The food and science supplement of the newspaper El Confidencial, Alimente, has dedicated a space to talk about the microbiota.
In order to do so, it has had the collaboration of the expert doctor Yolanda Sanz, from the Microbial Ecology, Nutrition and Health group of the Institute of Agrochemistry and Food Technology. She has been the coordinator of the recently completed European project MyNewGut, in which, for five years, some thirty research groups from 15 countries have worked to unravel the relationship between the intestinal microbiota and its genome -the microbioma- in the development of obesity and behavioural disorders linked to our lifestyle.
One of the new approaches is that of the role played by the microbiota: how our bacteria influence whether we lose or gain more or less weight, but also whether our mood - more anxiety, more depression - associated with obesity is altered. Or, for example, how the type of diet we follow - more or less rich in protein, fat or fibre - will influence our microbiota to produce toxic substances that can harm our health or beneficial substances that protect us from illness.
The scientists of the European MyNewGut project know a great deal about all this. For five years, around thirty research groups from 15 countries have worked to unravel the relationship between the intestinal microbiota and its genome - the microbiome - in the development of obesity and behavioural disorders linked to our lifestyle. The vision, says the Spanish Yolanda Sanz, researcher at IATA-CSIC and coordinator of the project, has been multidisciplinary: "Experts in microbiology and microbioma, physiology, immunology, psychiatry and nutrition have researched and worked together with the idea of evaluating how diet can influence the microbiota and thus modify our metabolic and mental health. The aim is to prevent not only obesity, but also associated pathologies such as the metabolic syndrome leading to diabetes or cardiovascular disease and mood disorders.
Bacteria for weight loss?
One of MyNewGut's strategies has been to go beyond the classic probiotics - i.e. lactobacilli and bifidobacteria - and isolate 'new' bacteria. We had no doubt that there had to be many other bacteria that could potentially be beneficial, but whose function we don't yet know," explains Yolanda Sanz. So we set out to explore other microorganisms that were unknown to us and, among them, we isolated Bacteroides uniformis, a bacterium that is patented for use in obesity.
What is known about this bacteroid? "We have seen, in animal models, that its capacity to reduce obesity is greater than that of conventional probiotics, probably due to an immunoregulatory mechanism: it reduces inflammation and this would stop the cascade of subsequent events that lead to the development of insulin resistance and, for example, diabetes".
There is another very interesting bacterium: Bifidobacterium pseudocatenulatum, which has been found to "reduce weight, modify blood lipids favourably, improve oral glucose tolerance and have an effect on obesity. But even more novel is its effect on mood, specifically the depression associated with obesity. See below.
Diets high in fat, obesity and depression
We have a mouse. We give him a diet rich in saturated fats, we induce obesity and we see that the mouse develops depressive symptoms. However, if we then administer the bifidobacteria we talked about earlier, those depression symptoms are reduced. So, in a very summarized way, we can explain one of the findings of MyNewGut.
"There are quite robust epidemiological data, the result of the accumulation of many studies, which show that obesity and associated comorbidities are associated with an increased risk of developing depression. And depression, in turn, increases the risk of developing a cardiovascular event, as well as other metabolic pathologies associated with obesity. We already knew this; the interesting thing is the next step, the fact that this bifidobacteria can reverse the process. "We have seen that, on the one hand, it seems to reduce intestinal inflammation, and consequently also systemic and cerebral inflammation. That way, serotonin levels are restored both in the gut and in the hippocampus, one of the brain areas affected in the context of depression. And what could its clinical usefulness be? "We thought some bacteria might help relieve the symptoms of obesity-associated depression.
Hyperprotein Diets
We all know about very protein-rich diets and we know that they are always in the spotlight and heavily questioned for their possible long-term adverse effects. We have often heard that excess protein could damage some tissues, but we did not know that it could be due to the substances made by bacteria (metabolites).
"It is true that hyperproteic diets have the advantage that at the metabolic level they help us maintain body weight; however, on the other hand, they also increase the amount of protein that reaches the large intestine; and that protein is metabolised by bacteria, which can generate possible compounds with toxic, cytotoxic properties for the body's cells and also for other organs".
What have the MyNewGut researchers discovered? First, that "the concentration of proteins causes the microbiota to generate more toxic metabolites. And a fundamental finding has been to see that not only the concentration of proteins influences, but also their origin. Our results suggest that when proteins are of plant origin, the number of toxic metabolites is reduced.
From here, the conclusion is that "we must be cautious when recommending diets high in proteins to regulate body weight, especially if it is done for a very long time and recurrently. It is true that obesity is a major problem and it is possible that at some point it is strictly necessary for the patient to lose weight in a relatively short time, but care must be taken when maintaining a diet of this type over time.
The possible health problems, he says, are not negligible: "We have seen that, when faced with a hyperproteic diet, intestinal bacteria produce cytotoxic metabolites for the cells of the intestinal epithelium, which could cause colorectal cancer in the long term. We have also observed that other toxins appear in urine that could be related to kidney diseases.
What about the future?
There are so many unanswered questions. "And as we learn and discover things, we realize all that remains to be known," acknowledges Yolanda Sanz, who is clear, at least, that the approach to obesity is changing and many other factors involved in its development have to be taken into account. "We really need nutrition and medicine to go hand in hand, for there to be greater integration of nutrition in health care. And, of course, we have to incorporate new elements, such as the function of the microbiota and products derived from the microbiome. We have to develop other strategies, such as the identification of bacteria or bioactive metabolites, to produce them with all the guarantees in laboratory conditions and use them as probiotics. They are alternatives for the future that will have to be incorporated into the care and maintenance of health, as well as diet, physical exercise and, in some cases, certain drugs.