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PubMed1978

Co-induction of beta-galactosidase and the lactose-P-enolpyruvate phosphotransferase system in Streptococcus salivarius and Streptococcus mutans.

The addition of lactose, galactose, or isopropyl-beta-D-thiogalactoside (IPTG) to glucose-grown cells of Streptococcus salivarius 25975 resulted in the co-induction of both the lactose-P-enolpyruvate phosphotransferase system (lactose-PTS) and beta-galactosidase, with the latter the predominant metabolic system. With various strains of Streptococcus mutans and Streptococcus sanguis 10556, on the other hand, the lactose-PTS was the major metabolic pathway with beta-galactosidase induced either to low or negligible levels. In all cases, induction of the lactose-PTS resulted in the concomitant induction of 6-P-beta-galactosidase. The induction by lactose of both the lactose-PTS and beta-galactosidase in all strains was repressed by glucose and other catabolites, notably, fructose. Induction of beta-galactosidase in S. salivarius 25975 by IPTG was, however, relatively resistant to glucose repression. Induction experiments with IPTG and lactose suggested that a cellular metabolite of lactose metabolism was a repressor of enzyme activity. Exogenous cAMP was shown to reverse the transient repression by glucose of beta-galactosidase induction in cells of S. salivarius 25975 receiving lactose, provided the cells were grown with small amounts of toluene to overcome the permeability barrier to this nucleotide, cAMP, was however, unable to overcome the permanent repression of beta-galactosidase activity to a significant extent under these conditions.

Cyclic AMP↗
PubMed1990

Binding-protein-dependent lactose transport in Agrobacterium radiobacter.

Agrobacterium radiobacter NCIB 11883 was grown in lactose-limited continuous culture at a dilution rate of 0.045/h. Washed cells transported [14C]lactose and [methyl-14C]beta-D-thiogalactoside, a nonmetabolisable analog of lactose, at similar rates and with similar affinities (Km for transport, less than 1 microM). Transport was inhibited to various extents by the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, by unlabeled beta-galactosides and D-galactose, and by osmotic shock. The accumulation ratio for methyl-beta-D-thiogalactoside was greater than or equal to 4,100. An abundant protein (molecular weight, 41,000) was purified from osmotic-shock fluid and shown by equilibrium dialysis to bind lactose and methyl-beta-D-thiogalactoside, the former with very high affinity (binding constant, 0.14 microM). The N-terminal amino acid sequence of this lactose-binding protein exhibited some homology with several other sugar-binding proteins from bacteria. Antiserum raised against the lactose-binding protein did not cross-react with two glucose-binding proteins from A. radiobacter or with extracts of other bacteria grown under lactose limitation. Lactose transport and beta-galactosidase were induced in batch cultures by lactose, melibiose [O-alpha-D-galactoside-(1----6)alpha-D-glucose], and isopropyl-beta-D-thiogalactoside and were subject to catabolite repression by glucose, galactose, and succinate which was not alleviated by cyclic AMP. We conclude that lactose is transported into A. radiobacter via a binding protein-dependent active transport system (in contrast to the H+ symport and phosphotransferase systems found in other bacteria) and that the expression of this transport system is closely linked to that of beta-galactosidase.

Amino Acid Sequence↗
PubMed2000

Control of lactose transport, beta-galactosidase activity, and glycolysis by CcpA in Streptococcus thermophilus: evidence for carbon catabolite repression by a non-phosphoenolpyruvate-dependent phosphotransferase system sugar.

Streptococcus thermophilus, unlike many other gram-positive bacteria, prefers lactose over glucose as the primary carbon and energy source. Moreover, lactose is not taken up by a phosphoenolpyruvate-dependent phosphotransferase system (PTS) but by the dedicated transporter LacS. In this paper we show that CcpA plays a crucial role in the fine-tuning of lactose transport, beta-galactosidase (LacZ) activity, and glycolysis to yield optimal glycolytic flux and growth rate. A catabolite-responsive element (cre) was identified in the promoter of the lacSZ operon, indicating a possible role for regulation by CcpA. Transcriptional analysis showed a sevenfold relief of repression in the absence of a functional CcpA when cells were grown on lactose. This CcpA-mediated repression of lacSZ transcription did not occur in wild-type cells during growth on galactose, taken up by the same LacS transport system. Lactose transport during fermentation was increased significantly in strains carrying a disrupted ccpA gene. Moreover, a ccpA disruption strain was found to release substantial amounts of glucose into the medium when grown on lactose. Transcriptional analysis of the ldh gene showed that expression was induced twofold during growth on lactose compared to glucose or galactose, in a CcpA-dependent manner. A reduced rate of glycolysis concomitant with an increased lactose transport rate could explain the observed expulsion of glucose in a ccpA disruption mutant. We propose that CcpA in S. thermophilus acts as a catabolic regulator during growth on the preferred non-PTS sugar lactose. In contrast to other bacteria, S. thermophilus possesses an overcapacity for lactose uptake that is repressed by CcpA to match the rate-limiting glycolytic flux.

Bacterial Proteins↗
PubMed1962

Permeability and metabolism of lactose in Neurospora crassa.

Lester, G. (Worcester Foundation for Experimental Biology, Shrewsbury, Mass.), D. Azzena, and O. Hechter. Permeability and metabolism of lactose in Neurospora crassa. J. Bacteriol. 84:217-227. 1962.-Germinated conidia of Neurospora crassa suspended in buffer take up lactose, and this uptake can be attributed to the intracellular accumulation and to the metabolism of lactose. The former process predominates initially, and the latter after a few hours of incubation. The accumulation of lactose appears to be mediated by a very specific transport system, which can bring about intracellular concentrations that greatly exceed the external concentration of lactose. Both the influx and efflux of lactose appear to be dependent on metabolic energy, since azide and low temperature inhibit these events. The steroid hormone 11-deoxycorticosterone also reduces the uptake and prevents the accumulation of lactose. The metabolism of lactose was clearly demonstrated, but the pathway(s) of metabolism was not defined. The amount of beta-galactosidase activity extractable from the cells was insufficient to be solely responsible for the initial step in lactose metabolism. The present studies are discussed in relationship to ion permeability and lactose metabolism in N. crassa, and to galactoside permeability in Escherichia coli.

Biological Transport↗
PubMed1993

pH changes in human dental plaque from lactose and milk before and after adaptation.

pH changes in human dental plaque in vivo from lactose and milk have been studied in four separate mouthrinse experiments. (1) pH was measured in plaque samples of 12 subjects before and after 6 weeks of frequent daily mouthrinsing with 10% lactose. The pH decreases were significantly more pronounced after the adaptation period than before (p < 0.001), 4 of the 12 subjects showing about the same low plaque pH from lactose as from glucose. (2) Similar to the previous experiment, frequent daily mouthrinsing with low-fat bovine milk in 10 subjects resulted in more pronounced pH decreases in plaque after an adaptation period of 4 weeks (p < 0.001). (3) Single mouthrinses, without any prior adaptation, with bovine standard milk, human breast milk, lactose-hydrolysed bovine standard milk, 5% lactose and 5% sucrose were compared regarding the effect on plaque pH in 7 subjects. All solutions resulted in pH falls. The most pronounced were found with sucrose, followed by the lactose-hydrolysed milk. (4) Bovine standard milk, 5% lactose and 10% sucrose were compared after a single mouthrinse in 5 subjects using interdental plaque pH wire telemetry. Lactose and milk were fermented more slowly than sucrose. In a separate study, acid production from lactose was also measured in two oral strains each of Streptococcus mutans, Streptococcus salivarius and Streptococcus sanguis. The results from these experiments indicated that at least part of the lactose transport and catabolism in all studied streptococcus strains seems to be regulated by inducible enzymes.

Adaptation, Biological↗
PubMed1993

Lactose flux occurs by differing mechanisms in the colon and jejunum of newborn piglets.

The unidirectional flux of 10- and 40-mM lactose was studied in newborn porcine jejunum and colon mounted in Ussing chambers. Polyethylene glycol 400 was used to measure passive paracellular permeability. The mucosal-to-serosal flux and the tissue accumulation of labeled lactose from the colon was similar to that of lactose-derived glucose from the jejunum. However, only jejunum showed a lactose-stimulated increase in short-circuit current. In jejunum, glucose was the sole sugar identified in the serosal bath, whereas in colon, only intact lactose was identified. Despite colonic lactose flux, polyethylene glycol oligomers were not found in the serosal bath, suggesting that they do not share the same route of absorption. Colonic lactose transport was nonsaturable between 1 and 40 mM. Under nongradient conditions, no net colonic lactose transport was observed. Cumulatively, these data suggest that the colon, unlike the jejunum, does not contain a glucose-galactose sodium cotransporter. The colon of the newborn piglet transports intact lactose at a flux equal to that of lactose-derived glucose by the small intestine, but by a different mechanism that is as yet undefined.

Animals↗
PubMed2005

The protective effect of lactose on lyophilization of CNK-20402.

The goal of this research was to assess the feasibility of using lyophilization to stabilize an exploratory compound, CNK-20402, with a minimal amount of impurity (CNK-20193) formation. A mixed-level full factorial experimental design was used to screen excipients of glycine, mannitol, lactose monohydrate, and povidone K-12. Cryostage microscopy, powder x-ray diffraction, Karl Fischer titration, HPLC, and water vapor sorption were used to assess the formulations' physicochemical properties and stability. Initial physical characterization from powder x-ray diffraction revealed that the mannitol- and glycine-containing formulations were crystalline with the patterns of the pure excipient, whereas the remaining formulations were amorphous in structure. Chemically, the formulations stored at 50 degrees C for 1 month had 2.36%, 1.05%, 0.81%, 0.79%, and 0.49% CNK-20193 for glycine, mannitol, drug alone, povidone K-12, and lactose formulations, respectively. The formulations containing drug-mannitol, drug alone, and drug-lactose were selected for accelerated stability study based on statistical analysis. Recovery of CNK-20193 in these formulations was 1.22%, 1.00%, and 0.55%, respectively, when stored at 40 degrees C/75% relative humidity storage conditions for 3 months. Water vapor sorption analysis revealed weight gains of over 7%, 21%, and 24% for the mannitol, lactose, and drug alone formulations, respectively. Testing formulations with different concentrations of lactose by water vapor sorption indicated that CNK-20402 concentrations as low as 10% (wt/wt) could inhibit the recrystallization of lactose. The lactose-containing formulation exhibited the best stability among the formulations tested. The protective mechanism of lactose on the CNK-20402, based on water vapor sorption studies, is believed to be a result of (1) the drug-lactose interaction, and (2) competition between lactose and drug for the residual water in the formulation.

Chemistry, Pharmaceutical↗
PubMed2002

Effect of levels of starch, fiber, and lactose on digestion and growth performance of early-weaned rabbits.

The effect of source of carbohydrate on gut histology, digestion efficiency, and growth performance in early-weaned (25 d) rabbits at the starter period (25 to 39 d) was investigated. Six diets were factorially arranged to study the effect of partial substitution of starch (0, 25, or 50%) by lactose at two levels of fiber (30 or 36% NDF). Diets were formulated to meet or exceed essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of treatments on growth performance in 252 rabbits that were fed the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Fecal apparent digestibility was determined at 35 d of age in nine animals per diet. The four diets with extreme lactose content were used to determine ileal apparent digestibility of starch and lactose (nine replicates per diet), weights of stomach and cecum, stomach pH, cecal fermentation traits, amylase and disaccharidase activities (10 animals per diet), and jejunal morphology (six animals per diet). Weaning increased (P < 0.001) amylase activity by 59% but decreased (P < 0.001) maltase, sucrase, and lactase activities by 30, 48, and 72%, in parallel with a reduction of villus height by 19%. Dietary NDF level did not affect either jejunal morphology or sucrase and lactase activities but increased amylase (P = 0.05) and maltase (P < 0.001) activities by 22 and 92%, respectively. Substitution of starch by lactose had no effect on jejunal morphology or enzymatic activity. Ileal lactose and starch digestibility were not affected by dietary NDF or lactose level and averaged 73.8 and 90.8%, respectively. Substitution of starch by fiber and lactose affected ileal flux of starch plus lactose (by -0.5 and +1.7 g/d) and cecal pH (by +2.1 and -2.8%, respectively). Fecal NDF digestibility was relatively low (23.1% on average) and was not affected by treatments, whereas that of lactose and starch was almost complete. An increase of dietary NDF level led to an impairment of ADG and feed efficiency in the starter (P < 0.002) and in the overall (P < 0.03) fattening period. Substitution of starch by lactose linearly decreased (P < 0.001) feed efficiency in the starter period and linearly increased (P < 0.001) diarrhea incidence in the fattening period. The results indicate that digestive capability of early-weaned rabbits is limited and should be taken into account to establish optimal levels and sources of carbohydrates in the starter diet.

Animal Feed↗
PubMed1980

Effect of lactose supplement on digestion of lucerne hay by sheep. I. Sites of organic matter and nitrogen digestion.

Lactose was added (400 g/day, as powder) to a lucerne hay diet (700 g/day, chopped). The two diets (hay and hay with lactose) were fed twice daily, successively, to four adult sheep fitted with rumen cannulas and simple cannulas at the proximal and at the distal end of the small intestine. Organic matter (OM) intake was 544 g/day with hay and 961 g/day with hay and lactose. Addition of lactose increased the proportion of OM that disappeared within the rumen (45.7 vs 38.7%) and within the small intestine (18.3 vs 13.2%), and decreased amounts that disappeared in the large intestine (6.7 vs 9.0%). However, the differences were not significant. Lactose was almost entirely fermented in the rumen, resulting in low pH and high lactate concentration for 3 hr after meals. Mean volatile fatty acid (VFA) concentrations were low (67 mmoles/liter) and unchanged by addition of lactose. Propionate and valerate molar proportions increased and acetate molar proportions decreased with lactose supplementation. Adding large amounts of readily fermentable carbohydrates as lactose greatly altered nitrogen digestion of the lucerne hay in the rumen; supplementation allowed a greater uptake of ammonia for microbial synthesis. Consequently, rumen ammonia levels, blood urea and urinary nitrogen excretion decreased greatly with lactose, from 20.5 mg/100 ml, 20.6 mg/100 ml and 6.96 g/day to 2.3 mg/100 ml, 8.7/100 ml and 2.5 g/day, respectively. The amount of nitrogen flowing into the duodenum increased by 47%, and the amount of nonammonia nitrogen apparently digested within the small intestine by 83%. Nitrogen in feces increased with lactose because of increased microbial nitrogen. Retained nitrogen increased only slightly (from 5.0 to 6.4 g/day) because of the low nitrogen needs of sheep.

Animal Feed↗
PubMed2006

Analysis of milk urea nitrogen and lactose and their effect on longevity in Canadian dairy cattle.

The aim of this study was to assess the phenotypic level of lactose and milk urea nitrogen concentration (MUN) and the association of these traits with functional survival of Canadian dairy cattle using a Weibull proportional hazards model. A total of 1,568,952 test-day records from 283,958 multiparous Holstein cows from 4,758 herds, and 79,036 test-day records from 26,784 multiparous Ayrshire cows from 384 herds, calving from 2001 to 2004, were used for the phenotypic analysis. The overall average lactose percentage and MUN for Ayrshires were 4.49% and 12.20 mg/dL, respectively. The corresponding figures for Holsteins were 4.58% and 11.11 mg/dL. Concentration of MUN increased with parity number, whereas lactose percentage decreased in later parities. Data for survival analysis consisted of 39,536 first-lactation cows from 1,619 herds from 2,755 sires for Holsteins and 2,093 cows in 228 herds from 157 sires for Ayrshires. Test-day lactose percentage and MUN were averaged within first lactation. Average lactose percentage and MUN were grouped into 5 classes (low, medium-low, medium, medium-high, and high) based on mean and standard deviation values. The statistical model included the effects of stage of lactation, season of production, the annual change in herd size, type of milk-recording supervision, age at first calving, effects of milk, fat, and protein yields calculated as within herd-year-parity deviations, herd-year-season of calving, lactose percentage and MUN classes, and sire. The relative culling rate was calculated for animals in each class after accounting for the remaining effects included in the model. Results showed that there was a statistically significant association between lactose percentage and MUN in first lactation with functional survival in both breeds. Ayrshire cows with high and low concentration of MUN tended to be culled at a higher than average rate. Instead, Holstein cows had a linear association, with decreasing relative risk of culling with increasing levels of MUN concentration. The relationship between lactose percentage and survival was similar across breeds, with higher risk of culling at low level of lactose, and lower risk of culling at high level of lactose percentage.

Animals↗
PubMed1976

Effect of alcohols on lactose solubility.

In tests of effects of high (70 to 90% volume/volume) and low (2 and 5% volume/volume) alcohol concentrations, solubility of lactose decreased with increased alcohol concentration and decreased as alcohol chain length increased. Since lactose has lower solubility in alcohol, crystallization would be expected to be speeded by increased supersaturation. Composition of precipitates formed by the action of ethanol changed with time; alpha-lactose precipitated more rapidly at first, then beta-lactose. Time of crystallization was related directly to the percentage of beta-lactose (therefore, the relation was inverse for total alpha). However, the percentage of alpha-hydrate increased with time and with water content. Agitation during crystallization increased production of beta-lactose. Composition of the lactose precipitate varied greatly with concentration of alcohol (ethanol). When ethanol concentration was low, only alpha-hydrate was precipitated whereas at higher concentrations stable anhydrous alpha lactose also was precipitated, with the percentage of total alpha decreasing while the percentage of beta-lactose increased. Crystal shape changed from prisms initially to partially or fully developed tomahawks as time went by or as the percentage of ethanol decreased, and crystal color increased with crystallization time and as ethanol percentage decreased. Choosing long-chain alcohols and controlling suitable parameters enabled recovery of greater amounts and more desirable forms of lactose.

Alcohols↗
PubMedDate not supplied

Effect of dietary lactose on cecal pH, bacteriostatic volatile fatty acids, and Salmonella typhimurium colonization of broiler chicks.

One-day-old broiler chicks were inoculated with volatile fatty acid producing cecal flora from adult chickens. The chicks were divided into four groups and provided 1) no lactose, 2) 2.5% lactose in water, 3) 5% lactose in feed, or 4) 10% lactose in feed, until 10 days of age. All groups were challenged at 3 days of age with 10(6) or 10(8) S. typhimurium. At 10 days, the number of Salmonella in the ceca of the chicks challenged with 10(6) Salmonella was significantly decreased (P less than 0.01) in the groups provided lactose as compared with the controls. A significant decrease (P less than 0.01) in Salmonella numbers occurred in the chicks challenged with 10(8) Salmonella and provided 10% lactose. Providing 2.5% lactose or 5% lactose failed to inhibit Salmonella growth in chicks challenged with 10(8) Salmonella. The pH of the ceca of the groups provided lactose decreased significantly (P less than 0.05) and was accompanied by significant increases (P less than 0.01) in the concentrations of bacteriostatic acetic and propionic acids. Results showed that providing dietary lactose to broiler chicks and inoculation with normal cecal flora decreased cecal pH, increased the concentrations of bacteriostatic volatile fatty acids, and inhibited Salmonella colonization.

Animals↗
PubMed1989

Clinical and nutritional consequences of lactose feeding during persistent postenteritis diarrhea.

In a double-blind prospective trial, 64 children, 3 to 36 months of age, who had diarrhea for at least 14 days were randomly assigned to receive either a milk-based diet containing 6 g/kg of body weight per day of lactose or the same diet in which the lactose was greater than 95% prehydrolyzed with beta-galactosidase. Clinical and nutritional outcomes were compared. The groups were similar at the start of the study. Four of 33 patients (12.1%) in the lactose group were considered to have treatment failure because of excessive purging with or without refusal to accept the diet, compared with 1 of 31 patients (3.2%) in the hydrolyzed lactose group (P = .20). Among successfully treated boys, fecal excretion was initially similar, but on days 3 to 5 of the trial the lactose group purged a mean 74.4 g/kg per day (95% confidence limits 17.8, 131.0) compared with 42.0 g/kg per day (95% confidence limits 11.4, 72.6) in the hydrolyzed lactose group (P less than .01). Diarrhea stopped within 30 hours of hospital admission in 11 children in the hydrolyzed lactose group (35.5%) compared with 1 child in the lactose group (3.3%) (P less than .001). Fecal excretion of carbohydrate, nitrogen, and energy was significantly greater in lactose group (P less than .01), but there were no significant differences in fat excretion or in incremental weight change during hospitalization. Feeding lactose-containing nonhuman milk as the sole nutrient source to children with persistent diarrhea resulted in substantially greater purging which was sufficiently severe to increase the risk of dehydration in these children.

Animals↗
PubMed1988

Relationship between milk lactose tolerance and body mass in teenage Tswana schoolchildren.

The Tswana and other black races of southern Africa have a high prevalence of the adult type of primary lactose intolerance. It is possible that nutritional status may affect lactose absorption, so that lactose malabsorbers may be less well nourished than lactose absorbers. However, such a poor nutritional status may have caused, or have been caused by, the lactose malabsorption. It is also possible that another factor, such as chronic diarrhoea, may cause both poor nutrition and lactose intolerance. A random sample of 92 Tswana pupils was taken from a school population of 486. Their heights and weights were measured, and the relative weight and body mass index (weight/height2) calculated for each subject. A milk tolerance test was administered to each subject to establish whether they were lactose tolerant or intolerant. There were 79 (85.9%) lactose intolerant subjects, 7 (7.6%) were probably intolerant and only 6 (6.5%) were lactose tolerant. The nutritional status of the lactose intolerant and tolerant subjects were compared. The two groups did not differ in nutritional status, as measured by their relative weights and body mass indices, and were nutritionally similar to a reference population of Tswana schoolchildren.

Adolescent↗
PubMed1995

Colchicine-induced lactose malabsorption in patients with familial Mediterranean fever.

Abdominal pain and diarrhea are frequent side effects of chronic colchicine therapy. Drug-induced lactose deficiency has been demonstrated in the experimental animal. Lactose malabsorption was assessed by the lactose breath test in 23 patients with familial Mediterranean fever (FMF) receiving colchicine for 0.25-15 years (mean 3.16). Twenty FMF patients not receiving colchicine and 38 non-FMF lactose malabsorbers served as controls. Patients receiving colchicine had a significantly higher percentage of lactose malabsorption (20/23, 87%) versus nontreated FMF patients (13/20, 65%; P < 0.05). Lactose intolerance was also more prevalent in colchicine-treated patients (17/23, 74%) versus nontreated FMF (5/20, 25%; P < 0.0005) and control lactose malabsorbers (16/38, 42%; P < 0.01). Of the 12 patients investigated before and 3 months after colchicine administration, 7 showed induction or aggravation of lactose malabsorption. The lactose-free diet resulted in partial improvement of symptoms. Colchicine induces significant lactose malabsorption in FMF patients and this is partially responsible for the gastrointestinal side effects of the drug.

Abdominal Pain↗
PubMed1996

Evaluation of the pathogenesis of flatulence and abdominal cramps in patients with lactose malabsorption.

Aim of this study was to assess whether the interindividual differences in the development of flatulence and cramps in patients with lactose malabsorption are due to the quantity of malabsorbed lactose or gas accumulation, or if accelerated intestinal transit or increased perception of gas might play a role. Hydrogen breath tests were performed in 43 patients with lactose malabsorption after ingestion of 50 g lactose and, on a separate day, 25 g lactulose. The unabsorbed amount of lactose, small bowel transit time and colonic hydrogen accumulation were assessed in patients who did and did not develop flatulence and cramps after ingestion of lactose. The unabsorbed amount of lactose, small bowel transit time and volume and rate of colonic hydrogen accumulation were the same in patients who did or did not have symptoms after lactose. Patients with flatulence and cramps had a significantly longer time interval between the onset of the increase and peak breath hydrogen concentration (p < 0.05) and a significant correlation between the time of occurrence of peak symptoms and the time of peak breath hydrogen concentration (r = 0.75, p < 0.001). Our data suggest that subjective symptoms of lactose intolerance are not due to the amount of malabsorbed lactose or to the volume or rate of gas accumulation per se, but are related to increased perception of gas.

Adolescent↗
PubMed1996

Assessment of the influence of hydrogen nonexcretion on the usefulness of the hydrogen breath test and lactose tolerance test.

The recognition of hydrogen nonexcretion in up to 20% of tested subjects and the large ethnic differences in the prevalence of lactose malabsorption make it necessary to reassess the diagnostic usefulness of the lactose tolerance test and the hydrogen breath test. Both tests were performed in 83 consecutive patients with suspected lactose malabsorption who ingested 50 g lactose. On a separate day a hydrogen breath test was performed after 25 g lactulose. The prevalence of hydrogen nonexcretion was 18%. The diagnostic usefulness of hydrogen breath test was influenced both by the individual threshold for hydrogen excretion and the amount of malabsorbed lactose. In addition to baseline values, breath samples for hydrogen measurements have to be taken at 30, 60, 90, 180, and 240 minutes after ingestion of lactose. For the lactose tolerance test only one measurement of serum glucose at 30 minutes is needed in addition to the baseline measurement. The combination of both tests excludes the influence of hydrogen nonexcretion, but even if a combined diagnostic approach utilizing the lactose hydrogen breath test and lactose tolerance test is used, 6% of patients presenting with symptoms suggestive of lactose intolerance cannot be classified.

Adolescent↗
PubMed1995

Effect of yogurt on symptoms and kinetics of hydrogen production in lactose-malabsorbing children.

Lactase-deficient adults demonstrate improved lactose absorption and fewer symptoms when consuming yogurt than when consuming milk containing equivalent amounts of lactose. To examine this effect and its mechanisms in children, we compared symptoms and hydrogen production as an index of lactose malabsorption after typical servings of milk, pasteurized yogurt, and yogurt containing active live culture in 14 lactose-malabsorbing children (mean age 9.5 y). Symptoms and interval breath-hydrogen concentrations were recorded for 8 h after ingestion of 12 g lactose served as milk and yogurts. Lactose-malabsorbing children experienced significantly fewer symptoms after consuming yogurt containing active cultures than after consuming milk (P < 0.005). Pasteurized yogurt showed an intermediate effect. Lactose from yogurt was not better absorbed than was lactose from milk, as indicated by similar areas under the hydrogen curve; however, yogurt was associated with a delayed time to rise and lower rate of rise of the hydrogen curve. The rate of hydrogen rise correlated with the degree of symptoms. In children, mechanisms other than enhanced lactose absorption from yogurt may lead to changes in the kinetics of hydrogen production, which in turn are associated with improved tolerance.

Adolescent↗