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The normal mammalian condition is for the young to lose the ability to effectively digest milk sugar (lactose) at the end of the weaning period (a species-specific length of time usually equal to roughly 3% of lifespan). It has been established that certain human populations have undergone a mutation on chromosome 2 which results in a bypass of the normal shutdown in lactase production, allowing members of these groups to continue consumption of fresh milk and fresh milk products throughout their lives.
There is some debate on exactly where and when the mutation(s) occurred, some arguing for separate mutation events in Sweden and the Arabian Peninsula near 4000 BC which converged as they spread, while others argue for a single event in the Middle East at about 4500 BC which radiated from there. Whatever the precise origin, most western Eurasians and people of western Eurasian ancestry show the effects of this mutation while most eastern Eurasians, sub-saharan Africans and native peoples of the Americas and Pacific Islands do not [1].
Without lactase, the lactose in milk remains uncleaved and unabsorbed, and instead gut bacteria metabolise it, producing copious amounts of gas by fermentation. This causes a range of unpleasant abdominal symptoms, including stomach cramps, flatulence and diarrhea. Like other unabsorbed sugars, e.g. mannitolMannitol or 1,2,3,4,5,6-hexanehexol (CH(OH)) is a vasodilator which is used mainly to reduce pressure in the cranium, and to treat patients with oliguric renal failure. It can be administered intravenously. Chemically, mannitol is an alcohol and a sugar,, the lactose raises the osmotic pressure of the colonIn anatomy of the digestive system, the colon is the part of the intestine from the cecum to the rectum. Its primary purpose is to extract water from feces. In mammals, it consists of the ascending colon on the right side, the transverse colon, the descen contents, preventing the colon from resorbing water and hence causing a laxativeA laxative is a preparation used for the purpose of encouraging defecation, or the elimination of feces. Laxatives are most often taken in response to constipation. They are also sometimes used before medical procedures. They are often abused by bulimics effect to add to the excessive gas production.
One solution to this problem (other than avoiding milk) is lactose-free milk, which is produced by passing milk over lactase enzyme bound to an inert carrier: once the molecule is cleaved, there are no lactose ill-effects, whatever the milk drinker's ancestry. The milk sold for pet catFor alternative meanings see cat (disambiguation). The cat (also called domestic cat or house cat is a small feline carnivorous mammal. Its scientific name is Felis silvestris catus or Felis silvestris domesticus but the species is sometimes referred to as is another example of lactose reduced milk. Oddly, many European cat breeds have a mutation similar to the human mutation, also prevalent in EuropeFor the band of the same name, see Europe (band . Europe is a continent forming the westermost part of the Eurasian supercontinent. Europe is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Se, which allows symptom-free adult lactose consumption. Most oriental breeds are particularly sensitive to lactose.
In recent years ( 1990Events January January 3 Former leader of Panama Manuel Noriega surrenders to American forces. January 7 The Leaning Tower of Pisa is closed to the public due to safety concerns. January 9 Lt Gen Bazilio Olara Okello The man who led the coup aginst Dr Apo- 2000) there has been an increase in the number of lactose-reduced and lactose-free dairy products. Some of these products are cottage cheese, American cheese and ice cream. These products are made using milk substitute s such as soy milk, almond milk, or rice milk. Another recent solution has been a pill which artificially provides the missing enzyme, allowing a person to tolerate milk products for a period of a few hours after taking the pill.