We have long known that there is more to us than just us. A colony of billions of microorganisms inside us conditions our existence. Popular wisdom says that to be slim you just need more soles and less pot, but the reality is much more complicated and perhaps it’s because of these little insects that live in us. Studies show that exercise does not help with weight loss, and scientists struggle to explain the reasons for the obesity epidemic, which has doubled in many countries since 1980.
In recent years, the study of the complex relationship between our food and the bacteria present in the body has begun to provide answers to these unknowns. To advance knowledge of the relationships between the microbiome and diseases such as cardiovascular disease or cancer, the collaboration of computer scientists, experimental biologists, statisticians or clinicians is necessary to link the enormous amounts of information provided by sequencing techniques in order to transform them into tools that improve health.
One of the leaders of this scientific revolution is Nicola Segata (Trento, Italy, 43 years old). In 2013, he founded a laboratory at the University of Trento that brings together scientists from all these specialties to study the diversity of the human microbiome and its role in human diseases. He has just published an article in the magazine Nature in which, in collaboration with an international group of scientists, data from 34,000 people is analyzed to create the most detailed map to date of the relationships between diet, the microbes in our gut and health.
After classifying hundreds of bacterial species according to their association with health markers such as body mass index or glucose level, the researchers found that people furthest from obesity or without metabolic diseases had more favorable bacterial species and fewer unfavorable species, and that it was possible to carry out dietary interventions to improve this composition. Furthermore, they found that many of these “good” bacteria have not yet been named or cultured, revealing how much remains to be known and the potential to base true precision nutrition on this science.
Ask. In their latest work, they found that there is still much to know about the bacterial ecosystems of our gut, but that many products are already sold based on knowledge of the microbiome. Do we know enough to use the microbiome in medicine?
Answer. Yes, I think the field has gotten much better at understanding the composition and function of the microbiome, even though there is much that remains unknown. Each of us carries within us completely unknown species of microbes, and even for the species of which we know something, at least the name or certain functions, most of the functions remain unknown. But we don’t need to understand everything to use the microbiome clinically, because even in medicine there are many effective treatments and, at least initially, we didn’t know why they worked. An example in this area is the transplantation of fecal microbes, which works very well for certain diseases, although we do not know the exact mechanism by which they work.
Q. They found that people with more harmful bacteria had a higher body mass index. But what comes first?
A. We are a complex system made up of both our cells and our microbiome. And diet acts on both at the same time, so sometimes we cannot separate cause and effect, we only see an association. One case in which it is possible to separate it is an article we published with Francesco Asnicar on coffee and the abundance of a bacteria in the intestine called Lawsonibacter asaccharolyticus. We know it’s not just an association because when we grow the microbe in vitro, it grows much better if we add coffee. But coffee is a special food, because you can drink it three times a day or not at all, and it is very special. Most of the time, it is impossible to disentangle cause and effect.
Q. Are there times when certain foods are good, but are associated with harmful bacteria?
A. First of all, it seems that there is no universally good diet, at least from a microbiota perspective. The same diet can impact different individuals differently because each of us’ microbiota is very different and the microbiota influences how we process food. Additionally, there are many bacteria that may be beneficial in some individuals and less effective in others. Because they are different individuals, but also because there are variants of the same species.
Q. Will this type of research be used to personalize diets?
A. The idea is to move towards personalized nutrition, because different foods will have a different effect on different microbiota. The goal is to understand which foods change the microbiome in the right way for you. But I have to say two things. First, it only has an impact if your baseline diet is already relatively good. If we compare someone who eats fast food every day with someone who eats a good diet, the first person’s problem is not personalization. But between two good diets, the difference can be made thanks to personalization.
Q. Can probiotics be helpful in improving our microbiome and health?
A. There are two different things. One thing is prebiotics, fiber or other compounds that can modify the microbiota, and another is probiotics, living organisms that, in theory, could colonize our gut. Both approaches can modify the microbiota, the difficult part is knowing which of these interventions will be successful and bring about the desired changes. There are probiotics that do not survive in our gut and other new generation probiotics that can. I’m not saying it can’t work, but we should think of them as supplements that would work for some people and not others, just like some foods work better for some people than others. It will probably be easier to modify the microbiota from prebiotics or foods, also from a regulatory point of view, because the probiotics that have the highest chance of success are the new generation or the bacteria already present in people’s bodies, but it is difficult to introduce them to other people. We need to be able to grow and produce these microbes and make sure they’re not bad. In contrast, many of the prebiotics found in foods, such as dairy products, are not problematic, although their effect may be minor.
Q. He has done work showing that part of the composition of our microbiome depends on the people we interact with. Does improving our intestinal microbiota depend on individual decisions or does it require policies acting at the population level? I don’t know if you can change your microbiota if all your friends or family don’t do it.
A. Microbes are living organisms that are not generated in our body, they come from somewhere. Just as we transmit pathogens, we transmit good bacteria. If we go to the extreme, we could say that you should choose your partners based on the microbiota that they can transmit to you, but that doesn’t make much sense.
Microbes also come from food. Fermented products contain a lot of microbes, vegetables less, and when we eat these products we also ingest the bacteria or fungi they contain and some of them have an impact on our intestine. We have mapped the composition of the food microbiome and there is overlap with the gut microbiome. However, most microbes do not come from food.
Q. In other work, he has also found that non-communicable diseases, such as cancer or diabetes, are, to some extent, transmissible through the microbiome.
A. Yes, this can also be somewhat the case with obesity. But when we talk about this article, the effect of diet on the microbiota is something that we have quantified and it is much greater than that of our social interactions on the risk of developing diabetes or becoming obese. Certain bacteria transmitted to us from other individuals can increase the risk of metabolic diseases, but the main risk factors come from our diet and the interactions within each individual between diet and microbiome.
Q. Have you noticed any non-intuitive effects of these relationships between diet and the microbiome?
A. We have seen that the dietary aspect that has the most positive impact on our microbiota is the diversity of the foods we consume. It’s not necessarily the amount of each healthy vegetable; Rather, it’s about how many different types of healthy vegetables we eat each day. It is more important to eat a few different healthy vegetables than to eat a lot, one or two. Indeed, even good foods have different effects on different microbiota and we want a diversity of healthy microbes, not just a few.
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