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Differential impact of lactose/lactase phenotype on colonic microflora.

ABSTRACT: 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 maldigesters 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 unitsg 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 scorestogether, 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.

SUBMITTER: Szilagyi A

PROVIDER: S-EPMC2898492 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Differential impact of lactose/lactase phenotype on colonic microflora.

Szilagyi Andrew A Shrier Ian I Heilpern Debra D Je Jung J Park Sunghoon S Chong George G Lalonde Catherine C Cote Louis-Francois LF Lee Byong B

Canadian journal of gastroenterology = Journal canadien de gastroenterologie 20100601 6

<h4>Background</h4>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.<h4>Objective</h4>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 supporte ...[more]

PMID: 20559580

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Project description:BackgroundAdult lactase non-persistence (LNP) is due to low lactase expression, resulting in lactose malabsorption (LM). LNP is a genetic trait, but is typically determined by LM markers including breath H2, blood glucose, and urinary galactose after a lactose tolerance test. Known validity of these markers using milk is limited, despite being common practice. Compositional variation, such as ?-casein variants, in milk may impact diagnostic efficacy. This study aimed to evaluate the diagnostic accuracy to detect LNP using these commonly measured LM markers after both lactose and milk challenges.MethodsFourty healthy young women were challenged with 50?g lactose then randomized for separate cross-over visits to ingest 750?mL milk (37.5?g lactose) as conventional (both A1 and A2 ?-casein) and A1 ?-casein-free (a2 Milk™) milk. Blood, breath and urine were collected prior to and up to 3?h following each challenge. The presence of C/T13910 and G/A22018 polymorphisms, determined by restriction fragment length polymorphism, was used as the diagnostic reference for LNP.ResultsGenetic testing identified 14 out of 40 subjects as having LNP (C/C13910 and G/G22018). All three LM markers (breath H2, plasma glucose and urinary galactose/creatinine) discriminated between lactase persistence (LP) and LNP following lactose challenge with an area under the receiver operating characteristic (ROC) curve (AUC) of 1.00, 0.75 and 0.73, respectively. Plasma glucose and urinary galactose/creatinine were unreliable (AUC?<?0.70) after milk ingestion. The specificity of breath H2 remained high (100%) when milk was used, but sensitivity was reduced with conventional (92.9%) and a2 Milk™ (78.6%) compared to lactose (sensitivities adjusted for lactose content). The breath H2 optimal cut-off value was lower with a2 Milk™ (13?ppm) than conventional milk (21?ppm). Using existing literature cut-off values the sensitivity and specificity of breath H2 was greater than plasma glucose to detect LNP following lactose challenge whereas values obtained for urinary galactose/creatinine were lower than the existing literature cut-offs.ConclusionThis study showed accurate diagnosis of LNP by breath H2 irrespective of the substrate used, although the diagnostic threshold may vary depending on the lactose substrate or the composition of the milk.Trial registrationACTRN12616001694404 . Registered prospectively on December 9, 2016.

Project description:Abstract Objectives Lactase persistence (LP), a heritable trait in which lactose can be digested throughout adulthood, is often used to predict dairy intake. However, it is currently unknown how LP relates to daily lactose consumption in healthy US adults. The objective of the study was to estimate lactose from foods reported in the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24) and to compare lactose and total dairy consumption in relation to LP genotypes. Methods ASA24 dietary data were collected from healthy Caucasians and Hispanics (n = 215) genotyped for the lactase persistence SNP ID: rs4988235. ASA24 outputs servings of dairy but not the nutrient lactose. Lactose was estimated by matching ASA24-reported foods to foods in the Nutrition Coordinating Center Food and Nutrient Database, which outputs lactose. Analysis of covariance was used to identify whether genotype influenced lactose and total dairy consumption with total energy intake and weight as covariates. Pairwise testing was conducted on the adjusted means using the Tukey adjustment to correct for multiple testing. Results Median lactose consumption for subjects with the AA genotype (homozygous LP) was 12.08 g (min: 0.91 g, max: 81.85 g), 10.05 g (min: 0.46 g, max: 45.82) for subjects with the AG genotype (heterozygous LP), and 8.97 g (min: 0.47, max: 38.96 g) for subjects with the GG genotype (homozygous lactase non-persistent). AA subjects consumed more lactose than GG subjects (P = 0.024). When stratifying by sex, there were no significant differences among genotypes in women, although GG women consumed the least amount of lactose compared to AA and AG women. AA men consumed more lactose than AG (P = 0.028) and GG men (P = 0.032). Subjects with the AA genotype consumed the most, and GG subjects the least amount of dairy. However, there were no significant differences in total dairy consumption among genotypes. Conclusions The median amount of lactose consumed daily by healthy adults is 9–12 g/day, with higher consumption by those with an LP genotype. Total dairy intake was not significantly influenced by genotype, highlighting the value in specifically estimating lactose consumption. Maximal lactose intake by lactase non-persisters exceeding 15 g/day suggests alternate routes of lactose catabolism. Funding Sources The California Dairy Research Foundation and the USDA-ARS.

Project description:BackgroundThe ability of adult humans to digest the milk sugar lactose - lactase persistence - is a dominant Mendelian trait that has been a subject of extensive genetic, medical and evolutionary research. Lactase persistence is common in people of European ancestry as well as some African, Middle Eastern and Southern Asian groups, but is rare or absent elsewhere in the world. The recent identification of independent nucleotide changes that are strongly associated with lactase persistence in different populations worldwide has led to the possibility of genetic tests for the trait. However, it is highly unlikely that all lactase persistence-associated variants are known. Using an extensive database of lactase persistence phenotype frequencies, together with information on how those data were collected and data on the frequencies of lactase persistence variants, we present a global summary of the extent to which current genetic knowledge can explain lactase persistence phenotype frequency.ResultsWe used surface interpolation of Old World lactase persistence genotype and phenotype frequency estimates obtained from all available literature and perform a comparison between predicted and observed trait frequencies in continuous space. By accommodating additional data on sample numbers and known false negative and false positive rates for the various lactase persistence phenotype tests (blood glucose and breath hydrogen), we also apply a Monte Carlo method to estimate the probability that known lactase persistence-associated allele frequencies can explain observed trait frequencies in different regions.ConclusionLactase persistence genotype data is currently insufficient to explain lactase persistence phenotype frequency in much of western and southern Africa, southeastern Europe, the Middle East and parts of central and southern Asia. We suggest that further studies of genetic variation in these regions should reveal additional nucleotide variants that are associated with lactase persistence.

Dataset Information

Differential impact of lactose/lactase phenotype on colonic microflora.

Publications

Differential impact of lactose/lactase phenotype on colonic microflora.

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