The human body is an intricate and complex system made up of trillions of cells, each with its own specific function. While the importance of organs such as the heart, lungs, and brain is well known, a relatively new area of research has shed light on the significance of the gut microbiome (or the gut flora).

“It’s a vital organ in your body and you need to look after it. If you do that, it will look after you,” says Professor Tim Spector, an epidemiologist at King’s College London, author of two books on dietary and gut health.

The gut flora is the collection of microorganisms that live in our digestive tract. These tiny bacteria, fungi, and viruses, were traditionally disregarded and ignored. However, in recent years, scientists have discovered that they can play a critical role in maintaining our overall health and well-being.

From aiding in digestion to regulating our immune system and even impacting our mood and behavior, the gut microbiome has become a hot topic of study in the world of science. In this article, we will delve into the fascinating world of gut flora, exploring its function, diversity, and potential implications for human health.

Psychobiome, probiotics, psychobiotics

In the past couple of decades, we’ve witnessed a paradigm shift in our understanding of the brain. We’re still nowhere near unraveling the intricacies of this organ, but researchers are taking major strides toward this goal.

While much progress has been made in understanding the inner workings of our brains, a relatively new area of research has recently emerged. This area suggested that the brain may be actively influenced by external factors. In particular, something that’s in your gut.

The “psychobiome” is increasingly being used to refer to the complex and dynamic interplay between our gut microbiome and our central nervous system. Recent research has found that gut flora can influence our mood, behavior, and even our cognitive function. From depression and anxiety to autism and schizophrenia, as well as all sorts of health conditions, the psychobiome also seems to be linked to health problems.

With growing interest in the role of the gut microbiome in human health, probiotics have also become an increasingly popular tool. Probiotics, live microorganisms, are used for both prevention and treatment of a range of health conditions.

While probiotics have been used for centuries in the form of fermented foods such as yogurt, kefir, and sauerkraut, advances in technology have allowed for the development of more targeted and effective probiotic supplements.

Research has shown that probiotics can have a positive impact on a range of health conditions, from digestive disorders to allergies and even mental health. Probiotics work by modulating the gut microbiome, promoting the growth of beneficial bacteria and inhibiting the growth of harmful bacteria.

“The right types of bacteria promote healthy metabolism and diminish inflammation, which can harm our health,” says Endocrinologist Katherine Samaras, Professor of Medicine at UNSW and a clinical fellow at the Garvan Institute of Medical Research in Sydney.

“The wrong types of bacteria cause systemic inflammation, which damages our arteries, promotes diabetes and fatty liver disease, and is considered to contribute to accelerated ageing, including cognitive [brain function] decline.”

Because gut flora affects the brain so much, the field of psychobiotics (probiotics that influence bacteria–brain relationships) has also emerged.

Basically, psychobiotics is the love child of psychology and probiotics. This field of science revolves around probiotics or prebiotics which when ingested have an impact on our mental state due to their interaction with the gut microbiome. 

These fields are still in the early days, but early results are promising, particularly as we’re starting to understand more about gut flora itself.

What is gut flora made of

The composition of the gut flora can vary depending on various factors such as diet, age, genetics, and lifestyle. Some conditions can also change its composition.

However, our gut is dominated by a few thousand species of microbes that include bacteria, fungi, viruses, and archaea. All in all, these microscopic organisms weigh about 2 kilograms which is more than the 1.4-kilogram human brain.

Still, some groups are more dominant in general over the human microbiome. These six groups of microorganisms make out some 90% of gut microbiota:

1. Bacteroidetes: This is a large and diverse group of bacteria that play a crucial role in breaking down complex proteins or complex sugar polymers into things we can digest more easily.
2. Firmicutes: This is another large group of bacteria that includes species such as Lactobacillus (which ferments yogurt) and Clostridium (which is one of the common causes of food poisoning). Firmicutes are involved in various metabolic processes. They also produce an important substance, butyrate, that keeps the colon healthy.
3. Actinobacteria: This group of bacteria includes species such as Bifidobacterium. This group is known for its probiotic properties and its ability to promote gut health.
4. Proteobacteria: This group of bacteria includes species such as Escherichia coli and Salmonella, which are often associated with infections and inflammation in the gut.
5. Verrucomicrobia: This is a relatively small group of bacteria that includes the species Akkermansia muciniphila, which has been linked to various health benefits, including improved metabolic health and reduced inflammation.
6. Fusobacteria: while some species of Fusobacteria have been linked to infections, recent research has shown that certain strains may have a beneficial role in the gut microbiome by producing butyrate, a short-chain fatty acid that promotes gut health.

All these types of gut bacteria (and the less common ones) affect various vital processes from being able to program the developing immune system, helping the body manufacture nutrients, and defending against infection, to producing neurochemicals essential for brain function.

In fact, the gut flora is so important that it’s often considered our body’s “second brain.”

The vagus nerve: how are the brain and the gut connected? We asked the experts

Studies have shown that gut microbiota can communicate with the central nervous system via the gut-brain axis. This hypothesized axis entails that there is a two-way relationship between the gut and brain, and this affects our health and behavior. 

The vagus nerve is the main wire that connects the brain and digestive tract and is made up of 500 million neurons. Being the main nerve in the parasympathetic nervous system, the vagus nerve plays a key role in mood regulation, heart rate, digestion and immunity.

A 2014 study published in PLOS One found that psychological stress impacts the vagus nerve which could be involved in the development of gastrointestinal disorders particularly irritable bowel syndrome and inflammatory bowel disease. 

In another study, headed by Jeroen Raes of the Catholic University of Leuven, where they analyzed 1,000 health records of one Belgian and one Dutch groups, it was revealed that people with depression had deficits of two bacterial species (Coprococcus and Dialister) regardless of antidepressant treatment.

Professor Raes: “This study provides further evidence that Bacteroides2 may have a negative impact. Microbial communities linked to intestinal disease appear to share certain features with those linked to reduced mental health.”

“Many substances that may influence the brain and the nervous system are produced in our gut,” doctoral student Mireia Vallès-Colomer continues.

“We wanted to find out which microorganisms might be involved in this process. Our toolbox makes it possible to identify bacteria that may have an impact on our mental health and to unravel the underlying mechanism. For one thing, we found that the ability of microorganisms to produce DOPAC – a substance linked to the neurotransmitter dopamine – is associated with a better mental quality of life.”

This further provides evidence that a wide range of gut bacteria can produce neuroactive compounds and the wrong mixture of microbes can derail the process.

Furthermore, microbe products influence our body’s enteroendocrine cells, found in the lining of the gut, which participate in releasing hormones and other peptides that aid in regulating digestion, controlling insulin levels, and producing the neurotransmitter serotonin, a natural mood booster. 

Animal studies using model organisms also produced promising results. Researchers investigated the impacts of the bacterial strain Lactobacills rhamnosus on anxiety and cognitive function in mice. Interestingly, the group who took the probiotic supplement had reduced levels of anxiety and better cognitive activity than those who were not given the treatment.

The team believes that bacteria affect Gamma-aminobutyric acid (GABA) production, a neurotransmitter involved in anxiety and depression. However, scientists have cautioned that this study still lacks certainty and needs further development before going to human clinical trials. Generally, gut-brain communication has been mostly explored in animal models and human research still lags behind, highlighting that this field is still yet to be fully understood. 

Not a cure-all for psychological and mental issues

While the potential benefits of psychobiotics are indeed promising, they should not be regarded as a cure-all for anyone’s mental problem as per gastroenterologist Avanish Aggarwal, M.D., and nutritional psychiatrist Uma Naidoo, M.D. in their Forbes interview.

“There’s a lot of neural activity in the gut, including serotonin, dopamine and GABA,” says Dr. Aggarwal, referring to three neurotransmitters that are central to mental health, including anxiety and depression. “The gut produces more than 90% of the body’s serotonin,” he adds.

Moreover, everyone must be wary that not all strains of bacteria have the same effects on our cognitive function and optimal dosage is still being studied. As experts are still trying to figure out where psychobiotics fit in the gut-brain connection, there are still ways to incorporate them into your life such as incorporating probiotic supplements and fermented foods into your diet.

Some examples of these foods that have good and beneficial live organisms are kefir, yogurt, kimchi and pickled vegetables. Alongside a healthy diet, it is also best to have good quality sleep, lessen stress and exercise regularly to help maintain good and stable mental health. 

Psychobiotics could be the future of treating mental health conditions and improving cognitive function. As it is gaining momentum now more than ever, we are likely going to be able to harness the full potential of our gut microbiome for treating and supporting mental health. 

However, the benefits of probiotics are sometimes exaggerated, and the same thing may start to happen in the field of psychobiotics. It’s important to follow science-based evidence and not just jump on the hype of a new class of treatments — as promising as they may be.

How to restore healthy gut flora

There are several ways to improve gut flora, including:

1. Eat a healthy, balanced diet with plenty of fiber-rich foods, such as fruits, vegetables, legumes, and whole grains.
2. Incorporate fermented foods into your diet, such as yogurt, kefir, sauerkraut, kimchi, kombucha, and miso.
3. Limit intake of processed foods, added sugars, and saturated fats.
4. Stay hydrated by drinking plenty of water and other fluids.
5. Manage stress levels through meditation, yoga, exercise, or other relaxation techniques.
6. Avoid unnecessary use of antibiotics, as they can disrupt the balance of gut bacteria.
7. Consider taking probiotic supplements, which contain live bacteria that can help improve gut health.
8. Eat prebiotic foods, such as garlic, onions, bananas, asparagus, and artichokes, which can help feed the beneficial bacteria in the gut.
9. Get enough sleep, as sleep deprivation can negatively impact gut health.
10. Avoid smoking and excessive alcohol consumption, as they can harm gut bacteria and overall health.
11. Consider working with a registered dietitian or healthcare provider to develop a personalized plan to improve gut health.
12. Incorporate regular exercise into your routine, as it can help promote a healthy gut microbiome.
13. Try to eat a variety of foods to ensure a diverse microbiome.

The bottom line

The emerging research on the microbiome and the gut-brain connection has opened up exciting new avenues for understanding the human body and the factors that influence our health and well-being. While much more research is needed to fully understand the complex interactions between the gut microbiome and the brain, the evidence so far suggests that a healthy gut may be key to a healthy mind.

By taking care of our gut microbiome through a healthy diet, exercise, and other lifestyle factors, we may be able to support not only our physical health but also our mental health and cognitive function. As we continue to uncover the intricacies of the microbiome and its impact on human health, the possibilities for new treatments and interventions are truly limitless.

The future of medicine and human health is indeed exciting, and the study of the microbiome is sure to play a major role in shaping it.