Impairment of Starch Absorption by a Potent Amylase Inhibitor

Many previous investigations of available amylase inhibitors have not been able to demonstrate significant carbohydrate malabsorption. This study uses breath hydrogen analysis, a sensitive method for detecting the passage of starch into the colon, to determine if a potent amylase inhibitor is capable of producing carbohydrate malabsorption. Thirteen volunteers underwent three studies, ingesting as a carbohydrate substrate: lactulose 20 g, spaghetti alone, and spaghetti with amylase inhibitor (3.8 g). Samples of breath were collected (at frequent intervals) for 2 h after the lactulose and for 8 h after the spaghetti meal and analyzed for hydrogen concentration. The ingestion of spaghetti alone resulted in significant increases in breath hydrogen concentration at 420-450 min. The mean (+/- SE) hydrogen excretion rate was increased more than 2-fold with the amylase inhibitor, from 0.4 +/- 0.2 to 0.9 +/- 0.3 ml/h (p less than 0.05). Use of the amylase inhibitor in powder form produced a similar increase in the rate of hydrogen excretion to 1.1 +/- 0.4 ml/h. The percentage of carbohydrate malabsorbed was calculated for the spaghetti meal and spaghetti with amylase inhibitor using each individual's observed hydrogen excretion with lactulose. Over the 8-h observation period, 4.7 +/- 1.9% of the spaghetti was malabsorbed and 7.0 +/- 1.4% of the spaghetti with amylase inhibitor was malabsorbed (p less than 0.05). Measurements of the effect of the amylase inhibitor on amylase activity of duodenal juice revealed that the amylase inhibitor at a concentration of more than 5 mg/ml decreased the amylase activity by more than 96%. These results indicate that this potent amylase inhibitor is capable of enhancing malabsorption of wheat starch.     

Absorption of wheat starch in patients resected for left-sided colonic cancer.

Bacterial fermentation of carbohydrate in the colon, producing short-chain fatty acids (SCFA)--and especially butyrate--has been shown possibly to impede cell proliferation and regulate cell differentiation of colonocytes. In patients with diverticular disease or benign polyps in the colon a hyperabsorption of potato starch in the small intestine has been found. We have investigated the absorption of wheat starch in 15 patients radically resected for cancer in the descending or sigmoid colon, and the results were compared with those of 15 healthy controls. The starch malabsorption was quantified by the hydrogen breath test. The patients malabsorbed 2-14 g (median, 8 g) of 100 g wheat starch ingested, and the control group malabsorbed 3-11 g (median, 6 g) (P greater than 0.1). Mouth-to-cecum transit time for wheat starch and lactulose and the hydrogen production capacity after the lactulose standards were also similar in patients and controls. The results do not support the theory that hyperabsorption of starch is characteristic of patients with malignant disease in the large intestine.     

Is raised breath hydrogen related to the pathogenesis of pneumatosis coli?

Clinical and physiological studies were carried out in five patients with pneumatosis coli in order to investigate the origin of the high fasting breath hydrogen concentration in this condition and to determine its possible significance in the pathogenesis of the disease. All five patients excreted abnormally high fasting concentrations of hydrogen in their breath (69 +/- 9 ppm, mean +/- SEM). Moreover, analysis of the contents of the gas filled cysts revealed between 2% and 8% of hydrogen gas. Colonic washout significantly reduced breath hydrogen concentrations to 9 +/- 6 ppm, but did not abolish the cysts. Conversely, deflation of the cysts was achieved with oxygen or antibiotics, though this only reduced breath hydrogen concentrations to about 66% of their original value. After feeding a radiolabelled meal, breath hydrogen concentrations rose before the meal appeared to reach the colon, suggesting overgrowth of anaerobic bacteria in the small intestine. Despite this, 14C glycocholate breath tests were within normal limits. An alternative possibility is that the high levels of hydrogen excreted in the breath may be produced in the intestinal lumen possibly from the fermentation of copious amounts of colonic mucus. Finally, measurement of whole gut transit time and stool weight suggested that patients were constipated despite passing mucus and blood. The relevance of our observations to the pathogenesis of submucosal cysts is unclear, but the data favour the hypothesis that these are produced by invasion of the colonic submucosa with anaerobic bacteria.     

Lactose malabsorption in Greek adults: correlation of small bowel transit time with the severity of lactose intolerance.

Using breath hydrogen analysis after 139 mmol (50 g) oral lactose load, we investigated the prevalence of lactose malabsorption in 200 Greek adults and examined the relationship between symptoms and small bowel transit time. One hundred and fifty subjects had increased breath hydrogen concentrations (greater than 20 ppm) after the lactose load. In these individuals peak breath hydrogen concentration was inversely related to small bowel transit time (r = 0.63, 6 = 6.854, p less than 0.001) and the severity of symptoms decreased with increasing small bowel transit time. Lactose malabsorbers with diarrhoea during the lactose tolerance test had a small bowel transit time of 51 +/- 22 minutes (x +/- SD; n = 90) which was significantly shorter than the small bowel transit time of patients with colicky pain, flatulence, and abdominal distension (74 +/- 30, n = 53; p less than 0.001) and both groups had significantly shorter small bowel transit time than that of asymptomatic malabsorbers (115 +/- 21 n:7; p less than 0.001). When the oral lactose load was reduced to 33 mmol (12 g), the small bowel transit time increased five-fold and the overall incidence of diarrhoea and/or symptoms decreased dramatically. These results indicate that the prevalence of lactase deficiency in Greece may be as high as 75% and suggest that symptom production in lactose malabsorbers is brought about by the rapid passage down the small intestine of the malabsorbed lactose.     

Complex carbohydrate malabsorption in exocrine pancreatic insufficiency.

The magnitude of complex carbohydrate malabsorption in exocrine pancreatic insufficiency has not been well quantified in the past. The quantity of carbohydrate malabsorbed after a rice starch (100 g) meal in 20 patients with chronic pancreatitis (n = 10) or pancreatic cancer (n = 10) was therefore estimated. Patients had a three day stool fat collection (80 g/24 hour fat intake), a lactulose (20 g), and a rice flour (100 g) breath hydrogen test. Normal controls (n = 29) had a postprandial H2 increase < or = 14 ppm and malabsorbed (mean (SEM)) 1.12 (0.44) (range 0-11.10) g of the 100 g of carbohydrate ingested. Patients malabsorbed significantly more carbohydrate (11.36 (2.23) (range 8.90-32.60) g, F1.47 = 29.92, p < 0.001). The number of patients with fat (> 7 g, n = 8) or carbohydrate (increase in H2 > or = 20 ppm, n = 10) malabsorption was not different (chi 2 = 0.10, p = 0.75). There was a significant correlation between faecal fat and amount of malabsorbed carbohydrate (r = 0.60, F1.17 = 9.70, p = 0.006) and faecal fat and stool wet weight (r = 0.57, F1.18 = 8.67, p < 0.009), but not between stool wet weight and amount of malabsorbed carbohydrate (r = 0.28, F1.17 = 1.45, p = 0.25). Although patients with exocrine pancreatic insufficiency malabsorb 10%-30% of the ingested complex carbohydrate, the main determinant of stool wet weight could be faecal fat.     

Absorption of Wheat Starch in Patients Resected for Left-Sided Colonic Cancer

Bacterial fermentation of carbohydrate in the colon, producing short-chain fatty acids (SCFA)–and especially butyrate–has been shown possibly to impede cell proliferation and regulate cell differentiation of colonocytes. In patients with diverticular disease or benign polyps in the colon a hyperabsorption of potato starch in the small intestine has been found. We have investigated the absorption of wheat starch in 15 patients radically resected for cancer in the descending or sigmoid colon, and the results were compared with those of 15 healthy controls. The starch malabsorption was quantified by the hydrogen breath test. The patients malabsorbed 2-14 g (median, 8g) of 100 g wheat starch ingested, and the control group malabsorbed 3-11 g (median, 6 g) (P > 0.1). Mouth-to-cecum transit time for wheat starch and lactulose and the hydrogen production capacity after the lactulose standards were also similar in patients and controls. The results do not support the theory that hyperabsorption of starch is characteristic of patients with malignant disease in the large intestine     

Simultaneous measurement of gastric emptying, small bowel residence and colonic filling of a solid meal by the use of the gamma camera

A method for determining the profiles of gastric emptying, small intestinal residence, and colonic filling of a solid test meal, labelled with 250 microCi 99mTechnetium sulphur colloid has been evaluated in nine healthy volunteers and six patients with a disturbance in bowel habit. Mean small bowel transit time was determined by deconvolving the rate of colonic filling with the rate of gastric emptying. In normal subjects, the stomach appeared to empty exponentially with a half time of 1.2 +/- 0.3 hours (mean +/- SD). Food reached the colon by 2.8 +/- 1.5 hours. The mean small bowel transit time was 4.0 +/- 1.4 hours. In most normal subjects, the colon appeared to fill in a linear fashion with approximately 16% food residues entering every hour, and the profile of colonic filling in normal subjects was similar to the profile of ileal emptying observed after feeding a similar radiolabelled solid meal to 14 patients equipped with terminal ileostomies. There was a highly significant correlation between the onset of breath hydrogen excretion and the appearance of radioactivity over the caecum (r = 0.88, p less than 0.01), though in one third of subjects the increase in caecal radioactivity preceded the rise in breath hydrogen concentration by more than 20 minutes. There was also a highly significant correlation between the mean transit time and values for colonic filling but not values for gastric emptying. Patients with irritable bowel syndrome who had diarrhoea tended towards short small bowel transit and early colonic filling, whereas patients who have constipation tended towards long small bowel transit and delayed colonic filling. This method offers a novel means of assessing small bowel transit time, small bowel residence and the profile of colonic filling in man.     

Interpretation of the breath hydrogen profile obtained after ingesting a solid meal containing unabsorbable carbohydrate.

The extent to which monitoring breath hydrogen excretion provides information concerning the entry of the residues of a solid test meal into the colon was investigated in 89 normal subjects, and 11 patients with the irritable bowel syndrome. The profile of breath hydrogen concentration showed an early peak, that occurred soon after ingesting the test meal in 89% subjects. This was followed by a later more prolonged rise in breath hydrogen concentration. The early peak occurred well before a radioactive marker, incorporated in the test meal, reached the caecum and the data suggest it was predominantly caused by the emptying of the remnants of the previous meal from the ileum into the colon. This hypothesis was supported by direct measurements of the rate of delivery of ileostomy effluent in 12 subjects with terminal ileostomies. Fermentation of carbohydrate in the mouth may, however, contribute to the initial peak, but this contribution may be avoided by collecting gas samples from the nares. The secondary rise in breath hydrogen excretion was closely correlated with the arrival of the radioactive marker in the caecum (r = 0.91), p less than 0.001), though the time, at which the secondary peak of breath hydrogen excretion occurred was poorly correlated with the time that all the radioactive test meal had entered the colon. When lactulose was infused directly into the colon, as little as 0.5 g produced a discernible hydrogen response, which occurred within two minutes of the infusion. Increasing the rate of colonic infusion of a 50 ml solution of 10% lactulose from 0.02 to 0.15 g/min in five subjects significantly increased the breath hydrogen concentration. At infusion rates below 0.075 g lactulose/minute, the peak breath hydrogen response preceded the end ot the infusion, while at higher rates of infusion, the peak hydrogen response occurred after the end of the infusion. Although these results confirmed that monitoring breath hydrogen concentration usefully signalled the time taken for a meal containing unabsorbed carbohydrate to reach the colon, it did not reliably indicate the time when all of the meal had entered the colon. Finally, the use of the maximum increase in breath hydrogen concentration as an index of the degree of carbohydrate malabsorption assumes uniform rates of entry into the colon.     

Lactase deficiency and lactose intolerance-related symptoms in adult healthy subjects from western France]

The prevalence of lactase deficiency (LD) and lactose intolerance is not well known in France. Using breath hydrogen and methane analysis after 50 g oral lactose load, we investigated the prevalences of LD, lactose intolerance, and methane producer status in 102 healthy adults born in western France, and we examined the relationships between these parameters and the daily milk consumption. In 10 subjects with LD and lactose intolerance, we studied the reproducibility of the lactose hydrogen breath test results for the diagnosis of LD and lactose intolerance and estimated the quantity of lactose malabsorbed in comparison with the lactulose hydrogen breath test. The prevalence of LD was 23.4 percent and symptoms of lactose intolerance were observed in 50 percent of the 24 subjects with LD. The daily milk consumption was not significantly different in the 24 subjects with LD and in the 78 subjects without LD (281 +/- 197 vs 303 +/- 217 ml/24 h). The prevalence of methane producer status was 42.1 percent. The symptomatic group of lactose malabsorbers (n = 12) was characterized by a shorter lactose mouth to caecum transit time (39 +/- 20 vs 88 +/- 48 min; P less than 0.05), and more marked hydrogen production (6.1 +/- 2.3 vs 3.4 +/- 2.4 10(3) ppm.min; P less than 0.04). In the 10 subjects with LD and lactose intolerance, the hydrogen breath test was reproducible for diagnosis of LD and lactose intolerance, and for hydrogen production. The quantity of lactose malabsorbed was 60 percent. In France, symptoms of lactose intolerance are not severe and do not affect the daily consumption of milk and dairy products.     

Small bowel transit time and colonic fermentation in young and elderly women

Small bowel transit time (SBTT) in 15 young and 13 elderly women was assessed by measuring breath hydrogen concentrations after they had consumed a solid test meal. The meal consisted of 200 g cooked rice, 50 mlmiso (made from fermented soy bean curd) soup, a boiled egg, and 95.5 g of cooked soy beans with mixed vegetables. This meal provided 17 g protein, 14.1 g fat, 92.9 g carbohydrate, 7 g dietary fiber, and 565 kcal total energy. The SBTT, calculated by a 3 ppm increase in breath hydrogen, was 19±14.9 (mean±SE) min in the young and 188.1±16.8 min in the elderly group; the difference was not significant. Breath hydrogen levels, however, were higher in the young than in the elderly group (39.1±6.3 ppm, vs 22.2±4.3 ppm,P<0.05). There was an initial peak of hydrogen concentration, reached almost immediately after the ingestion of the meal, and then a decline to baseline within 60 min. This initial peak was not as pronounced in the elderly subjects. A second peak, indicating the entry of the test meal into the cecum, was more pronounced in the young than in the elderly group. SBTT did not differ significantly between the two groups, but colonic fermentation was more pronounced in the young, both in the fasting and the postprandial state.     

Mouth to pouch transit after restorative proctocolectomy: hydrogen breath analysis correlates with scintigraphy

OBJECTIVES: Fast intestinal transit may be responsible for slow adaptation and unacceptable steady-state function after restorative proctocolectomy. Investigation of GI transit time may be valuable in such a setting. We hypothesized that postprandial hydrogen breath tests may yield transit data that correlate with technetium-labeled meal scintigrams. METHODS: This study compared intestinal transit after a lactulose and bean meal via the breath hydrogen and scintigraphy methods in 21 ileoanal pouch subjects. The meal consisted of baked beans (425 g), 30 ml (20 g) lactulose syrup, 1 mCi 99mtechnetium sulfur colloid in finely chopped liver and 170 ml tap water. The meal contained 120 Kcal (70% carbohydrate, 18% protein and 12% fat). RESULTS: Of 21 pouch subjects, 11 (53%) had breath tests and scintigraphy transit studies that differed by 5-21 min. Three of 21 (14%) scintigraphy mouth to pouch transit times were faster than breath test transits by 43-107 min. Seven of 21 (33%) subjects did not have breath test peaks >10 ppm. Mouth to pouch transit for breath hydrogen (104+/-16 min) and scintigraphy (98+/-7 min) tests had significant correlation (r = 0.96, p < 0.0001) among subjects with alveolar hydrogen peaks and accurate scintigrams (n = 11). Scintigrams were five times more expensive than breath tests. CONCLUSIONS: A peaking hydrogen breath test provides an alternative to scintigraphy for estimating intestinal transit after ileoanal pouch.     

Influence of Previously Ingested Wheat on Fasting Breath Hydrogen in Celiac Patients

The excretion of hydrogen in breath commonly persists, despite an overnight fast. Although the elevation of hydrogen concentration above the fasting value after the administration of a test sugar is evidence of malabsorption, the level of the fasting value itself in untreated celiac patients is unknown. Therefore, we studied the fasting breath hydrogen (FBH₂) concentration in 40 healthy controls, 35 subjects with functional bowel disorders, and 30 patients of untreated celiac disease with and without bread or wheat diet one day before the test. The fasting level of hydrogen concentration in untreated celiac patients (28.7 ± 19.5 ppm) was significantly higher than those in healthy volunteers (9.5 ± 3.4 ppm) and subjects with functional bowel disorders (10.6 ± 4.5 ppm). The percentage of patients with elevated H₂ fasting levels in untreated celiac disease (82.5%) was significantly higher than that in healthy controls (10%) and subjects with functional bowel disorders (17.1%). In 30 celiac patients, studied with and without wheat-free diet one day before the test, the fasting hydrogen levels decreased from 28.7 ± 19.5 ppm to 10.6 ± 3.5 ppm, and becoming normal in all patients of celiac disease. Our results show that the patients of untreated celiac disease should be instructed not to eat things made up of wheat one day before hydrogen breath testing so that the normal fasting hydrogen concentration can be obtained and false-negative hydrogen breath test results can be avoided.     

The value of the hydrogen (H2) breath test for the diagnosis of bacterial overgrowth in gastric achlorhydria

Sixteen healthy volunteers, 23 patients with peptic disease, and 38 patients with achlorhydria were investigated with bacterial cultures from gastric juice and a hydrogen (H2) breath test after a standard meal. In acid-secreting subjects upper respiratory tract bacteria were found in 6/39. In every single achlorhydric patient gastric bacterial concentrations were above log 10 5.7/ml. Fecal flora was found in 22/38. The patient with fecal organisms were significantly older than those without (p less than 0.05). The H2 breath test revealed low postprandial carbohydrate fermentation in acid secretors and in achlorhydrics with no fecal flora. The lowest H2 production was found 90 and 120 min after the meal. In achlorhydrics with fecal organisms the mean H2 concentration at these times of measurement was elevated (p less than 0.05). Assuming that a mean H2 concentration at 90 and 120 min above 19 ppm (mean in healthy volunteers at 90 and 120 min + 2 SD) is pathological, the association of fecal bacteria in gastric juice and a "positive" H2 breath test is highly significant (P less than 0.001). Fecal bacteria in the gastric juice would indicate small-intestinal fermentation with a probability of 81%. A gastric culture negative for fecal organisms would predict a "negative" H2 breath test with a probability of 91%.     

Electromyographic analysis of the motility of the right and transverse colon in 9 colostomized patients

The aim of this work was to study the electric pattern of proximal colonic motility in patients with permanent colostomy but without past history of an irritable bowel syndrome. Nine patients (55 to 70 years-old) were investigated using a colonoscope with 5 annular electrodes. An electromyogram was recorded during 4 h. In 5 patients, the results observed before and after a standard test meal were compared. The two usual types of electric activity (i. e. Long Spike Bursts (LSB) and Short Spike Bursts (SSB)) were recorded in the right and transverse colon. The duration of LSB and SSB activities were 8.3 +/- 5.5 and 3.7 +/- 3.5 p. 100 respectively (m +/- SD). In 6 patients, the right and transverse colons were recorded simultaneously; in these patients there was a significant difference in LSB activity between the ascending colon and the transverse colon (10.6 +/- 3.7 and 5.6 +/- 4.3 p. 100 respectively; p less than 0.01). After a meal, the right colonic LSB activity increased (greater than 30 p. 100 of the basal level) in 4 out of 5 patients whereas the transverse colonic LSB activity increased only in one patient. The most striking finding of this study was that colonic hypomotility was of a propulsive and tonic nature. These results could explain the nearly continuous flow of faeces commonly observed in patients with colostomy.     

Lactose malabsorption, irritable bowel syndrome and self-reported milk intolerance

BACKGROUND: The relationship between lactose malabsorption, irritable bowel syndrome and development of intestinal symptoms is unclear, especially when the ingested dose of milk is small. Thus, the role of hydrogen breath testing in the diagnostic work-up of patients with nonspecific intestinal symptoms is still debated. AIMS: To establish the relationship between lactose malabsorption, severe self-reported milk intolerance, irritable bowel syndrome and related symptoms. METHODS: The prevalence of lactose malabsorption was prospectively assessed by means of a hydrogen breath test in 839 patients (503 with irritable bowel syndrome, based on the Rome criteria, regularly consuming milk, and 336 subjects who identified themself as milk intolerant, after an oral load of 25 g lactose). The test was considered "positive" when a hydrogen peak exceeding 20 ppm over baseline values was observed in two or more samples. Attempts were also made to establish whether the predominant presenting symptom (diarrhoea, constipation, alternating diarrhoea and constipation, pain and gaseousness) might be helpful in predicting the outcome of the breath test. RESULTS: The prevalence of a positive breath test was comparable in the two groups (337 patients with irritable bowel syndrome (66.9%) vs 240 patients with milk intolerance (71.4%)). The same holds true for the first peak of hydrogen excretion, total hydrogen output and prevalence of symptoms during, and in the four hours after, the test. The predominant presenting symptom was not useful for predicting outcome of the test either in regular milk users or in milk intolerant subjects. CONCLUSIONS: The almost identical results of the lactose breath test of patients with irritable bowel syndrome and subjects with self-reported milk intolerance suggests that the two conditions overlap to such an extent that the clinical approach should be the same. A lactose breath test should always be included in the diagnostic work-up for irritable bowel syndrome, as fermentation of malabsorbed lactose is likely responsible for triggering symptoms. Conversely, lactase deficiency is probably irrelevant in most subjects not affected by irritable bowel syndrome, within a moderate milk consumption.     

Effect of Dietary Turmeric on Breath Hydrogen

Turmeric is widely used in Indian cuisine. The main constituents of turmeric are curcumin and its analogues, which are well-known antioxidant compounds. In the present study, we hypothesized that turmeric in curry might increase bowel motility and activate hydrogen-producing bacterial flora in the colon, thereby increasing the concentration of breath hydrogen. Eight healthy subjects fasted for 12 h and ingested curry and rice with or without turmeric (turmeric knockout curry). Breath-hydrogen concentrations were analyzed every 15 min for 6 h by gas chromatography with a semiconductor detector. Curry with turmeric significantly increased the area under the curve of breath hydrogen and shortened small-bowel transit time, compared with curry not containing turmeric. These results suggested that dietary turmeric activated bowel motility and carbohydrate colonic fermentation.     

Epidemiology of small bowel bacterial overgrowth and rice carbohydrate malabsorption in Burmese (Myanmar) village children.

Breath hydrogen tests were performed after a rice meal (3 g of cooked rice/kg of body weight, equivalent to 1 g of carbohydrate/kg of body weight) on 256 village children (age range 1-59 months) who were known hydrogen (H2) producers. Anthropometric measurements were made every three months and growth rates were calculated. A breath H2 excretion pattern that suggested small bowel bacterial overgrowth (SBBO), which was recognized as a transient maximum level of 10 ppm or more at 20-, 40-, or 60-min breath samples following the rice meal, was present in 53 (20.7%) children, and was more frequent in children 36-47 and 48-59 months old. This breath H2 excretion pattern was detected in 48 (33.3%) of 144 children who were rice malabsorbers (greater than 10 ppm H2 above baseline values in one of the breath samples taken between 90 and 240 min), and in only five (4.5%) of 112 rice absorbers. Children who had SBBO had a high relative risk (10.7) of being rice malabsorbers. Rice malabsorbers have a high relative risk (59.7) of having faltered growth, accompanied by a large etiologic fraction (94%). This same risk (6.68) and an etiologic fraction of 62% exist in children with untreated SBBO. These findings emphasize the need for interventions aimed at reducing the prevalence of SBBO or similar conditions as detected by the breath H2 excretion pattern to prevent rice malabsorption and growth faltering.     

Short chain fatty acids in human large intestine, portal, hepatic and venous blood.

Evidence for the occurrence of microbial breakdown of carbohydrate in the human colon has been sought by measuring short chain fatty acid (SCFA) concentrations in the contents of all regions of the large intestine and in portal, hepatic and peripheral venous blood obtained at autopsy of sudden death victims within four hours of death. Total SCFA concentration (mmol/kg) was low in the terminal ileum at 13 +/- 6 but high in all regions of the colon ranging from 131 +/- 9 in the caecum to 80 +/- 11 in the descending colon. The presence of branched chain fatty acids was also noted. A significant trend from high to low concentrations was found on passing distally from caecum to descending colon. pH also changed with region from 5.6 +/- 0.2 in the caecum to 6.6 +/- 0.1 in the descending colon. pH and SCFA concentrations were inversely related. Total SCFA (mumol/l) in blood was, portal 375 +/- 70, hepatic 148 +/- 42 and peripheral 79 +/- 22. In all samples acetate was the principal anion but molar ratios of the three principal SCFA changed on going from colonic contents to portal blood to hepatic vein indicating greater uptake of butyrate by the colonic epithelium and propionate by the liver. These data indicate that substantial carbohydrate, and possibly protein, fermentation is occurring in the human large intestine, principally in the caecum and ascending colon and that the large bowel may have a greater role to play in digestion than has previously been ascribed to it.     

Super-efficient starch absorption

We tested the hypothesis that super-efficient starch absorption, by reducing the supply of carbohydrate to the colon, may be associated with and possibly promote colonic neoplasia. By means of breath hydrogen measurements following a potato meal and comparison with the hydrogen response to lactulose, the amount of starch escaping small bowel absorption was measured in 10 patients who had a colonic adenoma removed endoscopically and in 10 controls. The subjects' consumption of starch and fiber was assessed. Percentage unabsorbed starch was approximately half as much in the patients (5.3%) compared with the controls (10.9%, P less than 0.05). Consumption of starch and dietary fiber, and mouth-to-cecum transit times were not significantly different. Unabsorbed starch was calculated to contribute to 6.0 g/day colonic carbohydrate in the patients and 10.9 g/day in the controls (P less than 0.05). This study confirms that unabsorbed starch provides an important quantity of colonic carbohydrate and suggests that super-efficient starch absorption, by reducing this provision, may promote colonic neoplasia.     

Intestinal Gas Production from Bacterial Fermentation of Undigested Carbohydrate in Irritable Bowel Syndrome

The relationship between abdominal pain and bowel gas from bacterial fermentation of undigested carbohydrate was investigated in nine patients with irritable bowel syndrome (IBS), six lactose malabsorbers, and 11 asymptomatic controls. All subjects took breath samples and marked analog scales for abdominal pain, bloating, and psychological stress hourly during all waking hours for 7 days. Breath samples were analyzed for hydrogen concentration within 3 days, and the concentration was corrected for storage time. Symptoms of pain and bloating were significantly more common in IBS patients than in lactose malabsorbers or normal controls, and pain was significantly correlated with bloating in IBS patients. Breath hydrogen concentration was similar in all three groups, and breath hydrogen was not correlated with pain ratings in IBS patients. Thus, abdominal pain may be related to bloating from gastrointestinal gas, but bacterial fermentation cannot be the cause of such gas. The most likely source is swallowed air. This study also demonstrates the feasibility of monitoring hydrogen production in the bowel in field studies by having subjects collect hourly breath samples.