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.     

Breath hydrogen excretion after lactose and whole milk ingestion. A prospective comparison in lactase deficiency

As the 50 g of lactose in the usual clinical test is unphysiologic both because it is equivalent to 1 L milk and because the usual dietary intake is not the purified sugar, but milk, we undertook a prospective comparison of the absorption of lactose after both lactose and milk ingestion with an equivalent lactose content. We studied 51 healthy volunteers, using the hydrogen breath test technique. All patients received 25 g lactose in aqueous solution. Subjects with an abnormal test had the test repeated with 500 ml whole cow's milk, whereas subjects with a normal test repeated the test after ingesting the unabsorbable sugar lactulose to detect the capacity of their colonic flora to produce the gas. Symptoms of gastrointestinal intolerance were also recorded. Compared to an equivalent lactose amount, milk lactose is better absorbed (8% of the entire population malabsorbed 500 ml whole milk, whereas 33.33% malabsorbed 25 g lactose) and induces intolerance in fewer subjects. We conclude that milk rather than pure lactose must be used in clinical evaluation of lactose malabsorption and intolerance.     

Lactose intolerance in active Crohn's disease: clinical value of duodenal lactase analysis.

BACKGROUND: Patients with active Crohn's disease (CD) often report having abdominal symptoms after ingestion of milk products, but the pathomechanism for lactose malabsorption seems to be complex. GOALS: To investigate the prevalence of clinical milk intolerance and to objectify symptoms with hydrogen (H 2 ) breath testing, analysis of lactase protein, and enzyme activity in the duodenal mucosa in patients with CD and in healthy controls. STUDY: In 49 patients with CD and 24 controls, H 2 breath testing was performed. All individuals underwent endoscopy of the upper gastrointestinal tract, in which multiple pinch samples were taken from the distal duodenum. Lactase activity was measured using the method of Dahlquist. The lactase protein expression was analyzed by gel electrophoresis using the monoclonal antibody mlac 10 and by immunochemistry using the monoclonal antibody mlac 4. RESULTS: Prevalence of milk intolerance in healthy controls was 16.6% versus 46.9% in patients with CD, with a high frequency (83.3%) in patients with active disease (CD activity index >150). Milk intolerance was correlated to the duration of inflammatory bowel disease ( p = 0.023) but not to the location or previous bowel resection. Hydrogen breath testing had a moderate sensitivity in detecting lactose maldigestion (70.4%) and a high specificity (95.6%). Duodenal lactase levels were also correlated to disease activity, whereas correlations to clinical symptoms remained poor. Patients with milk intolerance had a significantly reduced bone density at the lumbar spine (z-score, -1.33 +/- 0.92 vs. -0.19 +/- 0.95 [mean +/- SD]; p = 0.002) CONCLUSIONS: Milk intolerance is a frequent problem in active CD, which can be objectified accurately by H 2 lactose breath testing. Decreased lactase levels in the duodenal mucosa may be found during an acute flare but are not the predominant cause of milk intolerance in CD.     

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.     

Lactose intolerance in patients with irritable bowel syndrome from northern India: a case-control study

BACKGROUND AND AIM: Symptoms of irritable bowel syndrome (IBS) and lactose intolerance (LI) overlap. Data on the frequency of LI in patients with IBS from India are scanty. The aim of this study was to evaluate: (i) the frequency of LI in patients with IBS and its various subtypes as compared with healthy subjects (HS) from northern India; (ii) the relationship between self-reported milk intolerance and laboratory evidence of LI; and (iii) the role of small intestinal bacterial overgrowth in LI in patients with IBS. METHODS: 124 patients with IBS (Rome II criteria) and 53 age- and gender-matched HS were studied for LI using the lactose hydrogen breath test (LHBT) and the lactose tolerance test (LTT). Symptoms following lactose ingestion (diarrhea, bloating or distension) during the test and history of milk intolerance were recorded. Sixty-nine of the patients with IBS also underwent a glucose hydrogen breath test (GHBT). Patients with IBS were classified into those with diarrhea (IBS-D; >3 loose stools/d), constipation predominant (IBS-C; <3 stools/week) and indeterminate (IBS-I; between >or=3/week and 相似文献   

Lactase deficiency in Singapore-born and Canadian-born Chinese

Seventy-three of 77 adult Singapore-born Chinese (95%) and 48 of 49 Canadian-born adult Chinese (98%) were demonstrated to be lactase deficient using the lactose breath hydrogen test. The similar prevalence of lactase deficiency in the Singapore- and the Canadian-born Chinese despite a larger estimated amount of daily milk ingestion in the Canadian-born Chinese (430 ml vs 157 ml) supports the concept that lactase deficiency, which is transmitted genetically, does not have an adaptable component related to the quantity of lactose ingested. When the lactose breath hydrogen test performed with a dose of 0.5 g/kg of lactose was compared with the test using a standard dose of 50 g of lactose, there was very little loss of sensitivity. In spite of the presence of lactase deficiency, only 32% of the Singapore subjects and 23% of the Canadian subjects had gastrointestinal symptoms when milk was ingested in the daily diet. Peak breath H₂ was higher in females than males, but the difference was more significant in the Canadian cohort.     

Lactose malabsorption and intolerance in the elderly.

BACKGROUND: Lactase activity declines with age in rats, but it is not clear whether this model is also shared by humans. Few studies have evaluated lactose intolerance and malabsorption in the elderly and no definite conclusions can be drawn. The aim of our study was therefore to verify the impact of age on lactose intolerance and malabsorption. METHODS: Eighty-four healthy subjects took part in the study. Thirty-three were <65 years, 17 were between 65 and 74 years and 34 were >74 years. All the subjects underwent a preliminary evaluation of intestinal gas production capacity and oro-cecal transit time by H2/CH4 breath test after lactulose. After a 3-day period, an H2/CH4 breath test after lactose was performed. The occurrence of intolerance symptoms during the test and in the 24 h after the test was recorded. RESULTS: Breath H2 and CH4 excretion parameters at fasting and after lactulose did not differ between the three groups. Cumulative breath H2 excretion after lactose was higher in subjects >74 years than in subjects <65 years and in subjects aged 65-74 years, while no difference was found between the latter two groups. In subjects >74 years, the prevalence of lactose malabsorption was higher than in the other two groups, while no significant difference was observed between subjects <65 years and subjects aged 65-74 years. Within the malabsorber subjects, the prevalence of lactose intolerance was higher in subjects <65 years than in those aged 65-74 years and in those aged >74 years. No significant difference was found between the latter two groups. No difference was found between the three groups in terms of daily calcium intake and a significant negative correlation between symptom score and daily calcium intake was only found in the group of subjects aged <65 years. CONCLUSIONS: As age increases, the prevalence of lactose malabsorption shows an increase while the prevalence of intolerance symptoms among malabsorbers shows a decrease. Accordingly, daily calcium intake was similar among the adults and elderly studied.     

Lactose Malabsorption and Intolerance in the Elderly

Background: Lactase activity declines with age in rats, but it is not clear whether this model is also shared by humans. Few studies have evaluated lactose intolerance and malabsorption in the elderly and no definite conclusions can be drawn. The aim of our study was therefore to verify the impact of age on lactose intolerance and malabsorption. Methods: Eighty-four healthy subjects took part in the study. Thirty-three were < 65 years, 17 were between 65 and 74 years and 34 were > 74 years. All the subjects underwent a preliminary evaluation of intestinal gas production capacity and oro-cecal transit time by H 2 /CH 4 breath test after lactulose. After a 3-day period, an H 2 /CH 4 breath test after lactose was performed. The occurrence of intolerance symptoms during the test and in the 24 h after the test was recorded. Results: Breath H 2 and CH 4 excretion parameters at fasting and after lactulose did not differ between the three groups. Cumulative breath H 2 excretion after lactose was higher in subjects > 74 years than in subjects < 65 years and in subjects aged 65-74 years, while no difference was found between the latter two groups. In subjects > 74 years, the prevalence of lactose malabsorption was higher than in the other two groups, while no significant difference was observed between subjects < 65 years and subjects aged 65-74 years. Within the malabsorber subjects, the prevalence of lactose intolerance was higher in subjects < 65 years than in those aged 65-74 years and in those aged > 74 years. No significant difference was found between the latter two groups. No difference was found between the three groups in terms of daily calcium intake and a significant negative correlation between symptom score and daily calcium intake was only found in the group of subjects aged < 65 years. Conclusions: As age increases, the prevalence of lactose malabsorption shows an increase while the prevalence of intolerance symptoms among malabsorbers shows a decrease. Accordingly, daily calcium intake was similar among the adults and elderly studied.     

Breath testing to evaluate lactose intolerance in irritable bowel syndrome correlates with lactulose testing and may not reflect true lactose malabsorption

OBJECTIVES: An increased prevalence of lactose intolerance is seen in irritable bowel syndrome (IBS). Recently, we demonstrated a high prevalence of abnormal lactulose breath test results in IBS suggesting bacterial overgrowth. Because symptoms of lactose intolerance result from bacterial fermentation, the purpose of this study was to determine whether an abnormal lactose breath test is reflective of malabsorption or early presentation to bacteria. METHODS: Subjects with diarrhea-predominant IBS were enrolled. On day 1, subjects underwent a lactulose breath test after an overnight fast. Within 1 wk, subjects returned after fasting for a lactose breath test with simultaneous blood glucose measurements every 15 min to complete a lactose tolerance test (LTT). Symptoms were evaluated 3 h after lactose administration. RESULTS: Twenty subjects completed the study. One subject inadvertently received dextrose through the intravenous and was excluded. Of the remaining 19 subjects, three (16%) had an abnormal LTT suggesting malabsorption. In all, 10 subjects (53%) had an abnormal lactose breath test, 14 (74%) had an abnormal lactulose breath test, and 11 (58%) had symptoms after lactose administration. The agreement with symptoms was moderate (kappa = 0.47) and fair (kappa = 0.24) when compared to the lactose breath test and LTT, respectively. There was a fair correlation between lactose breath test and LTT (kappa = 0.29). However, lactose breath test hydrogen levels >166 ppm were universally predictive of abnormal LTT. Finally, a significant correlation was seen between the hydrogen production on lactose and lactulose breath test (r = 0.56, p = 0.01). CONCLUSIONS: Lactose breath testing in IBS subjects does not seem to reflect malabsorption; it may be an indicator of abnormal lactulose breath test, suggesting bacterial overgrowth.     

Efficacy of Addition of Exogenous Lactase to Milk in Adult Lactase Deficiency

The efficacy of lactase by Kluyveromyces lactis in hydrolyzing milk lactose and reducing milk intolerance symptoms was tested in 52 proved lactose malabsorbers. The enzyme was added to milk administered to the patients, and H2 breath excretion (as an index of carbohydrate malabsorption), was determined by gas chromatograph technique, and milk intolerance symptoms were recorded. H2 mean excretion was 78.3 +/- 5.49 ppm after administration of intact whole milk 500 ml (test A), 43.5 +/- 4.99 ppm when lactase 2000 U was added to milk 500 ml immediately before administration (test B); 36.7 +/- 5.01 ppm when milk 500 ml was incubated for 12 h with lactase 1000 U (test C), and 29.7 +/- 4.35 ppm when the incubation was prolonged for 24 h (test D). Symptoms score was: test A = 5.85 +/- 0.56, test B = 3.71 +/- 0.45, test C = 2.77 +/- 0.63, test D = 1.7 +/- 0.68. A correlation index of r = 0.44 (p less than 0.01) was obtained between reduction in H2 mean excretion and reduction in symptoms score of a single individual. The addition of this lactase to milk seems to be effective in correcting lactose malabsorption, thus representing a convenient approach in milk intolerance.     

Enzyme replacement therapy for primary adult lactase deficiency. Effective reduction of lactose malabsorption and milk intolerance by direct addition of beta-galactosidase to milk at mealtime

The addition of microbial beta-galactosidases directly to milk at mealtime represents a potential "enzyme replacement therapy" for primary lactase deficiency. We used the hydrogen breath test as the index of incomplete carbohydrate absorption to assess the efficacy of two enzymes--one from yeast, Kluyveromyces lactis (LactAid), and the other from the fungus Aspergillus niger (Lactase N)--to assist in the hydrolysis of 18 g of lactose in 360 ml (12 oz) of whole milk when consumed by an adult lactose malabsorber. Graded amounts of Lactase N produced, at best, a 53% relative reduction in breath hydrogen excretion, whereas quantitative elimination of excess hydrogen excretion was produced by 1 and 1.5 g of LactAid. A double-blind, controlled, crossover trial was subsequently performed in 50 healthy, unselected Mexican adults, to whom 360 ml of cow's milk was presented in the three forms in a randomized order: intact milk, prehydrolyzed milk, and milk to which 1 g of LactAid was added immediately before consumption. Among the 25 subjects with incomplete carbohydrate absorption with intact milk, adding enzyme 5-min before consumption produced a 62% reduction in breath hydrogen excretion, and symptoms of intolerance were significantly reduced. The feasibility of effective enzyme replacement therapy with a beta-galactosidase from K. lactis is demonstrated.     

High prevalence of celiac disease in patients with lactose intolerance

BACKGROUND/AIMS: Acquired lactase deficiency is a common cause of gastrointestinal symptoms but its etiology remains unclear. Celiac disease could lead to lactase deficiency and is much more common than previously suspected. Several studies have highlighted the prevalence of lactose intolerance in celiac disease, but studies assessing the prevalence of celiac disease in lactose intolerance are lacking. We evaluated the prevalence of celiac disease in patients with a positive H2-lactose breath test compared to a control group. METHODS: This retrospective study included 54 patients (15 males/39 females; mean age 37.8 +/- 7 years) from southern Italy, referred to the Gastroenterology Unit for bloating and diarrhea after the introduction of milk or dietary lactose. They had a positive H2-lactose breath test and a negative H2-glucose breath test. 50 blood donors were drawn from a similar population, matched for sex and age, and enrolled as a control group. All patients were screened for possible celiac disease by measuring the serum level of IgA antibodies to endomysium, anti-transglutaminase and total IgA. Patients positive for at least one of these markers were submitted to upper gastrointestinal endoscopy. RESULTS: None of the patients had a IgA deficiency. 24% of the patients showed positivity of celiac disease antibodies compared to 2% in the control group (p < 0.001). Histologic samples of these patients showed villous atrophy (53.8% Marsh type IIIa, 38.4% Marsh IIIb, and 7.6% with Marsh type IIIc) confirming the celiac disease, while in the control subjects duodenal biopsies were normal. CONCLUSIONS: A high prevalence of celiac disease was observed in patients with a positive H2-lactose breath test compared to healthy controls. In these subjects lactase deficiency seems to be the only manifestation of celiac disease. We suggest serologic screening for celiac disease in all patients with a positive H2-lactose breath test before beginning a milk-exclusion diet.     

Respiratory methane excretion in children with lactose intolerance

Two evaluate the relationship between colonic methane production and carbohydrate malabsorption, we measured end-expiratory methane levels in 70 normal and 40 lactose-intolerant children. Time-dependent excretion of hydrogen and methane was determined every 30 min for 120 min following a fasting oral lactose challenge (2 g/kg). Mean breath hydrogen levels in normals (lactose-tolerant) equaled 3.7 parts per million (ppm) throughout the study, but increased to >10 ppm by 60 min and remained elevated in lactose-intolerant subjects. Breath methane in normal children averaged 1.6 ppm from 0 to 120 min. In contrast, CH₄ excretion by lactose-intolerant children averaged 5.1 ppm at 90 min; and, by 120 min levels increased significantly compared with control. Breath methane levels in lactose-intolerant subjects following a lactose load continued to increase, however, despite the coingestion of exogenous lactase in amounts calculated to result in complete hydrolysis of the disaccharide. These data demonstrate that lactase-deficient children manifest significant increases in breath methane excretion following lactose ingestion and that enhanced methane production may be a consequence of several factors, including altered fecal pH and increased methanogenic substrates provided by colonic lactose fermentation. Further studies are required to determine the clinical significance of elevated methane production in lactose intolerance.     

Effect of Guar, Pectin, Psyllium, Soy Polysaccharide, and Cellulose on Breath Hydrogen and Methane in Healthy Subjects

Different types of dietary fiber are fermented to various extents in vitro, but little is known about the effects of fiber on breath hydrogen and methane levels in vivo. Therefore, we studied the effects on breath hydrogen and methane of 15 g of guar, pectin, psyllium, soy polysaccharide, or cellulose in eight healthy subjects over a 12-h period. None of the fibers had a significant effect on breath hydrogen or methane concentrations, compared with the control (fasting). The four methane producers had lower breath hydrogen levels than the nonproducers 1 h after 15 g of lactulose (3 +/- 1 vs. 42 +/- 9, p less than 0.005) and 5-12 h after the different fibers (3.3 vs. 4.8 ppm; pooled SEM = 0.8; p less than 0.025). When the methane responses of the methane producers were expressed as increments relative to the control, there were small differences between treatments, with guar producing a larger response, 8.2 +/- 3.3 ppm, than cellulose, -2.9 +/- 2.3 ppm (p less than 0.05). The incremental methane responses of the different fibers in vivo were related to the previously reported production of propionic acid (r = 0.94, n = 5, p less than 0.02) and methane (r = 0.93, n = 4, NS) from in vitro fermentation of the same fibers. We conclude that methane producers have lower breath hydrogen levels than nonproducers. Purified fermentable and nonfermentable dietary fibers have no effect on breath hydrogen levels over 12 h in subjects previously consuming a normal diet. However, fermentable fibers may produce small increases in breath methane in methane-producing subjects.     

Starch malabsorption and breath gas excretion in healthy humans consuming low- and high-starch diets

Dietary starch delivery to the colon and excretion in stools and the ability of unabsorbed carbohydrates to promote hydrogen and methane release in breath were evaluated in 6 volunteers during two 8-day periods on starch diets of 100 and 300 g, respectively. Significantly less starch was recovered from the terminal ileum by aspiration per 24 h during the low-starch period (4.1 +/- 0.3 vs. 9.5 +/- 1.1 g, mean +/- SEM, p less than 0.01). Unabsorbed glucose tended to rise during the high-starch period (2.7 +/- 0.8 vs. 1.1 +/- 0.3 g). Fecal outputs of starch, glucose, volatile fatty acids, and lactic acid were not significantly different during the two periods. Daily breath hydrogen excretion was unchanged (181.2 +/- 22.7 vs. 193.7 +/- 19.8 ml for the low- and high-starch periods, respectively), whereas breath methane excretion increased markedly in the three methane producers during the high-starch period (217.2 +/- 80.9 vs. 32.4 +/- 7.3 ml). Starch malabsorption in the healthy small intestine was moderate even with a high-starch diet and less than that previously estimated by indirect methods. Unabsorbed starch catabolism by the colonic flora does not seem to explain most of the breath hydrogen excretion.     

Concordance of indirect methods for the detection of lactose malabsorption in diabetic and nondiabetic subjects

In order to collect data on (1) the prevalence of lactose malabsorption and (2) the value of indirect diagnostic methods for hypolactasia in diabetics, we compared lactose tolerance tests using serum glucose, serum galactose (after oral ethanol intake) and breath hydrogen excretion as diagnostic cutoff in 144 nondiabetic and 46 diabetic subjects. A good rate of concordance was found for the hydrogen breath test and galactose-dependent lactose tolerance test. The glucose-dependent lactose tolerance test was found to be of satisfactory diagnostic value in nondiabetic subjects and was useless for diagnostic purposes in diabetics. Lactose malabsorption was no more frequent in diabetics than in controls and lactose intolerance was found to be less frequent in the diabetic group. A distinction between hypolactasia and other gastrointestinal disorders in diabetics is possible by ambulatory indirect tests.     

Assessment of lactose absorption by measurement of urinary galactose

Individuals with sufficient intestinal lactase hydrolyze ingested lactose to galactose and glucose and these monosaccharides are absorbed. Lactose is not digested completely when intestinal lactase activity is low and the disaccharide is malabsorbed. Breath hydrogen excretion after lactose ingestion is used commonly to diagnose lactose malabsorption. However, no direct tests are currently used to assess lactose absorption. We tested a new method of assessing lactose absorption in 26 healthy individuals. Each subject ingested 50 g of lactose. Participants were evaluated for lactose malabsorption using a standard 3-h breath hydrogen test. In addition, the urinary excretions of galactose, lactose, and creatinine were quantitated for 3-5 h after lactose ingestion. On the basis of breath hydrogen analysis after lactose ingestion, 12 individuals were lactose malabsorbers (defined as a rise in the breath hydrogen concentration of greater than 20 parts per million above the baseline value). The 14 subjects who did not malabsorb lactose by breath hydrogen testing (defined as a rise in the breath hydrogen concentration of less than or equal to 20 parts per million above the baseline value), had significantly more galactose in their urine 1, 2, and 3 h after lactose ingestion than lactose malabsorbers. The ratio of excreted lactose to excreted galactose was significantly decreased in lactose absorbers compared with lactose malabsorbers (p less than 0.001). Determination of the ratio of urinary galactose to urinary creatinine separated lactose absorbers from lactose malabsorbers completely (p less than 0.001). We conclude from this study that the determination of urinary galactose, urinary lactose/galactose ratio, and urinary galactose/creatinine ratio may be used to assess lactose digestion and absorption in healthy adults.     

Evidence for Colonic Conservation of Malabsorbed Carbohydrate in Short Bowel Syndrome

The purpose of this study was to determine whether energy from malabsorbed carbohydrate could be conserved through colonic fermentation in short bowel syndrome. Seven patients with short bowel anastomosed to the remaining colon and five patients with short bowel without a colon were selected from the home total parenteral nutrition (TPN) program. Six normal volunteers also were studied. After an overnight fast, subjects consumed a 50-g carbohydrate bread meal and were studied hourly over the next 6 h. Carbohydrate malabsorption, estimated by lactulose breath hydrogen testing, was 48 +/- 13% in short bowel patients. After the bread meal, breath hydrogen was higher in short bowels with colons (69 +/- 20 ppm) than in either short bowels without colons (11 +/- 7 ppm) or normal subjects (10 +/- 3 ppm) (p less than 0.01). Blood acetate levels also were higher in short bowels with colons than in those without colons, reaching a peak of 167 +/- 27 mumol/L at 4 h (p less than 0.05). We conclude that in patients with a short bowel and a colon, malabsorbed carbohydrate is fermented and there is a rise in blood acetate, suggesting that the colon has a role in salvaging malabsorbed carbohydrate as a source of energy through carbohydrate fermentation.     

Lactase deficiency: a common genetic trait of the American Indian

Intestinal lactase activity was assessed indirectly in 156 American Indians by measuring breath hydrogen after an oral lactose load. Lactase deficiency was present in 66% of subjects and correlated highly with the percentage of Indian blood. Lactase deficiency was present by the age of 5 years and was unrelated to sex. Most lactase-deficient subjects (81%), but only a minority (23%) of lactase-sufficient subjects, developed symptoms after the oral lactose load, and among lactase-deficient subjects, symptoms occurred more frequently in adults than in children (P = 0.05). Indeed, by history, 53% of lactase-deficient adults, but only 10% of lactase-deficient children under 18 years of age, were aware of milk intolerance. Despite these differences, milk consumption was only slightly less (19 g) in the lactase-deficient subjects than in those with normal lactase activity (25 g) (P less than 0.05). The results indicate that lactase deficiency is a common autosomal genetic trait in the American Indian that becomes manifest in early childhood. Tolerance to dietary lactose appears to decline in the American Indian as he reaches adulthood, but in this population the decline in tolerance had only minor influence on lactose intake.