What percentage of adults are lactose intolerant?

Lactose intolerance: 15 percent of Germans are affected

The milk sugar lactose, like the cane sugar sucrose or the malt sugar maltose, belongs to the disaccharides, which consist of two (= di) simple sugars (monosaccharides). Disaccharides ingested through food have to be broken down into monosaccharides in order to be able to pass through the intestinal wall. This happens through enzymes (ferments), in the case of milk sugar through the enzyme lactase. Lactose intolerance is caused by insufficient splitting of the disaccharide lactose into the monosaccharides glucose (grape sugar) and galactose in the small intestine. Due to a deficiency or an absence of this enzyme, the lactose reaches the large intestine without being broken down, where it is absorbed and fermented by intestinal bacteria.
The metabolic products produced during this process (short-chain fatty acids and gases containing hydrogen, acetate, butyrate and propionate) ultimately cause the symptoms typical of lactose intolerance, i.e. lactose intolerance, such as intestinal cramps, flatulence, diarrhea or nausea in some people. However, since these symptoms can also apply to other diseases of the gastrointestinal tract, a diagnostic differentiation of lactose intolerance from other diseases is important. However, it is also important to know that the majority of people do not develop symptoms of intolerance, even though they largely lack the enzyme and the lactose is not or insufficiently broken down in the small intestine.