Since Dutchman Antony van Leeuwenhoek discovered bacteria and protozoa for the first time ever in history in the 17th century, much has been learnt about the microscopic world we live in and the one that lives inside us. Our microbiota, and specially our gut microbiota, have been studied intensely over the past 15 years. A huge amount of data is regularly published establishing associations between its composition and our health, and alterations of its balance have been linked with diseases such as obesity, diabetes, asthma and cancer.
Nevertheless, some experts start to claim we have to be cautious, as this is a very new field, full of hope and promises yet to be scientifically demonstrated.
This is the case of Professor Patrice D. Cani, researcher from the Belgium Fund for Scientific Research (FRS-FNRS) from the Université catholique de Louvain, Brussels (Belgium). In a recent article in Gut, he provides a critical analysis of the current knowledge on gut microbiota and claims caution as the data we have today tend to create too much associations between bacteria as a causality for protection against disease or for the onset of a pathology. Other factors like genes, diet or stool frequency among others, can influence gut microbiota composition as well and should also be considered, he believes.
“I have been working in the field of obesity and diabetes for more than 20 years, and the same for microbiota, as many of my colleagues I have seen the field blooming. We need time to move to the application and be careful about translations that are not correct”, Cani warns.
In fact, although there are dozens of studies correlating the disturbance of gut microbiota composition to diseases, “the fact is we do not know yet whether it is more important the absolute quantity of microorganisms, or the proportion of every type of these microbes, or even their activity”, the Belgium expert states. It is a complex ecosystem in which several players are involved in the cross-talk.
We do know, for instance, the importance of some specific microbial components that have been discovered to contribute to the regulation of energy and the metabolism. In this sense, there are some studies based on solid evidence, some of them published by Cani himself, evaluating the key role gut microbiota play in obesity or type 2 diabetes.
But, as he poses in the article, what is the role of a single isolated bacteria among a big and complex community? For the moment, it is challenging to answer that question, as too often bacteria cannot be cultured in the lab, what makes it difficult to demonstrate their action through experiments.
All in all, concludes Cani , we are living with a tremendous number of microorganisms in our guts, and although we have progressed in the analysis of the composition of the microbiota and of the key metabolites it produces, “we still need more work to go beyond the simple associations”, remarks Cani. And he adds, “we need to provide as much as possible more complex analysis if we want to approach causality”.
Simple associations, such as these bacteria are good because they do a certain thing, or they are bad because they are the root of a specific disease, may lead to misinterpretation. Or even worse, the expected results might be oversold when transposed into the human context. New techniques and research will almost certainly shed light on these questions on gut microbiota. And from the Gut Microbiota for Health platform, we will intend to tell you all about them. So, stay tuned!
Cani PD. Human gut microbiome: hopes, threats and promises Gut (BMJ). 2018; doi: 10.1136/gutjnl-2018-316723
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