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PubMed1999

Production of low-lactose milk by ectopic expression of intestinal lactase in the mouse mammary gland.

We have investigated, in mice, an in vivo method for producing low-lactose milk, based on the creation of transgenic animals carrying a hybrid gene in which the intestinal lactase-phlorizin hydrolase cDNA was placed under the control of the mammary-specific alpha-lactalbumin promoter. Transgenic females expressed lactase protein and activity during lactation at the apical side of mammary alveolar cells. Active lactase was also secreted into milk, anchored in the outer membrane of fat globules. Lactase synthesis in the mammary gland caused a significant decrease in milk lactose (50-85%) without obvious changes in fat and protein concentrations. Sucklings nourished with low-lactose milk developed normally. Hence, these data validate the use of transgenic animals expressing lactase in the mammary gland to produce low-lactose milk in vivo, and they demonstrate that the secretion of an intestinal digestive enzyme into milk can selectively modify its composition.

Animals↗
PubMed1975

The topography of lactose synthesis.

1. At short incubation times, and under suitable osmotic conditions, the lactose synthesized by Golgi-derived vesicles of rat mammary gland is 85-90% particulate. Evidence is presented for its occlusion within the lumen of the vesicles. 2. Ovalbumin is used as a bulky active-site inhibitor to show that the active site of lactose synthase lies on the inner face of the Golgi membrane. 3. Phlorrhizin and phloretin inhibit lactose synthesis by such vesicles, indicating the presence of a glucose-transport system. 4. The relationship of this topography to the synthesis of N-acetylneuraminyl-lactose and to the secretion of milk sugars is discussed.

Animals↗
PubMed2002

Review article: lactose--a potential prebiotic.

Lactose maldigestion, which affects a large majority of the world's population, has been mostly linked with uncomfortable symptoms. In addition, dairy consumption is variably blamed or recommended for a number of ill effects. There is, however, emerging evidence that certain lactic acid-producing bacteria, which selectively consume prebiotics, may be beneficial against some lower intestinal diseases. Lactose maldigestion and lactose should perhaps be re-evaluated as a potential provider of such a prebiotic. This historical and observational review discusses lactose and argues the opinion that it has prebiotic potential. Moreover, in maldigesters, natural ingestion or lack thereof may be relevant in the pathogenesis of diseases such as colorectal cancer and inflammatory bowel diseases.

Dairy Products↗
PubMedDate not supplied

[Hydrogen (H2) breath test following lactose loading in children with recurrent abdominal pain].

To define the practical diagnostic value of H2 breath testing after lactose load in children with chronic abdominal pain, we measured end-expiratory H2 every 30 minutes for 2 hours after peroral lactose (2 g/kg body weight, Lactoscreen). H2 testing was done in 62 children (28 female, 32 male), aged between 2 and 16 years. Abdominal pain had been observed in these children for more than 2 months. Causes of abdominal pain other than lactose intolerance had been excluded. In 2 out of 62 children, H2 testing was impossible for lack of cooperation. 17 out of the remaining 60 children showed a positive test result (28.3%). In 15 patients, the rise in H2 exceeded 40 ppm, and was thus easily distinguished from a nonspecific rise (less than 25 ppm). Stool pH and Clini-test results were not correlating well with H2 findings, In 16 out of 17 children with positive H2 tests, abdominal pain had ceased on a diet free of lactose after a month. After 6 months 15 out of 17 children were symptom free. These data confirm early indication of non-invasive H2 testing in children with chronic abdominal pain.

Abdominal Pain↗
PubMed2000

Lactose intolerance.

Lactose maldigestion has been under intensive research since its discovery in the 1960's. We know the prevalence of lactose maldigestion in a great number of countries and ethnic groups. However, there is often no provision made for the secondary type of maldigestion, and the study populations have sometimes been selected rather than picked at random. New methods for the measurement of lactose digestion have been developed, and its genetic mechanisms have received a great deal of attention during the last few years. However, in many studies the measurement and/or reporting of symptoms has quite often been overlooked. In this review, various topics related to lactose intolerance are discussed with a special emphasis on its symptoms.

Animals↗
PubMed2002

Use of the lactose H2 breath test to monitor mucosal healing in coeliac disease.

UNLABELLED: Confirmation of the diagnosis of coeliac disease requires unequivocal evidence of recovery on a gluten-free diet. The lactose H2 breath test is a non-invasive technique for detecting lactose malabsorption, and this may occur in untreated coeliac disease. The utility of this test was investigated in objectively confirming a response to gluten exclusion. The study included 44 children from 0.9 to 14.75 y of age (median 3.2) with coeliac disease. Five children were asymptomatic, being identified through coeliac antibody screening. Breath tests were performed prior to dietary treatment. If positive, they were repeated at 4-wk intervals following gluten exclusion. Overall, 21/44 (48%) children had positive breath tests at presentation. In 18/21 children on a gluten-free diet, this became negative after 4 wk (86%) and in all the children by 8 wk. In two children with positive tests at 4 wk, problems with dietary adherence were identified. A positive test before treatment was not associated with significant differences in individual symptoms, height, weight and body mass index standard deviation scores, serum haemoglobin or albumin. However, no positive results were found in the asymptomatic patients (p = 0.05). Lactose malabsorption was associated with earlier age of presentation (p = 0.008). CONCLUSION: The lactose H2 breath test objectively confirms a response to gluten exclusion. In selected cases it can help confirm a diagnosis of coeliac disease. However, the test tends to be less informative in asymptomatic patients, and in older children.

Adolescent↗
PubMed1975

Correlation of lactase activity, lactose tolerance and milk consumption in different age groups.

Small intestinal lactase activity in the health adult is either the same as in early infancy or may drop to very low levels. The behavior of the enzymatic state varies with the ethnic group studied. In those adults with low lactase activity little information is availalbe as to the age at which the lactase decreases. We attempted to determine a) the frequency of low intestinal lactase activity and b) the age at which the change occurs. For this purpose we reviewed in a large number of intestinal biopsies both histologically as well as for disaccharidase activities. The biopsies were obtained from a heterogeneous group of Caucasians, including patients, their siblings and parents. The patients were those with failure to thrive in whom no organic cause could be elicited, and those with the irritable colon syndrome. Patients ranged in age from 6 weeks to 50 years and out of a total of 1, 077 jejunal biopsies, 172 morphologically normal biopsies were selected. The milk drinking habits of 118 subjects and their families were elicited and 31 oral lactose tolerance tests performed. The mucosal lactase activity and sucrase-to-lactase ratio in those 172 individuals were plotted against age. In the first 3 years the mean lactase activity was 32.1 plus or minus 10.1 mumoles/g protein per min and the sucrase-to-lactase ratio was 1.7 plus or minus 0.5 with no change from year to year. However, after age 5 two separate groups emerge. A small group (24.6% of the population) with low lactase activity, and a second group possessing the same mean value for lactase activity as noted in the first 3 years. The low lactase activity group included children and adults with clinical lactose intolerance. These individuals consumed relatively small amounts of milk and when 12 of them were tested with an oral lactose tolerance test the result was a "flat" curve with a maximum rise in blood glucose of 9 plus or minus 3.2 mg/100 ml. The second group consumed more milk averaging 1 quart/day with no discomfort and when 19 were tested with oral lactose tolerance tests the values were normal. This study indicates that low lactase activity in the Caucasian population may make its appearance at the age of 5 years.

Adolescent↗
PubMed1977

Lactose malabsorption in adult Vietnamese.

Because of the traditional "nonmilking" attitude in Vietnam, a high incidence of lactose malabsorption would be expected in Vietnamese. However, confirming data are not available, and for this reason 31 adult Vietnamese were studied by obtaining diet histories and performing oral lactose tolerance tests. Twenty-three had drunk from one glass of milk a month to three glasses a day as adutls in Vietnam, and eight had noted milk-related symptoms. Since arrival in the United States, 30 had drunk milk and six had experienced symptoms. All 31 adult Vietnamese tested had flat lactose tolerance tests, signifying lactose malabsorption, with 20 subjects having symptoms during or after the tests.

Adult↗
PubMed1978

Blood glucose rise after lactose tolerance testing in infants.

Lactose tolerance tests are used clinically to screen children and infants. It is assumed that absorption of a lactose challenge in infants would occur in a predictable pattern prior to weaning. Twenty-one infants from 3 to 12 months of age were studied. The maximum blood glucose rise over fasting levels ranged from 11.0 to 62.0 mg/100 ml; the mean was 32.6 mg/100 ml. Six infants had a maximum rise of less than 20 mg/100 ml. Eleven infants (52%) had a maximum rise of greater than 30 mg/100 ml. Signs of intolerance were not noted in any subject. Weight and length were normally disturbed. Results indicate the variance in glucose rise existing within a population of infants growing normally and consuming milk. Gastric emptying, digestion, and absorption may influence the blood glucose rise after a lactose test. Established glucose levels used as an index to lactose absorption in older children and adults may not accurately reflect lactase activity in infants.

Blood Glucose↗
PubMed1979

Lactose malabsorption among Masai children of East Africa.

There is much disagreement about milk and its use in feeding programs both in the United States and internationally. A few authors suggest that milk consumption should not be encouraged in lactose intolerant populations due to adverse symptoms. Others suggest, however, that small or modest quantities of milk can be tolerated and can be nutritionally useful to such groups. Data are presented in this paper that show that 1) the Masai regularly drink considerable quantities of milk without apparent symptoms, 2) milk is an important constituent of the Masai diet, and 3) 62% of 21 Masai examined were malabsorbers of lactose as measured by the lactose tolerance test. This finding of lactose malabsorption in a nomadic cattle raising and milk drinking people is interesting and is contrary to the views often expressed by anthropologists and others. An ability to drink nutritionally useful quantities of milk does not, however, necessarily mean that milk production or imports should be encouraged in the Lesser Developed Countries.

Adolescent↗
PubMed1980

Breath hydrogen test after oral lactose in postgastrectomy patients.

The purpose of this study was to compare breath hydrogen tests after oral lactose ingestion in nonoperated subjects and postgastrectomy patients. Simultaneous oral lactose tolerance tests and breath hydrogen tests were performed in 50 subjects. Twenty of the 30 subjects without prior gastric surgery had normal lactase activities and low breath hydrogen concentrations. The other 10 subjects had low lactase levels and increased breath hydrogen concentrations. The remaining 20 subjects had prior gastric surgery. Seven of these had normal lactase activities, no history of milk intolerance and low breath hydrogen concentrations. Two of the postgastrectomy patients had low intestinal lactases, milk intolerance, and high breath hydrogens. The remaining 11 postgastrectomy patients had normal intestinal lactases but high breath hydrogens. Eight of the 11 had milk intolerance while two of the other three had not consumed milk since childhood. From these studies the following conclusions can be reached: 1)a low lactose breath hydrogen test in the postgastrectomy subject correctly identifies the individual with normal lactase activity. However, high breath hydrogen responses, may be found in either those with lactase deficiency or normal lactase activity. 2) Lactose malabsorption would appear to explain the milk intolerance in the postgastrectomy patient with normal lactase activity.

Animals↗
PubMed1980

Double blind study of milk lactose intolerance in a group of rural and urban children.

Two-hundred forty rural and 101 urban children were studied in a double blind fashion to determine their clinical response to three types of milk. Each participant received in three different days, 250 ml of lactose free milk, regular milk, and lactose enriched milk. In the urban girls a control period in which no milk was given was included. In both study groups, lactose free milk was highly significantly better tolerated than the others. However, the frequency of subjects asymptomatic after its ingestion was much lower, particularly in the rural group, to that found previously in a group of adults of high socioeconomic status. It is thought that in the rural children, part of this phenomenon can be explained by intercurrent gastrointestinal infections. There also appears to be a "background" of gastrointestinal symptoms present in the children, which wrongly classifies them as symptomatic to milk ingestion. It is concluded that probably no less than 15% of children have gastrointestinal complaints after the ingestion of 250 ml of regular milk and that lactose hydrolyzed milk is highly significantly better tolerated than the others.

Adolescent↗
PubMed1984

The effect of dietary lactose on the early recovery from protein-energy malnutrition. I. Clinical and anthropometric indices.

To assess the advisability of using lactose-containing formulas in the rehabilitation of severely malnourished children, indices of clinical recovery, growth and restoration of body proteins and gastrointestinal function were measured longitudinally during the initial 45 days of hospitalization in 20 male, preschool children with kwashiorkor and marasmic-kwashiorkor. All patients received a diet based on cows' milk, but half were allocated to a formula pretreated with beta-galactosidase to hydrolyze the lactose, while the others received the untreated, intact milk. The groups were identical with respect to clinical criteria on admission. For the final 37 days of the protocol, the subjects received 4 g of protein and 150 kcal of energy per kg per day. More diarrhea was experienced by the intact lactose group during early hospitalization. Overall, recovery was satisfactory in both cohorts, and there were no differences in rates of growth, body protein repletion, restoration of energy reserves nor intestinal functions. In conclusion, the routine reduction of lactose content from a milk-based diet for severe protein-energy malnutrition offers no advantages.

Animals↗
PubMed1985

Dietary manipulation of postprandial colonic lactose fermentation: II. Addition of exogenous, microbial beta-galactosidases at mealtime.

The feasibility and efficacy of adding microbial beta-galactosidase enzymes directly to milk at the time of consumption was explored in adult lactose-malabsorbers. The hydrogen breath test, and on one occasion, the rise in blood glucose, were used as indices of the completeness of intraintestinal hydrolysis and absorption of milk lactose. When added to 360 ml of cow milk containing 18 g of lactose, empirical dosages of three beta-galactosidases--one from Kluyveromyces (yeast) and two from Aspergillus (fungal)--had some effectiveness in reducing postprandial H2 excretion, although no in vivo treatment at the dosages chosen was as effective as pre-incubation of the milk in vitro. The yeast enzyme also reduced symptom frequency as compared to intact milk and enhanced postprandial rises in blood glucose. The replacement therapy with exogenous, food-grade beta-galactosidases may provide a useful intervention to reduce lactose malabsorption and milk intolerance in individuals with primary lactase deficiency.

Adult↗
PubMed1987

Lactose digestion by yogurt beta-galactosidase: influence of pH and microbial cell integrity.

Lactase-deficient subjects more effectively digest lactose in yogurt than lactose in other dairy products, apparently due to yogurt microbial beta-galactosidase (beta-gal) which is active in the GI tract. We evaluated the effects of buffering capacity of yogurt, gastric pH, and microbial cell disruption on beta-gal activity and lactose digestion. Three times more acid was required to acidify yogurt than to acidify milk. Yogurt beta-gal was stable at pH 4.0 but inactivated at lower pH. When yogurt was sonicated to disrupt microbial cell structure, only 20% activity remained after incubation at pH 4.0 for 60 min. In vivo gastric pH remained greater than 2.7 for 3 h after ingestion of yogurt. Acidified milk alone or with disrupted yogurt microorganisms caused twice as much lactose malabsorption as did acidified milk containing intact yogurt microorganisms. The results provide a possible explanation for the survival of beta-gal activity from yogurt in the GI tract.

Adult↗
PubMed1990

Effect of temperature on the lactose hydrolytic capacity of a lactase derived from Kluyveromyces lactis.

In vitro studies of lactose hydrolysis in milk with 20-125 neutral lactase units (NLUs) carried out at 38.0 degrees C for 15 min with a beta-galactosidase derived from Kluyveromyces lactis (Lactaid, Lactaid Inc, Pleasantville, NJ) resulted in 85-95% of the hydrolysis observed with standard incubation conditions (24 h at 4-5 degrees C with 1000 NLU/L). Thirty-three lactose-maldigesting Guatemalan subjects, 16 children and 17 adults, were challenged with oral doses of lactose in milk (children aged less than 12 mo, 2 g/kg body wt; children aged 12-24 mo, 15 g/kg body wt; older children and adults, 18 g/kg body wt) preincubated for 20 min at 38 +/- 0.5 degrees C with 50-125 NLU Lactaid. Under these conditions the subjects consumed milk without presenting any signs of intolerance. Furthermore, their breath-hydrogen excretion showed a 91-93% reduction when compared with a similar load of milk containing nonhydrolyzed lactose.

Adult↗
PubMed1980

Hypothesis is lactose a dietary risk factor for ischaemic heart disease?

The prevalence of primary adult lactose malabsorption (LM) in 23 ethnic groups was matched with national data on milk consumption and mortality rates from ischaemic heart disease (IHD). In 6 other ethnic groups prevalence of LM was related to unquantified assessments of milk consumption and frequency of IHD. On the available data, populations with a prevalence of LM over 30%, and whose consumption of milk is low or is largely in low lactose form, have a lower risk of IHD mortality than populations with a prevalence of LM under 30% and a high milk consumption. There is evidence against attributing these findings to genetic linkage between susceptibility to IHD mortality and persistent lactose absorption, or to differences in socio-economic development, cigarette consumption or intake of animal fats. The findings are compatible with an hypothesis that, if the correlation reported previously between milk consumption and IHD mortality is causal, lactose could be the responsible dietary factor.

Animals↗
PubMed2005

Molecularly-defined lactose malabsorption, milk consumption and anthropometric differences in adult males.

BACKGROUND: Lactose malabsorption (LM) may be associated with reduced skeletal calcium content. Diagnosis to date has been based on indirect methods, with a high false-negative rate. Identification of the LCT polymorphism led to development of a PCR-based test. AIM: To evaluate the PCR-based test compared to a combination the hydrogen breath test and the lactose tolerance test, and investigate anthropometrical differences, changes in bone mineral density and oral calcium intake according to LCT polymorphism and milk-drinking habits. METHODS: All participants (n = 278) underwent clinical examination, with measurement of height, weight and bone density (DXA), and were genotyped for LCT polymorphism (LCT CC or LCT TT: CC is associated with LM). A subgroup (n = 51) had a hydrogen breath test and a lactose tolerance test, in addition to genotyping. RESULTS: Detection of LM by LCT polymorphism was highly significant (p = 0.001). The correlation between LCT genotype and self-reported milk-intolerance or dislike of milk with was slight, but the correlation with functional tests was highly significant. Non-milk-drinkers were lighter (-5 kg) and significantly shorter (-4 cm) than milk-drinkers (p = 0.07 and 0.04, respectively). Total calcium consumption was lower among non-milk-drinkers by about 18% (p = 0.03). DISCUSSION: Genotyping is an economic, quick and convenient method for diagnosing lactose malabsorption, with results comparable to existing tests. Sufficient calcium consumption may be relevant to body growth, as milk-drinkers were taller. Negative calcium bone balance may be prevented when provision is made for adequate calcium intake.

Adult↗