Lactose intolerance is characterized by the presence of clinical signs, mainly gastrointestinal, resulting from colonic lactose fermentation. Lactose absorption is impaired due to the inability to express the enzyme that hydrolysed lactose in galactose and glucose in the small intestine. These clinical signs modify by several factors, including lactose dose, residual lactase expression, concomitant intake of other dwell components, intestinal transit time, and enteric microbiome composition.
Lactase Deficiency x Lactose Intolerance
Lactase deficiency is the main cause of lactose malabsorption. This is an enzyme produced by intestinal villi, capable of hydrolysing lactose in galactose and glucose. And how does that happen? High concentrations of lactase are usually present in newborns, but after weaning, their activity decreases in most people in a genetic and physiological way, leading to so-called primary lactose malabsorption. Secondary hypolactasia may result from any brush edge injury of the small intestine mucosa or increased gastrointestinal transit time. Lactose intolerance is defined when lactose malabsorption causes gastrointestinal symptoms such as occurrence of symptoms such as abdominal pain, bloating or diarrhea after lactose intake.
Most individuals with lactose malabsorption tolerate a dose of at least 12 g lactose (corresponding to 250 mL of milk) without problems. Higher doses can be tolerated if consumed with food or distributed for a full day. Therefore, the intensity of lactose intolerance symptoms depends on the strength of the stimulus (i.e., lactose dose). In addition, they also depend on the presence of visceral hypersensitivity, as observed in many patients with irritable bowel syndrome (ISS).
Treatment options for lactose intolerance include a low lactose diet and oral replacement of the lactase enzyme, primarily. In addition, prebiotics that produce bacterial lactase in the colon and potentially prebiotics that adapt to colonic microbiota can also be prescribed. However, intolerance to low to moderate lactose doses usually indicates the presence of ISI. Therefore, these individuals are also sensitive to a variety of poorly absorbed fermentable foods, ‘FODMAPs’. In this context, effective dietary treatment requires the adoption of a low-lactose diet with low FODMAP content, popularly known as the Low FODMAP diet.
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Genetics in Food Intolerances and Sensitivities
Article Lactose Intolerance: Misselwitz B, Butter M, Verbeke K, Fox MR. Update on lactose malabsorption and intolerance: pathogenesis, diagnosis and clinical management.
Gut. 2019 Nov;68(11):2080-2091. doi: 10.1136/gutjnl-2019-318404. Epub 2019 Aug 19. PMID: 31427404; PMCID: PMC6839734.