Lactose is the main carbohydrate present in milk. Mammalian offspring are able to digest it thanks to lactase into simpler sugars (glucose and galactose) that are easily absorbed in the intestine. There are certain genetic variants that could explain why some people find it easier to digest lactose in adulthood while others end up developing intolerance.
Lactose intolerance
Lactose intolerance is one of the most common food intolerances that occurs with decreased lactase activity in the epithelium of the small intestine and is manifested when the body reacts pathologically to milk sugar. It should not be confused with cow's milk allergy, which occurs by other mechanisms involving the immune system.
Symptoms can vary markedly within and between individuals and usually appear immediately or a few hours after ingestion of milk or milk products (yogurt, cheese, cream) or other foods containing lactose (such as cakes, ice cream or chocolate). Stomach pain, nausea, diarrhea and gas are characteristic signs of lactose intolerance. The intensity of the discomfort may vary from case to case.
Genes analyzed
MCM6
Bibliography
Anguita-Ruiz A., Aguilera C.M., et al. Genetics of Lactose Intolerance: An Updated Review and Online Interactive World Maps of Phenotype and Genotype Frequencies. Nutrients. 2020 Sep; 12(9): 2689.
Itan Y, Jones BL, Ingram CJ, et al. A worldwide correlation of lactase persistence phenotype and genotypes. BMC Evol Biol. 2010 Feb 9;10:36.
Lewinsky RH, Jensen TG, Møller J, et al. T-13910 DNA variant associated with lactase persistence interacts with Oct-1 and stimulates lactase promoter activity in vitro. Hum Mol Genet. 2005 Dec 15;14(24):3945-53.
