To compare sensitivity, specificity and convenience, four indirect methods of detecting lactase deficiency were tested prospectively in 25 subjects with biopsy-proved lactase deficiency and in 25 with normal lactase activity. After ingestion of 50 g of lactose, containing 1–14C lactose, breath hydrogen was abnormally elevated in all 25 lactase-deficient subjects (>0.30 ml per minute at two hours); breath 14CO2 was below the normal range in 23, and in 19 the plasma glucose increased by less than 20 mg per deciliter. When lactose and ethanol were given together, the rise in plasma galactose remained <5 mg per deciliter in 24 of the lactase-deficient subjects. The specificity of the four tests was excellent, with only one false-positive plasma glucose test. Measurement of breath hydrogen is sensitive and specific, and does not require ethanol or isotopes. It is noninvasive, and is not influenced by gastric emptying or metabolic factors. We believe it to be the most suitable test for population scree...

Prospective Comparison of Indirect Methods for Detecting Lactase Deficiency

The principal conclusion reached in Part I of this article (1) was that the group differences found in primary adult lactose intolerance among the world's peoples are largely genetic in origin. In this part, after a review of recent research that adds to Part I in important ways, we turn to a consideration of the conditions of genetic selection that may have led some groups of men to have persistently high levels of intestinal lactase throughout life, and others not. Low incidence of intolerance, it is held, would develop over time in a group that has an abundant milk supply, that has alternate foodstuffs inadequate in amount and quality, and that consumes milk in lactose-rich forms. Since such selection cannot have occurred among groups that did not use milk, areas of nonmilking in the modern world are first delimited. The origins and diffusion of dairying are then sketched to determine the length of time that milk was consumed in various regions. With the background thus gained, the present-day occurrence of various Old World groups with high and low incidences of intolerance is explained. All groups studied so far within the traditional areas of nonmilking are found to have high incidences of intolerance. Overseas groups, such as American Negroes, whose ancestors came from nonmilking regions also have high incidences of intolerance. Within the areas of milking in Africa and Europe, moreover, the known group differences in tolerance are found to be in accord with the hypothesis. Then, that the hypothesis may further be confirmed, specific additional research efforts are suggested.

Primary adult lactose intolerance and the milking habit : a problem in biologic and cultural interrelations II. A culture historical hypothesis

Summary: Since the discovery in 1899 of bifidobacteria as numerically dominant microbes in the feces of breast-fed infants, there have been numerous studies addressing their role in modulating gut microflora as well as their other potential health benefits. Because of this, they are frequently incorporated into foods as probiotic cultures. An understanding of their full interactions with intestinal microbes and the host is needed to scientifically validate any health benefits they may afford. Recently, the genome sequences of nine strains representing four species of Bifidobacterium became available. A comparative genome analysis of these genomes reveals a likely efficient capacity to adapt to their habitats, with B. longum subsp. infantis exhibiting more genomic potential to utilize human milk oligosaccharides, consistent with its habitat in the infant gut. Conversely, B. longum subsp. longum exhibits a higher genomic potential for utilization of plant-derived complex carbohydrates and polyols, consistent with its habitat in an adult gut. An intriguing observation is the loss of much of this genome potential when strains are adapted to pure culture environments, as highlighted by the genomes of B. animalis subsp. lactis strains, which exhibit the least potential for a gut habitat and are believed to have evolved from the B. animalis species during adaptation to dairy fermentation environments.

Genomic Insights into Bifidobacteria

Reviewed in this article is evidence bearing on the geographic hypothesis advanced eight years ago to explain the striking ethnic or racial differences in prevalence of primary adult lactose malabsorption that are found around the world. Most evidence is found to support the hypothesis and the likelihood that some human groups came to have low prevalences of such lactose malabsorption because of selective pressures over a long historical period that favored the adult lactose absorber under particular ecological conditions.

The geographic hypothesis and lactose malabsorption. A weighing of the evidence.

Intolerance to certain foods can cause a range of gut and systemic symptoms. The possibility that these can be caused by lactose has been missed because of “hidden” lactose added to many foods and drinks inadequately labelled, confusing diagnosis based on dietary removal of dairy foods. Two polymorphisms, C/T13910 and G/A22018, linked to hypolactasia, correlate with breath hydrogen and symptoms after lactose. This, with a 48 hour record of gut and systemic symptoms and a six hour breath hydrogen test, provides a new approach to the clinical management of lactose intolerance. The key is the prolonged effect of dietary removal of lactose. Patients diagnosed as lactose intolerant must be advised of “risk” foods, inadequately labelled, including processed meats, bread, cake mixes, soft drinks, and lagers. This review highlights the wide range of systemic symptoms caused by lactose intolerance. This has important implications for the management of irritable bowel syndrome, and for doctors of many specialties.

https://pmj.bmj.com/content/postgradmedj/81/953/167.full.pdf

DeanH. Lockwood

Papers

LACTASE DEFICIENCY IN THE ADULT: A Common Occurrence