Gabriel Núñez: “Take a yogurt if you like it but don’t expect great probiotic benefits”

Did you always want to study bacteria?

No, no, at all. Initially I focused on immunology, cancer and then in innate immunity and microbiology. As the pathology of inflammatory diseases is closely related to innate immunity and infections, entering the study of microbiota was something natural. I started working in microbiota around 2008-2009.

His research studies the relationship between microbiota and inflammatory and autoimmune diseases.

The microbiota is a complex system. From the numerical point of view, the number of bacteria that make up our microbiota is greater than that of our own somatic cells. In fact, in terms of quantity, we could say that we are more bacteria than humans. The same happens at the genetic level, since the microbiota genes exceed those of our own genome. It is clear that some diseases are caused directly by the microbiota. There are people who die from infections caused by microorganisms that were already within their body. A clear example is sepsis: when a bacterium reaches the bloodstream and causes septic shock, it is often not a bacterium acquired in the hospital, but one that already lived in the patient’s body.

There are other diseases, such as ulcerative colitis and Crohn’s disease, which have an important genetic component, but in which certain intestine microorganisms also play a role. In these cases, we know that microbiota is a necessary factor for the development of the disease.

Then, there are many other pathologies in which it is suspected that the microbiota has an influence, although it is not clear to what extent. For example, in atherosclerosis, it has been identified that certain metabolites caused by bacteria can promote the development of the disease. However, we do not know if atherosclerosis would occur in the same way without the presence of these bacteria or if their influence accelerates the process.

The list of diseases in which it is believed that the microbiota has a paper is increasingly wide. Its possible relationship with autism, liver diseases and many other conditions have been studied. However, most studies have been carried out in animal models, so it is not yet clear if the effects are the same in humans. What we do know with certainty is that, in diseases such as sepsis or septic shock, the bacteria that causes the disease comes from the patient himself and, in some cases, it can be lethal.

How can we help improve our microbiota?

We all have a unique and different microbiota. The colonization of the microbiota begins immediately after birth, influenced by the mother, physical contact with her, the hospital environment, doctors and nurses. From that moment, the digestive tract and the skin begin to populate with microorganisms. However, most of the microbiota is found in the intestine, since there are more nutrients available. In the skin, on the other hand, the amount of bacteria is lower because there are fewer food sources.

Nutrition plays a fundamental role in the microbiota. The diet can modify its composition drastically in just 48 hours. For example, a meat rich in meat or a vegan diet generates significant changes in the intestinal microbiota. Many bacteria depend on the vegetable fiber to survive. Although our body cannot digest the fiber, it reaches the colon, where certain bacteria ferment and produce beneficial health compounds.

This relationship between the human body and the microbiota is known as mutualism: we provide food and a stable environment for these microorganisms, and they, in return, offer us metabolic benefits, protection against infectious diseases and other essential functions. It is a balance in which both parties benefit.

And in addition to the diet?

The microbiota can be modified in various ways, but some are more efficient than others. The diet is a key factor that can alter it significantly. However, another element that deeply influences its composition is the use of antibiotics. When we take antibiotics, we eliminate certain bacteria sensitive to them, which temporarily changes the microbiota. Although when the treatment suspends many of these bacteria can re -colonize the intestine, there is always a reservoir of resistant microorganisms that survives and contributes to its recovery.

The use of antibiotics in childhood is a very important issue. There is evidence that its frequent administration in the first years of life can be related to an increased risk of developing allergies and other diseases in adulthood. For this reason, it is recommended to use antibiotics only when strictly necessary, not only to avoid bacterial resistance, but also to minimize possible long -term effects on microbiota and health in general.

Probiotics, prebiotics …

Probiotics contain live microorganisms, such as those found in yogurt. However, it is not clear that its consumption has a significant impact on the intestinal microbiota. When we ingest these microorganisms, they do not remain in the digestive system, since they are naturally eliminated. Therefore, I always say: “Take the yogurt if you like it, because it is a healthy food, but do not expect great probiotic benefits.” Until now, there are no conclusive studies that demonstrate that the consumption of yogurt or other probiotics significantly alters the microbiota, partly because it is very difficult to design studies that prove it with certainty.

However, in some diseases, effective treatments based on the microbiota have been found. A specific case is pseudomembranous colitis, a serious infection caused by difficile clostrides, a bacterium that releases toxins and causes severe intestinal inflammation. This disease usually appears when the prolonged use of antibiotics reduces the diversity of intestinal microbiota, allowing proliferating pathogenic bacteria without control.

In these cases, fecal microbiota transplants have proven to be a highly effective and economical treatment. They consist of transferring complete intestinal microbiota of a healthy donor to a patient, restoring bacterial balance in his intestine. In the US, the material usually comes from relatives, while donors are medically evaluated in Europe to ensure that they do not carry pathogens.

Previously, this procedure was carried out rudimentaryly, managing the microbiota directly by probes. Today, there are white capsules specially designed to contain the necessary bacteria, doing the most accessible treatment.

It is shown that populations that live in more isolated environments, such as indigenous communities in the jungle, have a much more diverse microbiota than industrialized zones populations.

Yes, exactly. They have greater microbial diversity and species of bacteria that we no longer have. It is believed that some of these bacteria were part of the human microbiota in the past, but that have been lost with changes in food and modern lifestyle. The diet plays a fundamental role in this difference.

Are there microbiota banks that seek to preserve these bacteria before they disappear over time?

Yes, there are initiatives to isolate and conserve microbiotas of indigenous communities, such as those of Colombia, Peru or Brazil, because these populations have a microbiota very different from ours. In large part, this is due to its diet, which differs from the western diet.

And if someone lived with them for a long time, could you acquire part of their microbiota?

I don’t know if there are specific studies on that, but it’s likely. There is evidence that bacteria can be transferred between people who live, for example, between brothers. Although each person has their own microbiota, that of the brothers is usually more similar to each other than that of unrelated individuals, although not identical.

Is there a “ideal” microbiota?

There is no unique and perfect microbiota, but it is known that certain groups of bacteria can protect us against some diseases. For example, there are populations of bacteria that help prevent infections on the oral path. However, we still do not fully understand how exactly the species responsible for this protection are.

Could that knowledge be used to develop protective strategies?

It is not yet clear. The human microbiota is incredibly diverse; It is estimated that each person houses between 500 and 1,000 different bacterial species. This variability makes it difficult to identify an “ideal” microbiota applicable to all.

He has been in the US for more than 45 years, has the return to Spain ever raised?

No, what happens is that we all go through a crisis, an existential crisis. The majority of those who emigrate do so for economic reasons. Many think that, upon reaching another country, they will become rich, but the reality is different. Return? No. Actually, that is a myth, because it almost never happens. Very few people return with great fortunes, such as the so -called “Indian” that bought houses in Asturias; That percentage is minimal, most stay.

In my case, when I left, it was not for an economic issue, but for interest in training as a researcher. It was a personal choice. The existential crisis may appear after five or ten years, when you realize that you have settled and that, probably, you will not return. Then the question arises: do I really want to live here or not?

I did not have a strong connection with Spain at that time. Yes, I had family in Seville, but it wasn’t about that. The question was to decide where I wanted to live: in this country, in the United States or elsewhere. And the time comes when you have to make a decision, especially when you finish your training and you must look for a stable job with a projection of the future. Sometimes you spend a year going around, exploring alternatives, asking you if it is the right way. But there comes a point where you have it clear and simply go ahead.

Research lives convulsive times in the USA How does this situation affect your work?

For the Academy and for researchers who are part of it, recent changes have been quite radical. We still do not know how they will be reflected. There are rumors about a possible cut in the science budget and the elimination of some issues, but there is still no definitive information. Many projects are paralyzed and the future of financing remains uncertain, which has generated great concern among academics. For example, one of the approved cuts affects the so -called “overhead” (indirect expenses). Before, if $ 100,000 were granted for investigation, an additional percentage was added to cover these costs, which varied between 30%and 70%, depending on the institution (for example, Harvard reached 70%). Now, this percentage has been reduced to 15% in a general way. This cut represents a significant decrease in the available funds.