It was taken for granted: 10,000 billion bacteria live in our digestive system, and are therefore 10 times more numerous than all the cells in our body. For nearly 40 years, this established dogma has governed scientific studies interested in what researchers call the intestinal microbiota. But a new study, conducted by researchers in biochemistry, genetics and cell biology at the Weizmann Institute of Science in Rehovot (Israel) and the Hospital for Sick Children in Toronto (Canada) and published on the site bioRxiv, challenges this assumption.
Same number of bacteria as cells in the body?
The researchers scoured the scientific studies which have been interested in this subject since the one which is at the origin of this estimate, in 1972. This first work was done on the colon and had calculated the number of bacteria present in the digestive tract assuming the bacterial density was constant throughout the digestive system. However, according to the authors of this new study, the number of bacteria in the colon area is negligible compared to the volume of its contents. They then proposed a new method of calculation and arrived at the much less impressive result of 1.3 bacteria for 1 human cell, or an almost identical number for the two categories (against the 10 bacteria for 1 human cell previously established).
Reassess the role of the gut microbiota
These results have yet to be verified by other researchers before being published in a recognized scientific journal. But if they are validated, years of research on the intestinal flora could be reconsidered. The main question will then be whether such a reassessment of the number of bacteria contained in our intestines could call into question their demonstrated involvement in the diabetes, L’obesity, L’appetite, L’mood and even theautism.
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