Serum and Urine Metabolites in Healthy Men after Consumption of Acidified Milk and Yogurt.

The identification of molecular biomarkers that can be used to quantitatively link dietary intake to phenotypic traits in humans is a key theme in modern nutritional research. Although dairy products (with and without fermentation) represent a major food group, the identification of markers of their intake lags behind that of other food groups. Here, we report the results from an analysis of the metabolites in postprandial serum and urine samples from a randomized crossover study with 14 healthy men who ingested acidified milk, yogurt, and a non-dairy meal. Our study confirms the potential of lactose and its metabolites as markers of lactose-containing dairy foods and the dependence of their combined profiles on the fermentation status of the consumed products. Furthermore, indole-3-lactic acid and 3-phenyllactic acid are two products of fermentation whose postprandial behaviour strongly discriminates yogurt from milk intake. Our study also provides evidence of the ability of milk fermentation to increase the acute delivery of free amino acids to humans. Notably, 3,5-dimethyloctan-2-one also proves to be a specific marker for milk and yogurt consumption, as well as for cheese consumption (previously published data). These molecules deserve future characterisation in human interventional and observational studies.

Short-Term Dairy Product Elimination and Reintroduction Minimally Perturbs the Gut Microbiota in Self-Reported Lactose-Intolerant Adults.

An outstanding question regarding the human gut microbiota is whether and how microbiota-directed interventions influence host phenotypic traits. Here, we employed a dietary intervention to probe this question in the context of lactose intolerance. To assess the effects of dietary dairy product elimination and (re)introduction on the microbiota and host phenotype, we studied 12 self-reported mildly lactose-intolerant adults with triweekly collection of fecal samples over a 12-week study period: 2 weeks of baseline diet, 4 weeks of dairy product elimination, and 6 weeks of gradual whole cow milk (re)introduction. Of the 12 subjects, 6 reported either no dairy or only lactose-free dairy product consumption. A clinical assay for lactose intolerance, the hydrogen breath test, was performed before and after each of these three study phases, and 16S rRNA gene amplicon sequencing was performed on all fecal samples. We found that none of the subjects showed change in a clinically defined measure of lactose tolerance. Similarly, fecal microbiota structure resisted modification. Although the mean fraction of the genus Bifidobacterium, a group known to metabolize lactose, increased slightly with milk (re)introduction (from 0.0125 to 0.0206; Wilcoxon P = 0.068), the overall structure of each subject's gut microbiota remained highly individualized and largely stable in the face of diet manipulation. IMPORTANCE Lactose intolerance is a gastrointestinal disorder diagnosed with a lactose hydrogen breath test. Lifestyle changes such as diet interventions can impact the gut microbiome; however, the role of the microbiome in lactose intolerance is unclear. Our study assessed the effects of a 12-week dietary dairy product elimination and (re)introduction on the microbiome and clinical lactose intolerance status in 12 adult self-reported lactose-intolerant individuals. We found each subject's gut microbiome remained highly individualized and largely stable in the face of this diet manipulation. We also report that none of the subjects showed change in a clinically defined measure of lactose tolerance.

Stabilization of ß-Galactosidase on Modified Gold Nanoparticles: A Preliminary Biochemical Study to Obtain Lactose-Free Dairy Products for Lactose-Intolerant Individuals.

The unique chemical, optical, and electrical characteristics of nanoparticles make their utilization highly successful in every field of biological sciences as compared to their bulk counterpart. These properties arise as a result of their miniature size, which provides them an excellent surface area-to-volume ratio, inner structure, and shape, and hence increases their surface characteristics. Therefore, this study was undertaken to engineer gold nanoparticles (AuNPs) for improving their catalytic activity and stability in biotechnological processes. The characterization of AuNPs was performed by XRD, UV spectra, and TEM. The synthesized AuNPs were surface-modified by polyvinyl alcohol (PVA) for binding the enzyme in excellent yield. The developed immobilized enzyme system (PVA-AuNPs-ß-galactosidase) displayed pH optima at pH 7.0 and temperature optima at 40 °C. Moreover, the stability of PVA-AuNPs-ß-galactosidase was significantly enhanced at wider pH and temperature ranges and at higher galactose concentrations, in contrast to the free enzyme. ß-galactosidase bound to PVA-modified AuNPs exhibited greater operational activity, even after its sixth reuse. The developed nanosystem may prove useful in producing lactose-free dairy products for lactose-intolerant patients.

New insights into the molecular basis of lactase non-persistence/persistence: a brief review.

Lactose, a disaccharide and main carbohydrate in milk, requires hydrolysis in the intestinal tract to release its monosaccharides galactose and glucose for use as energy source by enterocytes. This hydrolysis is catalyzed by the enzyme lactase, a ß-galactosidase located in the brush border membrane of small intestinal enterocytes. In most mammals, lactase activity declines after the weaning, a condition known as lactase non-persistence (LNP). Lactase persistence (LP) is an autosomal dominant trait enabling the continued production of the enzyme lactase throughout adult life. Non-persistence or persistence of lactase expression into adult life being a polymorphic trait has been attributed to various single nucleotide polymorphisms in the enhancer region surrounding lactase gene (LCT). However, latest research has pointed to 'genetic-epigenetic interactions' as key to regulation of lactase expression. LNP and LP DNA haplotypes have demonstrated markedly different epigenetic aging as genetic factors contribute to gradual accumulation of epigenetic changes with age to affect lactase expression. This review will attempt to present an overview of latest insights into molecular basis of LNP/LP including the crucial role of 'genetic-epigenetic interactions' in regulating lactase expression.

Comparison of the impact of bovine milk ß-casein variants on digestive comfort in females self-reporting dairy intolerance: a randomized controlled trial.

BACKGROUND: Lactose malabsorption (LM) is a major cause of digestive discomfort from dairy products. Recently, a role for bovine ß-casein A1 has been proposed. OBJECTIVES: We examined whether there are distinct symptoms of digestive discomfort due to either lactose or differing bovine ß-casein types. METHODS: Women (n = 40; age: 25.2 ± 0.5 y) with self-reported varying dairy tolerance underwent a 50-g lactose challenge. Based on postchallenge LM and digestive discomfort, participants were classified as either lactose intolerant (LI; n = 10, self-reported intolerant, diagnosed lactose intolerant), nonlactose dairy intolerant (NLDI; n = 20, self-reported intolerant, diagnosed lactose tolerant), or dairy tolerant (DT; n = 10, self-reported tolerant, diagnosed lactose tolerant). In a double-blinded randomized sequence, participants consumed 750 mL conventional milk (CON; containing A1 and A2 ß-casein and lactose), a2 Milk (A2M; exclusively containing A2 ß-casein with lactose), or lactose-free conventional milk (LF-CON; containing A1 and A2 ß-casein without lactose). Subjective digestive symptoms and breath hydrogen (measuring LM) were recorded regularly over 3 h, and further ad hoc digestive symptoms over 12 h. RESULTS: LI subjects experienced prolonged digestive discomfort with CON milk. A2M reduced (P < 0.05) some symptoms (nausea: A2M 8 ± 3 mm compared with CON 15 ± 3mm; fecal urgency: A2M 4 ± 1 compared with CON 10 ± 3 mm), and attenuated the rise in breath hydrogen over 3 h, relative to CON milk (A2M 59 ± 23 compared with CON 98 ± 25 ppm at 150 min; P < 0.01). In contrast, NLDI subjects experienced rapid-onset, transient symptoms (abdominal distension, bloating, and flatulence) without increased breath hydrogen, irrespective of milk type. CONCLUSIONS: In LI individuals, LM and digestive comfort with lactose-containing milks was improved with milk containing exclusively A2 ß-casein. Furthermore, self-reported dairy intolerance without LM (NLDI) is characterized by early-onset digestive discomfort following milk ingestion, irrespective of lactose content or ß-casein type. This trial was registered at www.anzctr.org.au as ACTRN12616001694404.

Effects of Conventional Milk Versus Milk Containing Only A2 ß-Casein on Digestion in Chinese Children: A Randomized Study.

OBJECTIVES: In this study, we hypothesized that replacing conventional milk, which contains A1 and A2 ß-casein proteins, with milk that contains only A2 ß-casein in the diet of dairy or milk-intolerant preschoolers (age 5 to 6 years) would result in reduced gastrointestinal symptoms associated with milk intolerance, and that this would correspond with cognitive improvements. METHODS: This randomized, double-blind, crossover study aimed to compare the effects of 5 days' consumption of conventional milk versus milk containing only A2 ß-casein on gastrointestinal symptoms, as assessed via visual analog scales, average stool frequency and consistency, and serum inflammatory and immune biomarkers in healthy preschoolers with mild-to-moderate milk intolerance. The study also aimed to compare changes in the cognitive behavior of preschoolers, based on Subtle Cognitive Impairment Test scores. RESULTS: Subjects who consumed milk containing only A2 ß-casein had significantly less severe gastrointestinal symptoms as measured by visual analog scales, reduced stool frequency, and improvements in stool consistency, compared with subjects consuming conventional milk. There were significant increases from baseline in serum interleukin-4, immunoglobulins G, E, and G1, and beta-casomorphin-7 coupled to lower glutathione levels, in subjects consuming conventional milk compared with milk containing only A2 ß-casein. Subtle Cognitive Impairment Test analysis showed significant improvements in test accuracy after consumption of milk containing only A2 ß-casein. There were no severe adverse events related to consumption of either milk product. CONCLUSIONS: Replacing conventional milk with milk containing only A2 ß-casein reduced gastrointestinal symptoms associated with milk intolerance in Chinese preschool children, with corresponding improvements in aspects of cognitive performance.

Effects of Bifidobacterium longum and Lactobacillus rhamnosus on Gut Microbiota in Patients with Lactose Intolerance and Persisting Functional Gastrointestinal Symptoms: A Randomised, Double-Blind, Cross-Over Study.

Functional gastrointestinal symptoms are frequent, and may be driven by several pathogenic mechanisms. Symptoms may persist in lactose intolerant (LI) patients (i.e., subjects with intestinal lactase deficiency, lactose malabsorption producing symptoms), after a lactose-free diet. Our hypothesis was that probiotic and vitamin B6 treatment may be useful to alleviate symptoms in LI patients through a positive modulation of gut microbial composition and relative metabolism. We aimed to test the efficacy of a novel formulation of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 plus vitamin B6 (ZR) in 23 LI subjects with persistent symptoms during a lactose-free diet. Symptoms, microbiome, and metabolome were measured at baseline and after 30 days in a crossover, randomized, double-blind study of ZR versus placebo (PL). Compared with PL, the administration of probiotics and vitamin B6 significantly decreased bloating (p = 0.028) and ameliorated constipation (p = 0.045). Fecal microbiome differed between ZR and PL. ZR drove the enrichment of several genera involved in lactose digestion including Bifidobacerium. Moreover, the relative abundance of acetic acid, 2-methyl-propanoic acid, nonenal, and indolizine 3-methyl increased, while phenol decreased. Our findings highlight the importance of selected probiotics and vitamin B6 to alleviate symptoms and gut dysbiosis in lactose intolerant patients with persistent functional gastrointestinal symptoms.

Assessment of lactase activity in humans by measurement of galactitol and galactonate in serum and urine after milk intake.

Background: Lactase is an enzyme that hydrolyzes lactose into glucose and galactose in the small intestine, where they are absorbed. Hypolactasia is a common condition, primarily caused by genetic programming, that leads to lactose maldigestion and, in certain cases, lactose intolerance. Galactitol and galactonate are 2 products of hepatic galactose metabolism that are candidate markers for the intake of lactose-containing foods. Objectives: The primary objective of the study was to explore the changes in serum and urine metabolomes during postprandial dairy product tests through the association between lactase persistence genotype and the postprandial dynamics of lactose-derived metabolites. Methods: We characterized the 6-h postprandial serum kinetics and urinary excretion of lactose, galactose, galactitol, and galactonate in 14 healthy men who had consumed a single dose of acidified milk (800 g) which contained 38.8 g lactose. Genotyping of LCT-13910 C/T (rs4988235) was performed to assess primary lactase persistence. Results: There were 2 distinct postprandial responses, classified as high and low metabolite responses, observed for galactose, and its metabolites galactitol and galactonate, in serum and urine. In all but 1 subject, there was a concordance between the high metabolite responses and genetic lactase persistence and between the low metabolite responses and genetic lactase nonpersistence (accuracy 0.92), galactitol and galactonate being more discriminative than galactose. Conclusions: Postprandial galactitol and galactonate after lactose overload appear to be good proxies for genetically determined lactase activity. The development of a noninvasive lactose digestion test based on the measurement of these metabolites in urine could be clinically useful. This trial was registered at clinicaltrials.gov as NCT02230345.

Application of a commercial digestive supplement formulated with enzymes and probiotics in lactase non-persistence management.

Strategies to avoid lactose malabsorption, which affects 70% of the world's population, are focused on the restriction of milk and dairy products or the use of non-human ß-galactosidases or probiotics endowed with ß-galactosidase activity added at mealtime. Our evaluation of a commercial blend of probiotics and enzymes (protease, lactase, lipase and amylase) and its potential application in lactase non-persistence management is described in this work. Recommended amounts (460-1000 mg) of the commercial probiotics-enzyme blend were shown to be adequate for performing in vitro lactose hydrolysis in standard solutions (0.25-5%) and commercial dairy products, namely milks (5% lactose) and yogurts (3% lactose), reaching hydrolysis values between 44 and 96%. According to these percentages, the use of the enzymatic preparation would guarantee the intake of less than 12 g, the recommendation of the EFSA for lactose intolerance. Furthermore, formation of prebiotic galactooligosaccharides was also detected, increasing the potential benefits of the enzymatic preparation in the gastrointestinal system.

Lactose Breath Test in Children: Relationship Between Symptoms During the Test and Test Results.

BACKGROUND: Lactose malabsorption affects 70% of the world population. The hydrogen breath test (HBT) is used clinically to test for this condition. The aim of our study was to describe the relationship between symptoms experienced before and during the HBT and test results. METHODS: We included children who underwent the HBT in the pediatric gastroenterology unit at Dana-Dwek Children's Hospital during a 6-month period. Previous symptoms and those experienced before and after the HBT were assessed using a questionnaire and a validated pain scale. RESULTS: Ninety-five children were included in the study, and 66.3% had a positive HBT. Diarrhea and flatulence during the test were significantly more frequent in the group with a positive HBT compared to those with a negative test (31.7% vs. 9.4%, P = 0.016 and 69.8% vs. 40.6%, P = 0.006, respectively). The frequency of abdominal pain and bloating was similar. CONCLUSIONS: Diarrhea and flatulence during the HBT are the most specific symptoms of lactose intolerance. Abdominal pain should not be automatically attributed to lactose intolerance even in the presence of lactose malabsorption. Coupling the HBT with a real-time questionnaire facilitates interpretation of results and subsequent recommendations.

The Relationship Between the Human Genome and Microbiome Comes into View.

The body's microbiome, composed of microbial cells that number in the trillions, is involved in human health and disease in ways that are just starting to emerge. The microbiome is assembled at birth, develops with its host, and is greatly influenced by environmental factors such as diet and other exposures. Recently, a role for human genetic variation has emerged as also influential in accounting for interpersonal differences in microbiomes. Thus, human genes may influence health directly or by promoting a beneficial microbiome. Studies of the heritability of gut microbiotas reveal a subset of microbes whose abundances are partly genetically determined by the host. However, the use of genome-wide association studies (GWASs) to identify human genetic variants associated with microbiome phenotypes has proven challenging. Studies to date are small by GWAS standards, and cross-study comparisons are hampered by differences in analytical approaches. Nevertheless, associations between microbes or microbial genes and human genes have emerged that are consistent between human populations. Most notably, higher levels of beneficial gut bacteria called Bifidobacteria are associated with the human lactase nonpersister genotype, which typically confers lactose intolerance, in several different human populations. It is time for the microbiome to be incorporated into studies that quantify interactions among genotype, environment, and the microbiome in order to predict human disease susceptibility.

Predictors of response to a low-FODMAP diet in patients with functional gastrointestinal disorders and lactose or fructose intolerance.

BACKGROUND: Diets low in fermentable sugars (low-FODMAP diets) are increasingly adopted by patients with functional gastrointestinal disorders (FGID), but outcome predictors are unclear. AIM: To identify factors predictive of an efficacious response to a low-FODMAP diet in FGID patients with fructose or lactose intolerance thereby gaining insights into underlying mechanisms. METHODS: Fructose and lactose breath tests were performed in FGID patients to determine intolerance (positive symptom score) and malabsorption (increased hydrogen or methane concentrations). Patients with fructose or lactose intolerance consumed a low-FODMAP diet and global adequate symptom relief was assessed after 6-8 weeks and correlated with pre-diet clinical symptoms and breath test results. RESULTS: A total of 81% of 584 patients completing the low-FODMAP diet achieved adequate relief, without significant differences between FGID subgroups or types of intolerance. Univariate analysis yielded predictive factors in fructose intolerance (chronic diarrhoea and pruritus, peak methane concentrations and fullness during breath tests) and lactose intolerance (peak hydrogen and methane concentrations and flatulence during breath tests). Using multivariate analysis, symptom relief was independently and positively predicted in fructose intolerance by chronic diarrhoea [odds ratio (95% confidence intervals): 2.62 (1.31-5.27), P = 0.007] and peak breath methane concentrations [1.53 (1.02-2.29), P = 0.042], and negatively predicted by chronic nausea [0.33 (0.16-0.67), P = 0.002]. No independent predictive factors emerged for lactose intolerance. CONCLUSIONS: Adequate global symptom relief was achieved with a low-FODMAP diet in a large majority of functional gastrointestinal disorders patients with fructose or lactose intolerance. Independent predictors of a satisfactory dietary outcome were only seen in fructose intolerant patients, and were indicative of changes in intestinal host or microbiome metabolism.

Recent advances on lactose intolerance: Tolerance thresholds and currently available answers.

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.

[Correlation between the presence and intensity of symptoms and the results of hydrogen breath tests in the diagnosis of carbohydrate intolerance]. / Correlación entre los síntomas digestivos y los resultados de una prueba de hidrógeno en aliento en el diagnóstico de intolerancia a carbohidratos.

BACKGROUND: Hydrogen breath tests (HBT) are used to confirm the diagnosis of carbohydrate intolerance or small intestinal bacterial overgrowth (SIBO). OBJECTIVE: Determine the existence of a correlation between the presence and intensity of symptoms experimented by the patient after the ingestion of a carbohydrate load and the test result. MATERIALS AND METHODS: This is an observational, retrospective and analytic study, in which all patients' files from year 2008 to 2014 containing a report of a HBT performed at Hospital San José TEC de Monterrey were revised. Using a visual analogue scale (VAS), the patient reported the intensity of gastrointestinal symptoms during the test. Descriptive statistics were obtained, and exclusively for lactose HBTs, Pearson's correlation coefficient (r) between maximum hydrogen concentration in breath and symptom intensity was calculated. RESULTS: A HBT was performed in 33 patients: 23 with lactose, 5 with fructose, and 5 with lactulose as substrate. Of these, 10, 2, and 5 tests were positive, respectively. For lactose HBTs, the symptom with most sensitivity was flatulence (80%), which also had the greatest likelihood ratio for a positive test (1.73). Diarrhea had the greatest specificity (84.6%). A tendency for positivity was observed when patients presented symptoms. A moderately positive correlation between hydrogen ppm and symptom intensity was found (r=0.427, p=0.023). CONCLUSIONS: A correlation between symptom intensity and test positivity was found in patients with lactose intolerance. The presence of flatulence after lactose loading may be indicative of a positive test.

Accuracy of a Genetic Test for the Diagnosis of Hypolactasia in Chilean Children: Comparison With the Breath Test.

BACKGROUND: Lactase nonpersistence (LNP) in humans is a genetically determined trait. This age-dependent decrease of lactase expression is most frequently caused by single nucleotide polymorphisms in the regulatory region of the lactase (LCT) gene. The homozygous LCT-13,910C/C genotype (rs 4988235) predominates in Caucasian adults with LNP, and is useful for its diagnosis in this population. The accuracy of this genetic test (GT) has not been completely established in children or in a Latin-American population. OBJECTIVES: The aim of the study was to determine diagnostic accuracy of GT for LNP in Chilean children using the lactose breath test (BT) as a reference, and to compare diagnostic yield in preschool- (<6 years) and in school-age (≥6 years) children. METHODS: Children referred for BT for diagnosis of lactose malabsorption to the Gastroenterology Laboratory at Clínica Alemana, Santiago, from October 2011 to March 2012 were invited to participate. After informed consent, symptom questionnaires, both historic and post lactose ingestion were completed. H2 and CH4 in expired air and -13,910 C>T single nucleotide polymorphism by polymerase chain reaction, restriction enzyme analysis, and/or Sanger sequencing were determined. GT accuracy was calculated compared to BT as reference method. Diagnostic yield of GT in preschool- and school-age children was compared. RESULTS: Lactose malabsorption was detected by BT in 42 of 60 children (70%). Genotype -13,910C/C was identified in 41 of 60 patients (68%). GT showed 80% sensitivity, 63% specificity, and 74% accuracy for LNP in the preschool population. In school-age children values were higher, 85%, 80%, and 84%, respectively. CONCLUSIONS: GT results were significantly concordant with BT results for hypolactasia detection in Chilean children, particularly in those of age 6 years and older.

[Lactose intolerance: past and present. Part II]. / A laktózintoleranciáról: Múlt és jelen - II. rész.

The author summarises the interrelations between lactose intolerance, calcium and vitamin D metabolism and osteoporosis. Lactose intolerance enhances the risk of forearm and hip fractures in some patients. Lactase gene genotype and fracture risk are related in some populations. Calcium and vitamin D supplementation increase bone mineral content and they are justified in children, during pregnancy and lactation, and in postmenopausal women. The intake of milk and milk products could increase the risk of ovarian carcinoma. CC genotype of the lactase gene increased the risk of colorectal carcinoma in Finns; no such effect was observed in British, Spanish and Italian patients. Even small quantities of lactose in drugs (10-750 mg) could elicit intolerance symptoms due to individual susceptibility. In spite of public knowledge and advertising, controlled studies did not prove the beneficial effect of either a lactose-free diet, enzyme supplementation or probiotics in an evidence-based manner. While accepted guidelines are lacking, a personalised therapy is mandatory. In spite of increasing public interest in lactose intolerance, many unknown factors must still be studied.

Additional Value of CH4 Measurement in a Combined (13)C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis.

The lactose hydrogen breath test is a commonly used, non-invasive method for the detection of lactose malabsorption and is based on an abnormal increase in breath hydrogen (H2) excretion after an oral dose of lactose. We use a combined (13)C/H2 lactose breath test that measures breath (13)CO2 as a measure of lactose digestion in addition to H2 and that has a better sensitivity and specificity than the standard test. The present retrospective study evaluated the results of 1051 (13)C/H2 lactose breath tests to assess the impact on the diagnostic accuracy of measuring breath CH4 in addition to H2 and (13)CO2. Based on the (13)C/H2 breath test, 314 patients were diagnosed with lactase deficiency, 138 with lactose malabsorption or small bowel bacterial overgrowth (SIBO), and 599 with normal lactose digestion. Additional measurement of CH4 further improved the accuracy of the test as 16% subjects with normal lactose digestion and no H2-excretion were found to excrete CH4. These subjects should have been classified as subjects with lactose malabsorption or SIBO. In conclusion, measuring CH4-concentrations has an added value to the (13)C/H2 breath test to identify methanogenic subjects with lactose malabsorption or SIBO.