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Gut Health and Mental Health

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People are more aware of their gut health than ever before. What is the impact of your gut health on your overall well-being? How does your gut health influence your mental health? What do we know and not know about gut health and how it shapes overall health? What can you do to improve your gut health?

Most of us think of ourselves as a single living entity. In fact, each of us is made up of trillions of living organisms. There are more helpful bacteria than the number of cells in your body. The term used to describe the vast array of bacteria, viruses, phages, fungi, etcetera is “gut microbiome.” To be fair, no one has counted them one by one, but the estimates seem pretty reasonable based on how many are found in any given area of the gut.

Phages, or bacteriophages, to give them their full name, are viruses that attack only bacteria. There are more phages on the planet than all other living entities combined. Phages are part of what is known as the virome (a subset of the gut biome), the viruses that live in our gut. Our gut virome has two major elements: eukaryotic viruses, which replicate in our cells, and bacteriophages in gut bacteria. They make up by far the largest number in the community of life in our gut.

We live in a symbiotic relationship with our gut microbiome. We give trillions of living entities a home. They help us digest food and turn it into nutritious components that keep us healthy. A healthy host is also good for our trillions of microscopic friends.

If we keep them well-fed, they multiply and reproduce at such a rate that the “bad bacteria” can’t get a foothold; they are soldiers protecting us from harm.

When there are too many bad bacteria or phages that attack the good bacteria, we are more prone to diseases such as IBS (irritable bowel syndrome), ulcerative colitis, and heart disease, to name but a few. Meat enables the bad bacteria to cause the liver to produce trimethylamine-N-oxide. We don’t understand the linkages, but the evidence of raised cholesterol being associated with trimethylamine-N-oxide (TMAO), is pretty strong.

Helpfully, in extra virgin olive oil, there is 3,3-dimethyl-1-butanol (DMB), which seems to enable the blocking of TMAO. Kidney disease also seems to involve TMAO, but there, too, the full processes by which TMAO causes and mediates illness are not known.

IBS and kidney disease are just two examples of how little we know about the chemical workings of our bodies. The list of diseases that seem to be caused or worsened by an imbalance of gut bacteria is growing as we learn more about the microscopic universe within that keeps us alive.

We are still discovering bacteria and phages, which are new to us, but billions of years old. We are woefully ignorant of metagenomics (the genetics of any microbial ecosystem), which is hardly surprising given that there are so many different varieties.

The holes in our knowledge are huge: our genetics cannot explain over 90% of our biology. The challenge is even larger: there is huge variation between the microbiome of any two people. That in turn may explain why a drug that is designed to save lives can do so for some, and yet causes dangerous side-effects or kills others.

To advance in any field, becoming aware of our ignorance is the first step. Researchers are increasingly aware of the scale of our ignorance about how our own biology works and how it impacts our mental and physical well-being.

Much of the research into understanding the workings of the gut biome is driven by exploring what logically could be happening. For example, suppose you were an engineer seeking to, in principle, design the human body with no knowledge of biology or chemistry. In that case, you may want each system to speak to the other system.

You would want the brain to receive signals from every system, including the gut biome, and for the gut biome to receive signals from the brain. Closed feedback loops must exist all over the body, although we have, currently, at best, a rudimentary understanding of them. Many closed feedback systems must be in place, but we have yet to discover them.

For many years it has been suspected the gut microbiome plays a role in many apparent brain-centred disorders, such as anxiety, depression, autism, schizophrenia, bipolar disorder, Alzheimer’s disease, dementia, and many others. If there are such biome-based causes, how any such processes work, we don’t understand, but we, as a society, are researching.

Here are some fundamentals of what we have discovered so far. Our mental and physical health are both dependent on biochemical neurotransmitters. They are essential for our nervous system to work. They are involved in every system in the body and brain.

So far, we have discovered that glutamate, GABA, serotonin, dopamine, and around 30 others are produced in the gut. Most of the production of the elements of our immune system comes from activity in our microbiome. This next finding might be hugely significant for mental health: 90% of the body’s “happy hormone,” serotonin, is manufactured in our guts.

What could that mean? That we may have been looking in the wrong place for the cause of many mental health problems. Currently, we don’t know enough about the effect of the microbiome on the brain to know what percentage of mental health problems are caused by dysbiosis (biome imbalance). Maybe we have not been looking in the wrong place but have been missing a contributory factor. Perhaps there is a more systemic and wholistic explanation for mental ill health, and the gut biome plays a vital, but not exclusively, causal part.

It is possible that the reason we are seeing such alarming increases in so many diseases and disorders (from obesity through diabetes to Alzheimer’s and beyond, including all immune system-mediated diseases, for example, asthma) is that we are too hygienic. For instance, we know that when very young children are needlessly protected from, say, nuts for fear that they will develop a nut allergy, the opposite happens: they are more likely to become allergic.

In this instance, what is known as ‘the hygiene hypothesis’ seems to be correct; preventing exposure to potentially harmful substances makes it more likely those ‘protected’ will be harmed. Is that because the microbiome has its natural development impaired? That seems likely, but we are not yet at the point where we can demonstrate that lack of exposure to substances automatically makes the body less able to deal with them.

More recently, the related ‘old friends hypothesis’ advocates that modern life prevents people from acquiring the healthy bacteria essential to health. Here, too, we at not at the point where we can say the absence of which bacteria, acquired in which order, at which stage in early life, is harmful to us.

It is highly likely that many of the nearly 100,000 man-made chemicals that we can be exposed to (by breathing, through our skin, and ingesting) are having a deleterious effect on our microbiome.

That would seem likely since most man-made chemicals have never been tested to determine their effects on our microbiome. If, as is widely suspected, many such chemicals are biome impeders, that would explain the substantial rise in immune system-mediated diseases. To elaborate, the immune system’s engine, the microbiome, may be compromised by chemicals not toxic enough to kill us but lethal to vital parts of our microbiome.

Perhaps, in the distant future, we will understand the factors that need to be in play to cause any given mental illness biomedically. If dysbiosis is a major cause of some mental illness, before we can offer any effective treatment, we must reach the point where we can say that:

  • In a person of genetic type A.
  • Who has too many bad bacteria B.
  • Too few good bacteria C.
  • Caused by a shortage of phages D and E.
  • Who eats a diet deficient in fungi F and G that, collectively, causes a shortage or excess of neurotransmitters H and K.
  • Making mental health problems L inevitable.

What can we do to protect our physical and mental health until we reach that nirvana of knowledge?

One thing is to be aware of the chemicals that may impair, damage or destroy our healthy gut biome. The more natural your diet, the fewer processed foods and drinks you consume, the better, with some exceptions. Foods that are prepared using various fermentation techniques are helpful.

It may also be wise to avoid antibiotic misuse. Why? Antibiotics, by their very nature, kill vast numbers of bacteria. In recent history, people have grown accustomed to asking for antibiotics, in the mostly false belief that they can cure a common cold or flu. They cannot, but they can kill much of the microbiome that enhances our immune system.

Recent research has found that when people eat 50g of fibre a day, are physically active and eat very little meat, their risk of bowel cancer is vastly reduced. Those who only eat 15g daily have a much higher risk of the same cancer. Why? Among other benefits, the fibre is broken down to create molecules which have anti-inflammatory properties.

Taking pre-biotics, pro-biotics and post-biotics are also thought to keep our microbiome healthy, but we are just beginning to learn how they work. We are still not at the point where we can personalise their consumption. We can say, more generally, that eating whole, high-fibre, and fermented foods increases the biodiversity in our gut.

What wholesome, high-fibre, fermented foods will you eat to maximise the chances of helping your microbiome to keep you mentally healthy?

Professor Nigel MacLennan runs the performance coaching practice PsyPerform.


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