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Scientists: Obesity and Alzheimer's Disease Can Be Spread Through Microbiota
Scientists have put forward the theory that we can "get" from other people obesity, dementia, cardiovascular and some other diseases. This could potentially result from changes in the composition of the microbiota following the transfer of nominally harmless bacteria.
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Common sense and general knowledge of biology tells us that we can only contract infectious diseases from other people. A new article, which is published in the journal Science, casts doubt on this axiom. Scientists point out that the accumulated scientific evidence speaks in favor of the fact that we can "get" from other people obesity, dementia, cardiovascular and some other diseases. This could potentially result from changes in the composition of the microbiota following the transfer of nominally harmless bacteria.
In recent years, scientists have learned a lot about how microbiota (microorganisms that live in the human body and on its surface) affect health. For example, through research involving both humans and animals, we are aware of its role in obesity and heart disease. But the fact that it can take part in the transmission of noncommunicable diseases from person to person, scientists have not previously stated. They do not state this even now, but in a new article they indicate that this theory needs detailed research.
It is known that obesity can spread in certain groups of people. In 2007, a large study followed 12,000 people for 30 years and found that people who have an obese friend have a 57% higher risk of developing the condition. A similar phenomenon has been described for spouses.
In animal studies, transplanting microbiota from obese mice into healthy mice has been shown to dramatically increase the risk of obesity. Inverse experiments were also carried out: transplanting a healthy microbiota slowed down the progression of Alzheimer's disease and cardiovascular diseases in sick mice.
There are known, although not studied in detail, cases of transmission of microbiota from person to person: in utero from mother to child, transfer of fecal bacteria.
“If you add up this data, a promising concept emerges,” Brett Finlay, a professor at the University of British Columbia in Canada and lead author of the research, told Gizmodo.
The new theory is more complex than the theory of transmission of infectious diseases, which explains the role of viruses, bacteria and other pathogens. For example, obesity can indeed "spread" among certain groups of people. But the general environment and genetics can also influence the occurrence of this condition. At the same time, the environment and genetic factors influence the formation of the microbiota. If there is indeed a microbiota that increases the risk of Alzheimer's disease, that does not mean that after acquiring it, the person will develop the disease the next morning. Many chronic diseases take years or decades to develop. Not all people who have risk factors get sick.
Scientists emphasize that we are not talking about one harmful bacteria, but about changes at the level of the microbiome, which can change in many ways in its own way.
All these circumstances lead to the fact that the new theory is difficult to prove. Scientists have developed criteria for future research. They are based on the classic postulates of Robert Koch and other concepts to prove that a specific microorganism causes a specific disease.
“We applied general concepts of microbial transmission. The tricky part of this theory is to separate the effects of diet and the environment with those of the microbiota, since they are closely related,”said Finlay. He added that the new concept could have a big impact on healthcare.