Scientists have found out how drinking milk reduces the risk of developing diabetes

For many years, the debate about whether milk is good for adults or, on the contrary, harmful, has not subsided. Various arguments are given in favor of one theory or another. The only thing everyone agrees on is that it is better to avoid milk for people with lactase deficiency, who do not have the enzyme to process milk sugar.

In the journal Nature Metabolis, scientists published a sensational study: it turned out that drinking milk seriously reduces the risk of developing diabetes – and just in people with genetically determined lactase deficiency.

A team of medical researchers affiliated with several organizations in the US and China has found that the risk of developing type 2 diabetes is reduced in people with a certain gene variant if they regularly consume milk.

Scientists have tried to find a connection between milk consumption and a reduced risk of developing type 2 diabetes. To do this, they examined tissue samples collected from approximately 12.5 thousand Latino adults. As part of their work, they used dietary intake estimates developed by the US National Cancer Institute and determined the amount of dairy products consumed in daily servings, divided into the categories of milk, cheese and yogurt. And they found that in people with lactase deficiency who regularly consume milk, the risk of developing type 2 diabetes is reduced by 30%. No reduction in risk was observed in people who regularly consumed milk but did not have the LCT gene variant, which is responsible for lactase deficiency.

Lactase deficiency (lactose intolerance) is a condition in which the body is unable to digest milk sugar (lactose). Why? Because the intestines do not produce enough of a special enzyme – lactase. Most people produce lactase during childhood, but as many people grow older, their production stops, causing some to develop lactose intolerance.

In the Latin American population, the incidence of lactase deficiency is very high (approximately every second adult has it). They are likely lactose intolerant because they have inherited a variant of the lactase gene that makes them unable as adults to synthesize the enzyme needed to digest the milk sugar lactose. To bolster their findings, the team repeated their efforts with UK Biobank data and found similar results.

Digging deeper, the researchers found that for people with lactase intolerance, the potentially beneficial effects of milk consumption may be due to beneficial changes in their gut microbiota. These include, for example, the enrichment of beneficial Bifidobacterium species and the reduction of pathogenic Prevotella species. In addition, milk affects the level of metabolites circulating in the blood. If these results are confirmed, we could expect changes in dietary recommendations for people with lactose intolerance and lead to targeted use of probiotics to reduce the risk of developing type 2 diabetes in the general population.

According to the famous US geneticist Dmitry Prus, studies by nutritionists looking for risk factors for diabetes in food products have long revealed an unexpected pattern: consumption of dairy products was associated with a low risk of diabetes: “They tried to reproduce this discovery, but to no avail. The connection was not confirmed, and the hypothesis of the protective role of milk was forgotten. Maybe in vain. As it turns out, the association of milk with a reduced risk was observed mainly in Asia, and it was disproved in populations of European origin. There is a huge difference in the digestion of milk between the peoples of these countries: in Europe, genetic lactose tolerance is widespread, and in Asia, the lactase enzyme necessary for digesting milk sugar is not synthesized in almost any adult (and such people, in the absence of their own enzyme, help digest milk intestinal microflora). The new paper examines Latinos with their mixture of European and Paleo-Asian DNA, and immediately concludes that the protective effect of milk against the development of diabetes is very real, but exists only among people unable to synthesize lactase in adulthood. Their body weight and blood pressure are reduced. But no, not because they get continuous diarrhea from dairy foods. Analysis of the microflora and the enzymes produced by these bacteria leaves no doubt that those who continue to consume milk, despite genetic incompatibility, digest it quite normally with the help of “good microbes.” The microflora is dominated by bifidobacteria, and the levels of bacterial phospho-beta-galactosidase (replacing the missing lactase) are high. The authors also tried to find out what exactly these beneficial bacteria secrete to improve the health of milk drinkers, although their analysis of metabolites seemed less convincing to me.”

According to Russian geneticist Svetlana Borinskaya, lactase synthesis stops in Russians at about 22 years of age; among the Finns – at 25 years old, among the Chinese – at 6 years old. The scientist believes that the bacterial enzyme clarifies the mysteries of milk consumption by those whose lactase synthesis stops with age: “It would be interesting to also look at the age-related dynamics of the microflora. What happens to bifidobacteria in those who continue to drink milk and how different is it from those who stop?

According to leading experts dealing with lactase deficiency, among the adult population of Europe, lactose intolerance occurs in 1–7% of cases, and in Russia this figure ranges from 6 to 15%. You can understand whether you have lactase deficiency by passing a series of tests – for example, to determine total carbohydrates in stool, acidity (pH) of stool, hydrogen, methane or CO2 content in exhaled air, a glycemic load test with lactose. You can also take a genetic test.

In infants, lactase deficiency manifests itself with symptoms such as regurgitation, increased gas production, colic, diarrhea or constipation, and insufficient weight gain. In adults – increased gas formation, diarrhea and nausea.