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Lactase persistence or lactose tolerance is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk. In most mammals, ...
Lactase (EC 3.2.1.108) is an enzyme produced by many organisms and is essential to the complete digestion of whole milk.It breaks down the sugar lactose into its component parts, galactose and glucose.
Primary hypolactasia, or primary lactase deficiency, is genetic, develops in childhood at various ages, and is caused by the absence of a lactase persistence allele. In individuals without the lactase persistence allele, less lactase is produced by the body over time, leading to hypolactasia in adulthood.
The majority of humans actually follow this protocol as well, and down-regulate lactase production around 3-5 years of age. Interestingly, though, the majority of caucasians, mainly those from northern european background, continue to have elevated lactase activity all the way into adulthood, and so they exhibit “lactase persistence”.
Thomas has also worked extensively on the evolution of lactase persistence (see Lactose intolerance), the ability of some humans to produce the enzyme lactase throughout their adult life and thus to consume appreciable quantities of fresh milk without the discomforts of lactose malabsorption.
New research indicates that famine and exposure to infectious disease best explains the evolution of our ability to consume milk.
Lactase persistence One of the best known examples is the prevalence of the genotype for adult lactose absorption in human populations, such as Northern Europeans and some African societies, with a long history of raising cattle for milk.
Many adults are lactose intolerant because their bodies cease production of the enzyme lactase post childhood. However, mutations in the promoter region of the lactase gene (LCT) result in the continued production of lactase throughout adulthood in certain African populations, a condition known as lactase persistence. A study conducted by Sarah ...