Infant lactose intolerance is now no stranger. Simply put, lactose intolerance is caused by the fact that many people lack lactase in adulthood，which makes it impossible to digest lactose. Milk contains a lot of lactose, the consequences of an inability to digest are naturally caused by a series of gastrointestinal diacomforts such as abdominal distension and diarrhea.
Traditionally, lactose intolerance is associated with genes. In infancy, most people can produce lactase, which digests the lactose contained in breast milk daily. However, with the increase of age, the amount of lactase will gradually decrease. The degree of reduction varies from person to person, but about 65% of the world's population will have varying degrees of lactose intolerance in adulthood.
Of course, this ratio also has regional differences, such as more than 90% in Asia, but only about 5% in Northern Europe. The picture below is a good presentation. The lighter the area, the higher the proportion of people who are lactose intolerant treats.
Small partners should immediately turn to China. In most parts of China, lactose tolerance is only 10% to 20%. In other words, 89% of adults in China are lactose intolerant. How on earth did this figure come from?
Studies have shown that LCT is the gene responsible for lactase production in humans. Almost everyone has this gene, so it's okay for everyone to breast-feed in infancy. But as you get older, another gene called MCM6 slowly decreases the expression of LCT, resulting in less lactate production and naturally slowly lactose intolerance. It is in the MCM6 gene that those "lucky" lactose-tolerant individuals have a mutation that changes G at one locus into A, which impairs the function of MCM6, and LCT is able to function appropriately. Most of the evaluation of lactose tolerance is based on the sequencing of MCM6 locus. If it's AA or AG, then this person is lactose tolerant; if it's GG, it's lactose intolerant.
Then someone asked: However if 80% of people in China are lactose intolerant, why is the milk in the supermarket still selling so well? And there aren't so many lactose intolerances I have seen around me... This problem has also plagued scientists for many years, and traditional interpretations often refer to individual differences.
Because after all, everyone has a lactase-producing gene (LCT), even if MCM6 does not have a mutation, it can normally inhibit the expression of LCT, or it may not be completely inhibited due to individual differences, resulting in a few people who are not resistant to lactose. Accepted, but still can drink a little milk.
But a recent study gave a new explanation. The researchers analyzed the intestinal flora in many of the subjects and found that there was a bifidobacterium that appeared more frequently in subjects whose genotype was GG (that is, the gene showed lactose intolerance). At the same time, in the GG genotype test, there were more bifidobacteria in the intestine, and the dairy products consumed in the same period were also more.
This leads to another possible explanation: people with some GG genotypes, although they do not produce lactase at all, have a large number of bifidobacteria in their bodies, and bifidobacteria can digest lactose, thereby avoiding undigested lactose. Adverse effects on human intestines. Therefore, although these people do not produce lactase by themselves, they can still drink milk happily.
Therefore, people who are intolerant of lactose may rely on bifidobacteria in the intestines to help them drink more milk. Although there is no clinical experiment to confirm this, it is still a possible direction.
However, in the end, most of the "probiotic" products on the market, although they all contain bifidobacteria, bifidobacteria is a very picky type of bacteria, often need to survive under anaerobic conditions, and cryopreservation Also beneficial to bacterial activity. In addition, these probiotics that have been drunk can still enter the intestines after passing through the test of stomach acid, and the effectiveness is difficult to consider. It is still a little difficult to treat lactose intolerance by drinking probiotic beverages.