The Role of Colonic Microbiota in Lactose Intolerance

In a previous study we observed a clear difference in lactose intolerance symptoms after a 25-g lactose load in two groups of persons with lactase nonpersistence and similar small intestinal lactase activity. From this observation we hypothesized a colon resistance factor. To identify this factor, the microbial composition of fecal samples of the two lactose intolerant groups (one with mild symptoms, n = 16, and one with diarrhea-predominant symptoms, n = 11) was compared using the fluorescent in situ hybridization technique. Large interindividual differences were found in the numbers of total bacteria and main groups of bacteria (CV: 0.65 and 0.64-0.82 respectively). The bacterial numbers were not significantly different between the two groups. A significant negative correlation, however, was found between the individual symptom scores of the intolerant persons and the numbers of total hybridizable bacteria (r(s) = -0.42, P = 0.03). The results suggest that an increased number of bacteria might contribute--by means of a higher fermentative capacity--to the reduction of lactose intolerance symptoms.     

Rifaximin in patients with lactose intolerance

BACKGROUND: Abdominal symptoms linked to lactose malabsorption may be caused by metabolic activity of colonic bacteria. Rifaximin, a non-absorbable rifampycin derivative, is active against colonic bacteria, it may be useful in the treatment of lactose intolerance. AIM: The aim of this study has been to evaluate short-term rifaximin therapy in patients with lactose intolerance. METHODS: Thirty-two patients with lactose intolerance diagnosed using the hydrogen lactose breath test were studied. Fourteen patients received rifaximin 800 mg/day for 10 days, 13 patients followed a diet without milk for 40 days and 5 patients received a placebo for 10 days. Total breath H(2) excretion expressed as area under the curve, and the symptom score were evaluated in all patients at the start, and subsequently after 10 and 40 days. RESULTS: In the 14 patients who received rifaximin for 10 days, area under the curve at day 10 and day 40 was statistically significantly lower than the one computed at basal (P<0.01). Diet reduced area under the curve progressively reaching statistical significance at day 40, while the placebo did not change area under the curve throughout the study. The total symptom score significantly improved after rifaximin and diet. CONCLUSION: In patients with lactose intolerance, a 10-day therapy with rifaximin as well as 40-day diet without lactose reduces the area under the curve and the symptom score.     

Management and treatment of lactose malabsorption

Lactose malabsorption is a very common condition characterized by intestinal lactase deficiency. Primary lactose malabsorption is an inherited deficit present in the majority of the world's population, while secondary hypolactasia can be the consequence of an intestinal disease. The presence of malabsorbed lactose in the colonic lumen causes gastrointestinal symptoms. The condition is known as lactose intolerance. In patients with lactase nonpersistence, treatment should be considered exclusively if intolerance symptoms are present. In the absence of guidelines, the common therapeutic approach tends to exclude milk and dairy products from the diet. However, this strategy may have serious nutritional disadvantages. Several studies have been carried out to find alternative approaches, such as exogenousβ-galactosidase, yogurt and probiotics for their bacterial lactase activity, pharmacological and non pharmacological strategies that can prolong contact time between enzyme and substrate delaying gastrointestinal transit time, and chronic lactose ingestion to enhance colonic adaptation. In this review the usefulness of these approaches is discussed and a therapeutic management with a flow chart is proposed.     

All Lactase Preparations Are Not the Same: Results of a Prospective, Randomized, Placebo-Controlled Trial

Objective: To compare the efficacy of three commercially available oral lactase preparations in adults with lactose intolerance. Methods: Design—Prospective, randomized, placebo-controlled trial. Setting—Outpatient study in a General Clinical Research Center. Subjects—Ten lactose-intolerant healthy volunteers were challenged with ice cream containing 18 g of lactose. Lactase or placebo was given immediately prior to challenge. Measurements—Symptoms and breath hydrogen excretion were recorded for 3 h following lactose challenge. Results: The three products differed in their abilities to influence symptoms and breath hydrogen excretion. Only Lactaid reduced the breath hydrogen excretion with lactose (mean peak, area under the curve and cumulative breath hydrogen excretion) ( P < 0.05). Lactrase and Dairy Ease influenced symptoms: Lactrase reduced pain, bloating and total symptomatic scores ( P < 0.05), whereas Dairy Ease only reduced pain ( P < 0.05). Lactaid administration did not reduce symptoms. Conclusion: In lactose-intolerant subjects, the available lactase preparations differ in their ability to improve both breath hydrogen excretion and symptoms. Lactrase may be the product of choice for achieving symptomatic improvement.     

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.     

乳糖酶缺乏与乳糖不耐受症状的临床特点分析

目的 探讨乳糖酶缺乏及乳糖不耐受症状的临床特点.方法 回顾性分析了84例于广东省人民医院门诊就诊的以腹痛、腹泻、腹胀、肠鸣为主要症状的患者,并接受胃肠镜、腹部CT、抽血及氢呼气试验等检查评估,根据患者的主要诊断,氢呼气试验结果及乳糖不耐受症状进行分组,比较各组的临床指标,包括年龄、性别、体质量指数、血常规、过敏原检测、...     

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.     

Genetic test for lactase non-persistence and hydrogen breath test: Is genotype better than phenotype to diagnose lactose malabsorption?

BackgroundAdult-type hypolactasia is a widespread condition throughout the world, causing lactose malabsorption. The lactose breath test is a simple tool for diagnosis but the need for prolonged monitoring of hydrogen excretion has led to a genetic test proposal. The aim of this study was to compare the genetic test with the lactose breath test in order to give some insights into the clinical value of genetic testing.MethodsThirty-two consecutive functional patients underwent lactose breath test and lactase genetic polymorphism analysis (C/T 13910 and G/A 22018). Intolerance symptoms after lactose load were also monitored.ResultsAll patients with positive lactose breath test showed homozygosis for both polymorphisms. Among the nine patients with a negative breath test result, six showed heterozygosis while three showed homozygosis. Intolerance symptoms were present in 16 homozygotic patients but also in one heterozygotic patient. The k value for the agreement between the genetic test and the lactose breath test was 0.74.ConclusionA positive genetic test for lactase non-persistence indicates whether lactase activity decline may represent a clinical problem for the patient, but does not give information on actual patient symptoms. On the contrary, this information is already available by combining the lactose breath test with intolerance symptom evaluation. Lactose absorption phenotype may be not yet evident until young adult age.     

Adult lactose digestion status and effects on disease

BACKGROUND:

Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes.

OBJECTIVES:

To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions.

METHODS:

A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic.

RESULTS:

The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide.

DISCUSSION:

The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases.

CONCLUSIONS:

Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing.     

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.     

Lactose malabsorption and intolerance: What should be the best clinical management?

Lactose malabsorption (LM) is the incomplete hydrolysis of lactose due to lactase deficiency, which may occur as a primary disorder or secondary to other intestinal diseases. Primary adult-type hypolactasia is an autosomal recessive condition resulting from the physiological decline of lactase activity. Different methods have been used to diagnose LM. Lactose breath test represents the most reliable technique. A recent consensus conference has proposed the more physiological dosage of 25 g of lactose and a standardized procedure for breath testing. Recently a new genetic test, based on C/T13910 polymorphism, has been proposed for the diagnosis of adult-type hypolactasia, complementing the role of breath testing. LM represents a wellknown cause of abdominal symptoms although only some lactose malabsorbers are also intolerants. Diagnosing lactose intolerance is not straightforward. Many non-malabsorber subjects diagnose themselves as being lactose intolerant. Blind lactose challenge studies should be recommended to obtain objective results. Besides several studies indicate that subjects with lactose intolerance can ingest up to 15 g of lactose with no or minor symptoms. Therefore a therapeutic strategy consists of a lactose restricted diet avoiding the nutritional disadvantages of reduced calcium and vitamin intake. Various pharmacological options are also available. Unfortunately there is insufficient evidence that these therapies are effective. Further double-blind studies are needed to demonstrate treatment effectiveness in lactose intolerance.     

Lactose intolerance in Jewish patients with ulcerative colitis

Seventy patients with ulcerative colitis had lactose tolerance tests. Of 51 non-Jewish patients, 12 (23.5%) had lactose intolerance, whereas of 19 Jewish patients, 16 (84.2%) had lactose intolerance. This difference is significant (P<0.001). The control group of 41 Jews without ulcerative colitis had a 71% incidence of lactose intolerance, whereas of 53 non-Jewish controls, only 20.7% had such intolerance. These results are also statistically valid (P<0.001). This suggested that segregation of the genes for ulcerative colitis as well as for lactase deficiency in Jews is a possible reason for the high incidence of lactase deficiency found in patients with ulcerative colitis.Supported by a grant from The Hartford Foundation.     

Four-sample lactose hydrogen breath test for diagnosis of lactose malabsorption in irritable bowel syndrome patients with diarrhea

AIM: To validate 4-sample lactose hydrogen breath testing (4SLHBT) compared to standard 13-sample LHBT in the clinical setting.METHODS: Irritable bowel syndrome patients with diarrhea (IBS-D) and healthy volunteers (HVs) were enrolled and received a 10 g, 20 g, or 40 g dose lactose hydrogen breath test (LHBT) in a randomized, double-blinded, controlled trial. The lactase gene promoter region was sequenced. Breath samples and symptoms were acquired at baseline and every 15 min for 3 h (13 measurements). The detection rates of lactose malabsorption (LM) and lactose intolerance (LI) for a 4SLHBT that acquired four measurements at 0, 90, 120, and 180 min from the same data set were compared with the results of standard LHBT.RESULTS: Sixty IBS-D patients and 60 HVs were studied. The genotype in all participants was C/C-13910. LM and LI detection rates increased with lactose dose from 10 g, 20 g to 40 g in both groups (P < 0.001). 4SLHBT showed excellent diagnostic concordance with standard LHBT (97%-100%, Kappa​​ 0.815-0.942) with high sensitivity (90%-100%) and specificity (100%) at all three lactose doses in both groups.CONCLUSION: Reducing the number of measurements from 13 to 4 samples did not significantly impact on the accuracy of LHBT in health and IBS-D. 4SLHBT is a valid test for assessment of LM and LI in clinical practice.     

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.     

Peppermint oil (Mintoil) in the treatment of irritable bowel syndrome: A prospective double blind placebo-controlled randomized trial

INTRODUCTION: The use of peppermint oil in treating the irritable bowel syndrome has been studied with variable results probably due to the presence of patients affected by small intestinal bacterial overgrowth, lactose intolerance or celiac disease that may have symptoms similar to irritable bowel syndrome. AIM: The aim of the study was to test the effectiveness of enteric-coated peppermint oil in patients with irritable bowel syndrome in whom small intestinal bacterial overgrowth, lactose intolerance and celiac disease were excluded. METHODS: Fifty-seven patients with irritable bowel syndrome according to the Rome II criteria, with normal lactose and lactulose breath tests and negative antibody screening for celiac disease, were treated with peppermint oil (two enteric-coated capsules twice per day or placebo) for 4 weeks in a double blind study. The symptoms were assessed before therapy (T(0)), after the first 4 weeks of therapy (T(4)) and 4 weeks after the end of therapy (T(8)). The symptoms evaluated were: abdominal bloating, abdominal pain or discomfort, diarrhoea, constipation, feeling of incomplete evacuation, pain at defecation, passage of gas or mucus and urgency at defecation. For each symptom intensity and frequency from 0 to 4 were scored. The total irritable bowel syndrome symptoms score was also calculated as the mean value of the sum of the average of the intensity and frequency scores of each symptom. RESULTS: At T(4), 75% of the patients in the peppermint oil group showed a >50% reduction of basal (T(0)) total irritable bowel syndrome symptoms score compared with 38% in the placebo group (P<0.009). With peppermint oil at T(4) and at T(8) compared with T(0) a statistically significant reduction of the total irritable bowel syndrome symptoms score was found (T(0): 2.19+/-0.13, T(4): 1.07+/-0.10*, T(8): 1.60+/-0.10*, *P<0.01 compared with T(0), mean+/-S.E.M.), while no change was found with the placebo. CONCLUSION: A 4 weeks treatment with peppermint oil improves abdominal symptoms in patients with irritable bowel syndrome.     

Differential impact of lactose/lactase phenotype on colonic microflora

BACKGROUND:

The ability to digest lactose divides the world’s population into two phenotypes that may be risk variability markers for several diseases. Prebiotic effects likely favour lactose maldigesters who experience lactose spilling into their colon.

OBJECTIVE:

To evaluate the effects of fixed-dose lactose solutions on fecal bifidobacteria and lactobacilli in digesters and maldigesters, and to determine whether the concept of a difference in ability to digest lactose is supported.

METHODS:

A four-week study was performed in 23 lactose mal-digesters and 18 digesters. Following two weeks of dairy food withdrawal, subjects ingested 25 g of lactose twice a day for two weeks. Stool bifidobacteria and lactobacilli counts pre- and postintervention were measured as the primary outcome. For secondary outcomes, total anaerobes, Enterobacteriaceae, beta-galactosidase and N-acetyl-beta-D-glucosaminidase activity in stool, as well as breath hydrogen and symptoms following lactose challenge tests, were measured.

RESULTS:

Lactose maldigesters had a mean change difference (0.72 log₁₀ colony forming units/g stool; P=0.04) in bifidobacteria counts compared with lactose digesters. Lactobacilli counts were increased, but not significantly. Nevertheless, reduced breath hydrogen after lactose ingestion correlated with lactobacilli (r=−0.5; P<0.001). Reduced total breath hydrogen and symptom scores together, with a rise in fecal enzymes after intervention, were appropriate, but not significant.

CONCLUSIONS:

Despite failure to achieve full colonic adaptation, the present study provided evidence for a differential impact of lactose on microflora depending on genetic lactase status. A prebiotic effect was evident in lactose maldigesters but not in lactose digesters. This may play a role in modifying the mechanisms of certain disease risks related to dairy food consumption between the two phenotypes.     

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 Ulcer Surgery on Disaccharidase Activities of the Small Bowel and on Lactose Absorption

In 14 patients with peptic ulcer, admitted to hospital for surgical treatment, the lactose tolerance test and a small-intestinal biopsy with disaccharidase (maltase, sucrase, lactase) assays were performed before and 1 month and 6 months after operation. In 10 patients without evident organic disease of the gastrointestinum, the small-intestinal biopsy with disaccharidase assays was repeated at an average interval of 1 week, and these form the control group. The mean maltase, sucrase and lactase activities in the 1 and 6-month follow-up studies were increased over the preoperative values. When the changes were compared with the alterations noted in the control group, no statistically significant difference could be noted. In 3 patients with small-intestinal lactase deficiency the symptoms following lactose tolerance test became worse in one and a history of milk intolerance appeared in one after ulcer surgery.     

Lactose intolerance in adults with chronic unspecific abdominal complaints

77 hospitalized patients with chronic unspecific abdominal complaints, in whom any other organic disease had been previously excluded, were investigated for lactose malabsorption; they were subdivided into two groups: 46 patients complaining primarily of colicky abdominal pain and/or intermittent diarrhoea (group 1) and 31 patients presenting with dyspepsia as the predominant symptom (group 2). To establish the exact prevalence of isolated lactase deficiency in the healthy adult population served by our hospital, 40 Italian adult healthy subjects were also studied. The prevalence of lactose malabsorption was significantly higher (p less than 0.005) in patients of the 1st group than in patients of the 2nd group, and in the healthy adult population seen at our hospital (74% vs 35.5% and 37.5%, respectively). Furthermore a high prevalence of lactose intolerance, determined by means of a three-week diet trial (lactose free-diet versus normal diet), was documented among lactose malabsorbers of the 1st group. We concluded therefore that lactose intolerance is a factor in some Italian adult patients who suffer from long-standing aspecific abdominal discomfort, and it should be always considered in these patients, especially when colicky abdominal pain and diarrhoea are present, before the diagnosis of irritable bowel syndrome is made.     

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.