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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 , the activity of the enzyme is dramatically reduced after weaning . [ 1 ]
Some populations have developed genetic changes to allow the digestion of lactose: lactase persistence. [78] Other populations developed cooking methods like milk fermentation. [78] Lactase persistence in humans evolved relatively recently (in the last 10,000 years) among some populations.
Well, this group historically has domesticated cows and other milk providers and consumed lactose-based, or milk-based products into adulthood, and by natural selection, it’s thought that they’ve developed increased persistence of lactase production by specific gene mutations that are often autosomal dominant.
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 .
Lactose, or milk sugar, is a disaccharide composed of galactose and glucose and has the molecular formula C 12 H 22 O 11. Lactose makes up around 2–8% of milk (by mass). The name comes from lact (gen. lactis ), the Latin word for milk, plus the suffix -ose used to name sugars.
Lactose synthase is an enzyme that generates lactose from glucose and UDP-galactose.. It is classified under EC 2.4.1.22.. It consists of N-acetyllactosamine synthase and alpha-lactalbumin.
With the increasing consumption of milk products these societies developed a lactase persistence by epigenetic inheritance, which means that the milk-digesting enzyme lactase was present in their bodies during the whole lifetime, so they could drink unfermented milk as adults too.
[23] [24] In areas with lactase persistence, it is believed that by domesticating animals, a source of milk became available while an adult and thus strong selection for lactase persistence could occur; [21] [25] in a Scandinavian population, the estimated selection coefficient was 0.09-0.19. [25]