are asians lactose intolerant
But those allergic reactions are relatively rare, affecting an estimated 4% of adults. Milk's different. There are people who have true milk allergies that can cause deadly reactions. Instead, people who are lactose intolerant can't digest the main sugar —lactose— found in milk. In normal humans, the enzyme that does so —lactase— stops being produced when the person is between two and five years old. Lactose intolerance is most common among Asians, affecting more than 90 % of adults in some communities. People with ancestry from Northern Europe, on the other hand, have a 5% rate of lactose intolerance. The enzyme that splits lactose into glucose and galactose is called lactase, and it is located on the surface of the cells lining the small intestine. Lactose intolerance is caused by reduced or absent activity of lactase that prevents the splitting of lactose (lactase deficiency). But most people who have bad reactions to milk aren't actually allergic to it, in that it's not their immune system that's responding to the milk. Instead, people who are lactose intolerant can't digest the main sugar —lactose— found in milk. Approximately 75 % of Earths population is lactose intolerant for a reason, because it’s perfectly natural. The statistics vary from race to race and country to country but overall they show an abnormal amount of individuals who qualify. In some Asian countries, 90 percent of the population is lactose intolerant. Interestingly, we are the only species on the planet that drinks milk from another species. 1 Lactose intolerance is caused by a deficiency of the intestinal enzyme lactase that splits lactose into two smaller sugars, glucose and galactose, and allows lactose to be absorbed from the intestine.  The primary symptoms of lactose intolerance are diarrhea, flatulence (passing gas), and abdominal pain. An estimated 65% of human adults (and most adult mammals) downregulate [decrease] the production of intestinal lactase after weaning. Lactase is necessary for the digestion of lactose, the main carbohydrate in milk, and without it, milk consumption can lead to bloating, flatulence, cramps and nausea. Lactose intolerance percentages were taken directly from the source referenced. The fact that some percentages are exact and others are provided as a range is the result of the research methodologies used by the authors of the respective studies. 1 Lactose intolerance is treated with dietary changes, supplements of lactase enzyme, and adaptation to increasing amounts of milk.  Avoidance of milk and milk-containing products can lead to a dietary deficiency of calcium and vitamin D that, in turn, can lead to bone disease (osteoporosis). The enzyme responsible for breaking down lactose is lactase, an enzyme found on the wall of the intestines. Lactase breaks down lactose (the sugar found in milk) into galactose and glucose. The activity of lactase becomes reduced after breastfeeding, at that point the body no longer needs as much lactase. Not to mention a human mothers milk is much different from the milk of a cow. Since lactase’s only function is the digestion of lactose in milk, most mammal species experience a dramatic reduction in the activity of the enzyme after weaning. Lactase persistence in humans has evolved as an adaptation to the consumption of non-human milk and dairy products consumed beyond infancy.
Yes, it is most common among Asians, affecting more than 90 % of adults in some communities.