Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, inc...

Total lactase and sucrase activities in the mucosa of the small intestine were determined from four pigs of the Hampshire (H), Duroc (D) and Yorkshire (Y) breeds at approximately 6 months of age. All pigs were fed a conventional 14% protein corn-soybean meal diet. Lactase (g lactose hydrolyzed/24 hr) and sucrase (g sucrose hydrolyzed/24 hr) activity differed (P<.01) among breeds, as Y had 2.5fo...

Lactase-phlorizin hydrolase (LPH), a membrane-bound glycoprotein present in the luminal surface of enterocytes in the intestine is responsible for lactose intolerance, a phenomenon prevalent in humans worldwide. In the rodent intestine, the post-natal development of the LPH follows a specific pattern, such that the enzyme levels are high in the peri-natal period, but declines considerably upon ...

BACKGROUND Urinary excretion of D-xylose by suckling rats after ingestion of a mixture of 4-, 3-, and 2-galactosylxyloses reflects lactase activity in vivo. We aimed to select the most convenient of these disaccharides for detecting changes of the enzyme activity in vivo and to optimize the method. METHODS 4-, 3-, and 2-galactosylxyloses were synthesized and purified, then orally administered...

I write in response to the article by Rasinperä and colleagues (Gut 2004;53:1571–6) in which a DNA test was proposed for ‘‘adulttype hypolactasia’’. The ability to digest the milk sugar lactose as an adult (lactase persistence) is a variable genetic trait in human populations, lactase persistence being the most frequent phenotype in Northern Europe, while lactase nonpersistence or ‘‘adult-type ...

In the experiments reported in the preceding paper (p. 597) it was found that lactose, fed to hens, does not appear in the excreta in appreciable quantities until excessive amounts are administered—a finding thoroughly in agreement with our present knowledge of sugar-feeding in human beings. Since lactose is assimilated from the alimentary canal of chickens, and since assimilation of disacchari...

Objective: Milk is an important source of nutrients. However the consumption of milk may cause abdominal complaints in lactose intolerant individuals. It is known that frequency of 13910C/C genotype is high among Northern Russians and exceeds the prevalence in northern Europe. In our study we tested two hypothesis 1) subjects with lactase non-persistent genotype (13910C/C) have more symptoms as...

Background and aims: The role of nutrition in the pathogenesis of colorectal cancer is not fully understood. Milk products are an essential part of human nutrition in Western countries. Absorption of lactose, the main sugar of milk, is regulated by the activity of the lactase enzyme in the gut wall. The activity of lactase is genetically determined and is associated with a C/T single nucleotide...

BACKGROUND The lactase enzyme allows lactose digestion in fresh milk. Its activity strongly decreases after the weaning phase in most humans, but persists at a high frequency in Europe and some nomadic populations. Two hypotheses are usually proposed to explain the particular distribution of the lactase persistence phenotype. The gene-culture coevolution hypothesis supposes a nutritional advant...