They confirm the relationship between microbiota and depression

  • Two studies have just been published that conclude that “the gut microbiota may play a key role in depression”

  • They have studied the fecal microbiota of thousands of people and have found a “relationship between the diversity and composition of the microbiota and depressive symptoms”

  • Intestinal bacteria produce substances that can affect the brain: any change in the microbiota produces changes in these substances, affecting our physical and mental health

Microbiota and brain. Microbiologists and neuroscientists are increasingly studying this relationship. “A good microbiota is synonymous with good health”Explain Ignacio López-Goñi, Professor of Microbiology at the University of Navarra. But when talking about health we are not only talking about physics, also of the mental They go together. And it seems increasingly clear that the microbiota plays a key role in both.

The microbiota, or intestinal flora, is the set of living microorganisms or bacteria found in the intestine. A diverse and balanced microbiota (in quantity and type of bacteria) is essential for a healthy and balanced organism. If there is a decompensation, we can get sick. Both physically and mentally. Our microbiota influences our brain activity, our behavior, our emotions.

There is already evidence of the relationship between the microbiota and diseases such as colon cancer or diabetes. But it is also increasingly associated with pathologies such as autism or depression. We know, for example, that “what we think and feel affects the microbiota, and vice versa.” She explained it in NIUS a few days ago Isabel María Martín Monzón, Professor of Psychobiology at the University of Seville.

And now two studies have just been published in Nature Communications that confirm that the diversity of the intestinal microbiota is involved in depression. “The conclusion is that in people with depression there is a change in the microbiota, that is compelling”, affirms López-Goñi. And it is compelling due to the number of cases that have been studied.

Fecal microbiota of 5,000 people

The microbiota-depression relationship has been studied for some time, but until now studies have been carried out with very few samples. “Now The microbiota of almost 5,000 people has been studied, and this has quite strong statistical validity”. New studies confirm that there is an evident relationship between depression and intestinal bacteria. What does that relationship consist of?

In one of the studies, they were able to identify up to thirteen different microbial groups associated with depressive symptoms. “These bacteria are involved in the synthesis of glutamate, butyrate, serotonin, and gamma aminobutyric acid (GABA), which are key neurotransmitters for depression.” They found that certain bacteria are increased, and others decreased, in people with depression. “Our study suggests that the composition of the gut microbiota may play a key role in depression“the authors conclude.

In the other study, researchers have analyzed the fecal microbiota of more than 3,000 people with depression. And they have also done so in people of different ethnicities. Because it is known that “both the microbiome and the degree of depression vary substantially between different ethnic groups.”

They made a genomic map of the microorganisms present in its microbiota, specifically studying bacteria. And they found that there is a relationship between the diversity and composition of the microbiota and depressive symptoms. Regardless of ethnicity. “The results show that the gut microbiota is related to depressive symptoms, and that this association is generalized across all ethnic groups.” But How these intestinal bacteria can affect our mood?

If the microbiota is altered, brain function is altered

“It’s known that many of these bacteria produce substances that are likely to affect the brain”, explains López-Goñi. “Intestinal bacteria produce hormones, long-chain fatty acids, neurotransmitters, serotonin, etc… and all these substances, in some way, can affect brain function.”

Therefore, if this microbiota is altered for any reason (from diet or lifestyle to infection or the use of antibiotics), “Changes in these bacteria produce changes in the substances they produce, and also affect brain function.” We are talking, in this case, about changes in the brain that affect mental health.

“We have more and more data that our biology and physiology (how we function) also depend on these microorganisms, not only at the intestinal level but throughout the body,” warns the Navarrese microbiologist. He explains that, just like in nature, “Human beings are also an ecosystem with millions of cells and millions of microorganisms. If it is balanced it works well, but if there is a change, alterations occur”. This is what scientists call “dysbiosis”: the alteration in the number or diversity of these microorganisms.

the psychobiologist Martin Monzon explains something similar. “Inside and on us live from 10 to 100 trillion microorganisms, with which we maintain a symbiotic relationship. With such a figure, it is not surprising that its existence even affects how we think, feel or get sick”.

Is the microbiota cause or consequence?

There is an important nuance to all of this. López-Goñi warns. “We do not know if depression is what causes the change in the microbiota or if it is the other way around. There is a very clear relationship between the microbiota and depression, but we do not know if it is cause or effect”. Changes in the microbiota, alterations in its composition or its diversity, are they the cause or consequence of depression? That is, warns the scientist, “the great unknown” that remains unresolved.

Doing so is not easy, because it would require a very long follow-up of people without depression, to see if they develop it or not. But knowing that there is a relationship between the two is important, because it opens up another key question. If there is an alteration of the microbiota in depression, would there be any way to promote or restore that balance in the microorganisms of the intestine?in order to also improve that depression?

Manipulate the microbiota

At the moment, López-Goñi says no. If we talk about “manipulating the microbiota”, he says, “we are in the stone age”. He assures that, from a theoretical point of view, it makes sense, but from a practical point of view it is not yet feasible. “The problem with probiotics is that we don’t know exactly what type of bacteria should be added, because it depends a lot on what your microbiota is like. In the future we will have to go to personalized probiotics“, Explain. But there’s plenty of time left for that, she warns.

The Scientists already know “many of the bacteria that are altered in depression”, but knowing them is not enough to be able to intervene in some way. “We know they are there, but we are not yet able to cultivate them., nor to prepare kilos and kilos of this bacterium in the laboratory. We do not have the means for it ”, settles the microbiologist.

What does seem clear and proven is that a balanced microbiota “is key to physical and mental health”. And knowing it implies “a paradigm shift in personalized medicine.”

A good diet, waiting for drugs and transplants

“In the near future, it is aspired that the modulation of bacteria (through fecal transplants, nutrition, etc.) be one of the coadjuvant strategies for the treatment of brain cancer, together with neurosurgery, chemotherapy and the use of other drugs”, says Isabel María Martín Monzón. Recently, in fact, we told you about the first drug based on fecal microbiota, and about The therapeutic avenues that open up with fecal transplants and autotransplants.

But both the microbiologist and the psychobiologist They have a lot to do with diet. whose relationship with mental health, not only physical, is becoming clearer. “The evidence suggests that the Mediterranean diet can be an effective complementary treatment for pathologies such as depression, partly due to the way in which our microbiota changes, increasing microbes that promote health (eg, F. prausnitzii, Bifidobacterium spp.)”, explains Martín Monzón. “Recent studies have identified that some probiotics, such as Lactobacillus and Bifidobacterium strains, may reduce the severity of depressive symptoms (compared to placebo) when taken for several weeks.

“A diverse and numerous microbiota is a sign of health, of good physical and mental health. Y what will generate it the most for you”, explains López-Goñi, is “a varied and balanced diet”.

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