2,3-lactulose group were significantly lower than that of control group, while the contents of IgA and IgM in serum were significantly higher than those of control group. The IgA level increased by 12.23% and 58.77% comparing with lactulose group and control group, respectively. The IgM level in serum of Kdn-α2,3-lactulose group mice increased by 43.88% and 8.05% comparing with control group and lactulose group, respectively. The IgA level and IgM level in spleen of Kdn-α2,3-lactulose group mice increased by 49.05% and 47.25% comparing with control group. In short, Kdn-α2,3-lactulose is relatively safe and superior to use as a food supplement or potential drug candidate. Our results also indicate that some other sialylated oligosaccharides are potentially harmful to organisms, they may cause some side effects.

A Comparative Study of Four Oral Contrast Agents for Small Bowel Distension with Computed Tomography Enterography.

PURPOSE: To assess the efficacy of a variety of oral contrast agents in obtaining small bowel distention for computed tomography (CT) enterography examinations. METHODS: A retrospective study was developed to quantitatively assess small bowel luminal distension during CT enterography by using 4 contrast agents, which included water, Metamucil, polyethylene glycol, and lactulose. A total of 256 patients were enrolled in the study and included 64 individuals for each oral regimen. The widest loop of small bowel in each of 4 quadrants on representative coronal images was separately measured for luminal distension. Overall distension and the greatest number of "useful" quadrants were evaluated. Overall distension was calculated by summing the 4 quadrant values into an overall luminal diameter distention score (cm). A "useful" quadrant was defined as having a measurement of ≥2 cm. Each "useful" quadrant was assigned a score of 1, with values that ranged from 0-4. RESULTS: For overall distension, multivariable liner regression analysis showed that the lactulose group had a significantly higher overall distension value than Metamucil, polyethylene glycol, and water by 0.88, 0.92, and 1.63 cm, respectively, with 95% confidence interval. The categorical multivariable logistic regression analysis showed that the lactulose group had greater odds of having more "useful" quadrants than the Metamucil, polyethylene glycol, and water groups, with odds ratios of 3.51, 2.68, and 9.19, respectively. CONCLUSION: Lactulose achieves better small bowel distension for CT enterography studies than the other 3 agents and, therefore, is the preferred oral regimen at our institution.

Lactulose increases equol production and improves liver antioxidant status in barrows treated with Daidzein.

Equol, one of the intestinal microflora metabolites of daidzein, has gained much attention for having greater bioactivity than its precursor (daidzein and daidzin) and seeming to be promoted by hydrogen gas. The effects of lactulose on the equol-producing capacity and liver antioxidant status of barrows treated with daidzein were investigated in this study. Male castrated piglets (barrows) of Landrace × Duroc, aged 40 days, were randomly divided into the following three groups: control group (C, n = 12, fed an isoflavones-free basic diet), daidzein group (D, n = 12, fed an isoflavones-free basic diet with 50 mg/kg of daidzein supplementation) and daidzein+lactulose group (D+L, n = 12, fed an isoflavones-free basic diet with 1% of lactulose and 50 mg/kg of daidzein supplementation). After 20 days, the profile of short-chain fatty acids in the colon digesta showed that lactulose significantly increased the fermented capacity in the gastrointestinal tract of the barrows. First-void urinary equol concentrations were significantly higher in the D+L group than in the D group (3.13 ± 0.93 compared to 2.11 ± 0.82 µg/ml, respectively). Furthermore, fecal equol levels were also significantly higher in the D+L group than in the D group (12.00 ± 2.68 compared to 10.00 ± 2.26 µg/g, respectively). The population of bacteroidetes and the percentage of bacteroidetes to bacteria in feces were higher in the D+L group than in the D group. The DGGE profiles results indicate that lactulose might shift the pathways of hydrogen utilization, and changing the profiles of SRB in feces. Moreover, the D+L group had weak enhancement of T-SOD and CuZn-SOD activities in the livers of barrows treated with daidzein.

Effects of lactulose supplementation on performance, blood profiles, excreta microbial shedding of Lactobacillus and Escherichia coli, relative organ weight and excreta noxious gas contents in broilers.

This study was to evaluate the effects of lactulose supplementation on performance, blood profiles, excreta microbial shedding of Lactobacillus and Escherichia coli, relative organ weight and excreta noxious gas contents in broilers. A total of 720 ROSS 308 broilers with a body weight of 46 ± 0.1 g (1 day of age) were used in a 28-d experiment. Broilers were randomly allotted to 4 experiment diets with 12 replicate pens and 15 birds per pen. Dietary treatments were as follows: NC, negative control (without antibiotic); PC, NC + 0.1% tiamulin; L1, NC + 0.1% lactulose; and L2, NC + 0.2% lactulose. Broilers were fed with phase 1 (1-8 day), phase 2 (9-18 day) and phase 3 (19-28 day) diets in the form of mash. During day 1-8, broilers fed the PC and L2 diets had higher (p < 0.05) body weight gain than those fed the NC diet. During day 19-28, broilers fed the L1 and L2 diets had lower (p < 0.05) feed intake than those fed the NC diet. The feed conversion ratio (FCR) was decreased (p < 0.05) in L1 treatment compared with NC treatment. Overall, the FCR was improved (p < 0.05) in all supplementation treatments compared with NC treatment. The apparently metabolizable nitrogen in L1 treatment was higher (p < 0.05) than that in NC treatment at day 28. The excreta Lactobacillus was increased and E. coli was decreased in PC and L2 treatments compared with NC treatment at day 28 (p < 0.05). The excreta NH3, H2S and acetic acid contents were decreased (p < 0.05) in L1 and L2 treatments compared with NC treatment. The relative weight of abdominal fat of broilers fed the PC diet was lowest (p < 0.05) compared with other treatments. In conclusion, this study indicated that dietary supplementation of 0.1% or 0.2% lactulose could improve growth performance, decrease excreta E. coli and excreta NH3 and H2S contents.

Efficacy and side-effect profiles of lactulose, docusate sodium, and sennosides compared to PEG in opioid-induced constipation: a systematic review.

UNLABELLED: Opioid-induced constipation (OIC) is a side effect of opioid therapy that can affect quality of life, adherence to treatment, and morbidity and possibly mortality. OBJECTIVES: To investigate whether docusate sodium, sennosides, and lactulose have equal efficacy and side effect profiles compared to PEG in the management of OIC in adults. METHODS: A systematic review was undertaken. Randomized controlled trials of adults taking opioids for cancer or non-cancer pain were considered if they met inclusion criteria. CONCLUSIONS: Statistical pooling was not possible as no studies met inclusion criteria. Large, well-powered, randomized controlled trials are feasible. Standard definitions of OIC would assist with the execution of these studies and contribute to their internal and external validity. Further research is strongly encouraged.

Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study.

OBJECTIVE: The study objective was to assess the effects and tolerability of two novel natural medicine formulations in improving bowel habit and abdominal symptoms in patients with irritable bowel syndrome (IBS). The DA-IBS formula was designed to treat diarrhea-predominant and alternating bowel habit IBS, and the C-IBS formula was designed to treat constipation-predominant IBS. DESIGN: This was a two arm, open-label, uncontrolled pilot study. SETTINGS/LOCATION: Subjects were recruited from the greater Lismore area (NSW, Australia) in 2001. SUBJECTS: The study included 31 patients who fulfilled the Rome II criteria for IBS. Twenty-one (21) patients were classified as suffering from diarrhea-predominant or alternating bowel habit IBS and 10 patients were classified with constipation-predominant IBS. INTERVENTIONS: The DA-IBS formula consisted of a mixture of dried, powdered bilberry fruit, slippery elm bark, agrimony aerial parts, and cinnamon quills. The C-IBS formula consisted of a mixture of dried powdered slippery elm bark, lactulose, oat bran, and licorice root. The aim of each formula was to normalize stool frequency and stool consistency. RESULTS: Ingestion of the DA-IBS formula was associated with a small, but significant increase in bowel movement frequency (p = 0.027). Subjects in the DA-IBS group also experienced reductions in straining (p = 0.004), abdominal pain (p = 0.006), bloating (p < 0.0001), flatulence (p = 0.0001), and global IBS symptoms (p = 0.002) during the treatment phase of the trial. Subjects in the C-IBS group experienced a 20% increase in bowel movement frequency (p = 0.016) and significant reductions in straining (p < 0.0001), abdominal pain (p = 0.032), bloating (p = 0.034), and global IBS symptom severity (p = 0.0005), as well as improvements in stool consistency (p < 0.0001). Both formulas were well-tolerated. CONCLUSIONS: The DA-IBS formula was not effective in improving bowel habit in individuals with diarrhea-predominant or alternating bowel habit IBS, although it did significantly improve a number of IBS symptoms. The C-IBS formula significantly improved both bowel habit and IBS symptoms in patients with constipation-predominant IBS. Further research is warranted on C-IBS, as a potentially useful therapeutic formula.

Gastric emptying and orocaecal transit time of meals containing lactulose or inulin in men.

The H(2) 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 H(2) 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 (13)C-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 H(2) breath test.

Pharmacological treatments and strategies for reducing oral and intestinal acetaldehyde.

Strong epidemiological, genetic and biochemical evidence indicates that local acetaldehyde exposure is a major factor behind gastrointestinal cancers especially associated with alcohol drinking and smoking. Thus, reducing the exposure to carcinogenic acetaldehyde either by decreasing the production or by eliminating acetaldehyde locally might offer a preventive strategy against acetaldehyde-induced gastrointestinal cancers. Thiol products, such as the amino acid cysteine, are known to be able to protect against acetaldehyde toxicity. Cysteine is able to bind acetaldehyde efficiently by forming a stable thiazolidine-carboxylic acid compound. Special cysteine preparations (such as lozenge and chewing gum) have already been developed to bind smoking and alcohol drinking derived acetaldehyde from the oral cavity. Most importantly, these type of drug formulations offer a novel method for intervention studies aimed to resolve the eventual role of acetaldehyde in the pathogenesis of upper digestive tract cancers. Acetaldehyde exposure could also be influenced by modifying the acetaldehyde producing microbiota. With regard to the upper digestive tract, acetaldehyde production from ingested ethanol could be significantly reduced by using an antiseptic mouthwash, chlorhexidine. In the large intestine acetaldehyde production could be markedly decreased either by reducing the Gram-negative microbes by ciprofloxacin antibiotic or by lowering the intraluminal pH by lactulose.

Low-dose lactulose produces a tonic contraction in the human colon.

Lactulose (10-20 g day(-1)) is used to treat constipation. At this therapeutic dose, its effects on colonic motility remain unknown. Twenty-two healthy subjects swallowed a probe with an infusion catheter, six perfused catheters and a balloon connected to a barostat. Colonic phasic and tonic motor activity was recorded in fasting state. In group 1, four volunteers ingested 15 g lactulose and motility was recorded for 5 h after entry of lactulose into the caecum; in group 2, motility was recorded during (3 h) and 2 h after intracolonic infusion of isoosmotic and isovolumetric solutions containing sodium chloride alone (n = 9) or with 15 g lactulose (n = 9). In a last group of volunteers, isotopic colonic transit after ingestion of lactulose (10 g,n = 9) was assessed and compared with a control group (n = 17). Ingestion or intracolonic infusion of 15 g lactulose significantly decreased barostat bag volume (maximal decrease: 45 +/- 12% and 35 +/- 9% of basal value respectively). Phasic contractions remained unchanged. Tonic and phasic motility was unchanged by the isotonic and isovolumetric infusion of saline. Ingestion of lactulose significantly accelerated isotopic colonic transit time compared with the control group. We conclude that in healthy humans, 10-15 g ingestion or intracaecal infusion of lactulose produces a prolonged tonic contraction that may be involved in the laxative effect of lactulose.

Effect of the herbal medicine Dai-kenchu-to for serum ammonia in hepatectomized patients.

BACKGROUND/AIMS: Prolonged paralytic ileus occurring in hepatectomized patients may induce hyperammonemia or bacterial translocation, which injures the remnant liver function and sometimes causes post-resection liver failure. We examined the effectiveness of the herbal medicine, Dai-kenchu-to (DKT), on postoperative serum ammonia levels in patients with liver resection and compared it with lactulose. METHODOLOGY: Patients with liver resection were divided into three groups. Lactulose group (n=31), 16g of lactulose was administered orally three times a day from the first postoperative day. DKT group (n=27), 5g of DKT was administered in the same fashion. Control group (n=26), neither lactulose nor DKT was administered. In all three groups, 16g of lactulose was administered three times a day for three days preoperatively. RESULTS: There was no significant difference among the groups in age, gender and preoperative hepatic functional values, such as ICG-R15 or galactose tolerance test. There was also no difference in parenchymal hepatic resection rate, operative time and amount of intraoperative bleeding volume. Postoperative serum ammonia levels were significantly lower in the DKT group than control and lactulose groups. Instances of delayed flatulence and occurrence of diarrhea were also fewer in the DKT group. CONCLUSIONS: DKT may become a more effective and safe agent than lactulose in postoperative management of liver resection.

Neostigmine for the treatment of acute hepatic encephalopathy with acute intestinal pseudo-obstruction in a cirrhotic patient.

We treated a 49-yr-old man with neostigmine, who had liver cirrhosis, acute hepatic encephalopathy, and acute intestinal pseudoobstruction. He was admitted in a state of hepatic confusion. On physical examination, the abdomen was distended; and bowel sound was absent. Plain abdomen film revealed multiple air-fluid levels and distention of bowel loops. Initially, we gave him lactulose enemas every 6 hr for one day without improvement in his mental state. Furthermore, he became to a state of coma. Therefore, we gave him 0.5 mg of neostigmine subcutaneously to improve his peristaltic movement, and 2 L of polyethylene glycol electrolyte solution through a nasogastric tube for 4 hr to reduce the production and absorption of gut-derived toxins of nitrogenous compounds. After these treatments, the venous ammonia level decreased to the normal range within 12 hr, and the coma disappeared after 2 days. We suggest that neostigmine may be one of the most effective treatments to initiate peristaltic movement and bowel cleansing in cirrhotic patients with acute hepatic encephalopathy and acute intestinal pseudoobstruction.

Neostigmine for the Treatment of Acute Hepatic Encephalopathy with Acute Intestinal Pseudo-obstruction in a Cirrhotic Patient

We treated a 49-yr-old man with neostigmine, who had liver cirrhosis, acute hepatic encephalopathy, and acute intestinal pseudoobstruction. He was admitted in a state of hepatic confusion. On physical examination, the abdomen was distended; and bowel sound was absent. Plain abdomen film revealed multiple airfluid levels and distention of bowel loops. Initially, we gave him lactulose enemas every 6 hr for one day without improvement in his mental state. Furthermore, he became to a state of coma. Therefore, we gave him 0.5 mg of neostigmine subcutaneously to improve his peristaltic movement, and 2 L of polyethylene glycol electrolyte solution through a nasogastric tube for 4 hr to reduce the production and absorption of gutderived toxins of nitrogenous compounds. After these treatments, the venous ammonia level decreased to the normal range within 12 hr, and the coma disappeared after 2 days. We suggest that neostigmine may be one of the most effective treatments to initiate peristaltic movement and bowel cleansing in cirrhotic patients with acute hepatic encephalopathy and acute intestinal pseudoobstruction.

Effect of acute dietary fibre supplementation on colonic pH in healthy volunteers.

Dietary fibre and undigested starch are fermented to short chain fatty acids by colonic bacteria with acidification of the colon. It has been suggested that acidification of the colon by these fatty acids inhibits bacterial metabolism, but this concept has been disputed. The aim of this study was to investigate the short term effect of a dietary fibre load on colonic metabolism. Colonic pH and breath hydrogen was measured in healthy omnivorous British male volunteers following ingestion, in turn and at weekly intervals, of 15g lactulose, wheat bran biscuits, oat bran biscuits and ispaghula husk. All the test meals caused a reduction in caecal pH and an increase in breath hydrogen production. The changes were greatest with lactulose. Lactulose and wheat bran caused acidification of the right and left colon whereas oat bran and ispaghula husk caused acidification of mainly the right colon. An inverse correlation between right colonic pH and breath hydrogen was observed in only the oat bran study. This study has demonstrated the ability of dietary fibre to lower right colonic pH and to increase breath hydrogen excretion. The changes were greater with soluble fibre than with insoluble fibre but the change in luminal pH was persistent all round the colon with insoluble fibre.

Effect of lactulose on short-chain fatty acids and lactate production and on the growth of faecal flora, with special reference to Clostridium difficile.

Lactulose exerts a beneficial effect on hepatic encephalopathy by decreasing toxic short-chain (iC4-nC6) fatty acid (isobutyrate, butyrate, isovalerate, valerate, isocaproate and caproate) production. However, the precise mechanism by which lactulose exerts this effect remains uncertain. This study investigated the effect of lactulose on faecal flora, particularly Clostridium difficile, which produces mostly iC4-nC6 fatty acids. An in-vitro faecal incubation system was used to estimate how lactulose influences production of short-chain (C2-nC6) fatty acids and lactate. Faecal specimens were collected from patients with liver cirrhosis, who carried C. difficile in the colon. Supplementation of lactulose along with blood in faecal specimens decreased iC4-nC6 fatty acids production and increased acetate and lactate production, resulting in increased faecal acidity. These changes were statistically significant when compared with supplementation by blood alone. Quantitative faecal culture demonstrated that lactulose supplementation suppressed the growth of C. difficile and Bacteroides spp. (B. fragilis group), iC4-nC6 fatty acids-producing organisms. These results suggest that decreased faecal levels of iC4-nC6 fatty acids after lactulose supplementation may be related to suppression of iC4-nC6 fatty acids-producing faecal organisms, especially C. difficile.

Availability of calcium for absorption in the small intestine and colon from diets containing available and unavailable carbohydrates: an in vitro assessment.

An in vitro method simulating conditions in the small intestine and colon was used to study the effects of various carbohydrates on Ca release from basal diet (BD) containing dairy products. During enzymatic digestion of BD, 28.5 +/- 0.3% of the Ca was released. This was reduced by 3, 22 and 27% by adding bread, psyllium or pectin to BD, respectively (P < 0.05). After enzymatic digestion, the residue from BD was fermented releasing 11.9 +/- 1.2% of the Ca, a value which was significantly less than with pectin (13.7 +/- 0.9%) and greater than with psyllium (4.4 +/- 0.2%) addition. The total Ca release ranged from 26.5 +/- 0.8 to 42.2 +/- 1.0% with bread>BD>pectin>psyllium. Lactulose did not differ significantly from BD. These results suggest that carbohydrates may bind Ca and reduce its availability for absorption in the small intestine. However, if the carbohydrate is fermented, bound Ca may be released for potential absorption in the colon, whereas less fermented carbohydrates may continue to bind Ca in the colon. The in vitro method described may be useful for estimating total Ca availability. However, studies in humans are required to validate these results.

Effects of feeding fermentable carbohydrates on the cecal concentrations of minerals and their fluxes between the cecum and blood plasma in the rat.

This study was conducted to determine in rats to what extent fermentable carbohydrates alter the mineral composition of cecal contents and the absorption of the major cations. The carbohydrates studied were as follows: an oligosaccharide (lactulose, 10%); a soluble fiber (pectin, 10%); and an amylose-rich starch, incompletely broken down in the small intestine (amylomaize starch, 25 or 50%). All of these carbohydrates elicited a marked enlargement of the cecum, a drop of cecal pH and an increase in the volatile fatty acids (VFA) pool. With the lactulose diet, the VFA concentration was the lowest, whereas VFA absorption was similar to that observed with the 10% pectin or 25% amylomaize diets. From comparisons between germfree and conventional rats adapted to a fiber-free diet, it appears that VFA are required as counter anions to maintain high concentrations of cations, especially sodium. In conventional rats fed fermentable carbohydrates, sodium concentration in the cecal fluid was approximately 80 mM, except with the lactulose diet (49.5 mM), due to osmotic effects of lactulose. There was, compared to the fiber-free diet, an increase in the cecal concentrations of potassium, calcium and phosphate, but not of magnesium; nevertheless, the cecal pool of all of these minerals was considerably increased. Potassium absorption was increased by fermentable carbohydrates in the cecum, which also appears to be a major site of magnesium and calcium absorption. Thus, fermentable carbohydrates shift aborally the absorption of the major cations, and this point is especially interesting in regard to calcium, since an enhanced supply of calcium in the large bowel has been invoked for fiber effects on colonic carcinogenesis.

Specific effects of fermentable carbohydrates on blood urea flux and ammonia absorption in the rat cecum.

These studies were conducted to determine to what extent dietary fibers, or related compounds such as lactulose or amylomaize starch, alter the flux of blood urea to the cecum and cecal absorption of ammonia in the rat. Cecal weight and pH values were not different among rats fed diets containing 10% lactulose, pectin or guar gum, or 25% amylomaize starch. However, the cecal wall weight was markedly higher with lactulose feeding than with the other polysaccharides, whereas volatile fatty acid concentrations were lower with lactulose. The fiber diets depressed cecal ammonia, particularly in the case of the amylomaize starch diet, whereas the lactulose diet enhanced the concentration of ammonia. Owing to cecal enlargement and enhanced blood flow, the diets containing fermentable carbohydrates promoted a higher flux of urea to the cecum and also higher ammonia absorption in spite of low concentrations of ammonia in the cecum. Lactulose led to particularly high transfer of urea and absorption of ammonia. High blood urea in rats fed a 50% casein diet led to a very high flux of urea to the cecum and, hence, to high ammonia absorption. The presence of polysaccharides amplified the flux of urea and ammonia in the cecum. This study suggests that oligosaccharides such as lactulose, although very effective for the acidification of the contents of the large intestine, may enhance cecal ammonia and its absorption. Polysaccharides such as amylomaize starch might show greater efficiency for lowering ammonia concentrations in the large intestine.