SOIL / GUT / BRAIN - Part 1
Electron microscope image of bacteria
1/1000th of a millimeter
Part 1. Are we just meat puppets?
‘Meat puppet’ is a derogatory term for someone who is unable to think for themselves. New research into the gut biome suggests that signalling from the bacteria in our gut might be influencing our behaviour and even personality in surprisingly powerful ways.
The next frontier of human health is emerging as the understanding of the biome that resides in our gut and how this is connected to the world around us and our physical and mental wellbeing.
We tend to think of our guts as being our ‘insides’ but actually our entire digestive system should be thought of as more of our ‘outside’ as it has direct contact with substances and microbes that come from the external world and it acts as a barrier to our true insides, protecting us from potential dangers, filtering only what we need and expelling what we don’t, this system is intricately controlled by a network of 100 million nerve cells that often get referred to as our second brain.
The Vagus Nerve
The vagus nerve, known as the pneumogastric nerve, governs multiple internal organ functions, encompassing:
Digestion
Heart rate regulation
Breathing control
Cardiovascular activity management
Reflex actions like coughing, sneezing, swallowing, and vomiting
The Gut Brain Axis
This two way connection is called the gut-brain axis. This intricate network facilitates the transmission of essential information from the gut to the brain, employing a diverse array of signalling molecules, including neurotransmitters like serotonin and glutamate, as well as gut hormones. These biochemical messengers collectively exert profound influences on various aspects of human physiology, encompassing sleep regulation, mood modulation, pain perception, stress responses, and appetite control.
This understanding of the connection between the gut and the brain through this super information highway explains many phenomena we think should be limited to functions of the head such as nervousness, often felt as ‘butterflies’ in the stomach as when we are stressed signals are sent to the gut from the brain and blood flow is reduced leading to digestive problems, similarly, when our gut is inflamed we will feel it as stress in the mind.
Perhaps we should take these messages more seriously as we use the phrase ‘gut instinct’ or saying ‘trust your gut’.
In 2010, neuroscientist Diego Bohórquez of Duke University in Durham, North Carolina, made a startling discovery while looking through his electron microscope. Enteroendocrine cells, which stud the lining of the gut and produce hormones that spur digestion and suppress hunger, had feet like protrusions that resemble the synapses neurons use to communicate with each other. Bohórquez knew the enteroendocrine cells could send hormonal messages to the central nervous system, but he also wondered whether they could "talk" to the brain using electrical signals, the way that neurons do. If so, they would have to send the signals through the vagus nerve, which travels from the gut to the brain stem.
He and colleagues injected a fluorescent rabies virus, which is transmitted through neuronal synapses, into the colons of mice and waited for the enteroendocrine cells and their partners to light up. Those partners turned out to be to vagal neurons, the researchers report today in Science.
In a petri dish, enteroendocrine cells reached out to vagal neurons and formed synaptic connections with each other. The cells even gushed out glutamate, a neurotransmitter involved in smell and taste, which the vagal neurons picked up on within 100 milliseconds—faster than an eyeblink.
That's much faster than hormones can travel from the gut to the brain through the bloodstream, Bohórquez says. Hormones' sluggishness may be responsible for the failures of many appetite suppressants that target them, he says. The next step is to study whether this gut-brain signalling provides the brain with important information about the nutrients and caloric value of the food we eat, he says.
There are some obvious advantages to superfast gut-brain signalling, such as detecting toxins and poison, but there may be other perks to sensing the contents of our guts in real time, he says. Whatever those are, there's a good chance the benefits are ancient—gut sensory cells date back to one of the first multicellular organisms, a flat creature called Trichoplax adhaerens, which arose roughly 600 million years ago.
So we’ve identified that an incredible 2 way communication system operates on the gut brain axis but if this is like the body’s internal internet, who’s using it?
We are meat puppets!
Who is really in charge?
The human gut is home to trillions of microorganisms, including various species of bacteria. This community of microorganisms is known as the gut microbiota. The composition of this microbiota can vary from person to person, influenced by factors such as diet, genetics, and environmental exposures.
As mentioned above the gut can give feedback to the brain to directly control behaviour but what is now becoming clear is that the ‘bugs’ or more properly the bacterial biome of the gut is creating signalling chemicals for their own means.
It’s been suggested by some researchers of the gut biome that microorganisms have such strong signalling mechanisms that they are manipulating the actions of their hosts, we might all be meat puppets controlled by the bacteria living in our gut!
Gut bacteria metabolise the food we eat and produce various metabolites as byproducts. These metabolites include neurotransmitters, short-chain fatty acids, and other bioactive molecules.
These short chain fatty acids (SCFAs) can have a direct influence on our mental health in a number of ways, firstly they can stimulate the production of serotonin and certain other gut hormones, which in turn exert effects on emotion, learning, and stress responses. SCFAs can directly affect the vagus nerve, which connects the brain and the gut, also, some SCFAs can enter into blood circulation, and then cross the blood-brain barrier to modulate the responses to inflammation and the production of neurotrophic factors that stimulate neural growth and development.
Mental health, mood and personality
There is ongoing investigation into how the gut microbiome could impact mental health, particularly mood disorders like anxiety and depression, often associated with gastrointestinal issues like irritable bowel syndrome (IBS). Notably, the majority of serotonin, a key neurotransmitter in mood regulation, is manufactured by gut bacteria.
Recent studies in mice provide support for this idea, as does the use of vagus nerve stimulation as a therapy for treatment-resistant depression. Moreover, the gut microbiome's involvement in brain diseases such as Parkinson's and Alzheimer's, as well as its potential influence on infants' temperaments, warrants further exploration.
Gut microbes may also wield influence over our dietary preferences, effectively directing our food choices. Research has already demonstrated their ability to affect the eating habits of flies. This phenomenon may be linked to certain types of bacteria encouraging the consumption of specific biomolecules, like sugar, to fulfil their nutritional needs. Consequently, our food cravings may, in part, be driven by the composition of microbes residing in our gut.
The bacteria in our gut each consume certain nutrients and have evolved with us to be able to signal cravings through their chemical manipulation of us, their host’s nervous system so we feed them what they want, not what we want or what is good for us.
Craving sugar? It might not be you but your bad bugs!
Eat a lot of highly processed foods rich in refined sugars and those bacteria proliferate, the more of them that ‘like’ those foods the stronger the signalling they can produce making us crave more. Unfortunately the more junk you eat, the more ‘they’ want and they will make you crave it. The knock on effect of this can have a detrimental effect on our mental health, affecting not just mood but some research suggests personality as well.
Gut bacteria can influence the production and availability of neurotransmitters like serotonin and gamma-aminobutyric acid (GABA). These neurotransmitters can affect mood, anxiety, and behaviour when their levels are altered in the brain.
Imbalances in the gut microbiota, known as dysbiosis, have been linked to various mental health conditions, including anxiety, depression, and even neurological disorders like autism and Parkinson's disease.
Research in this field is ongoing, but it is becoming increasingly clear that the gut-brain axis plays a significant role in influencing behaviour and mental health. Understanding how gut bacteria can influence behaviour through chemical messaging on the vagus nerve is a critical area of study, and it has the potential to lead to new therapies and interventions for mental health and neurological conditions.
Perhaps one of the most mind blowing discoveries recently is that the variety and composition of the gut microbiome can not just be related to but can cause personality traits!
‘The abundances of specific bacterial genera are shown to be significantly predicted by personality traits. Diversity analyses of the gut microbiome reveal that people with larger social networks tend to have a more diverse microbiome, suggesting that social interactions may shape the microbial community of the human gut. In contrast, anxiety and stress are linked to reduced diversity and an altered microbiome composition. Together, these results add a new dimension to our understanding of personality and reveal that the microbiome–gut–brain axis may also be relevant to behavioural variation in the general population as well as to cases of psychiatric disorders.’
(Selected from the abstract)
The paper linked above shows potential links between various gut bacteria and personality traits and mental conditions. We now have an understanding of how actual species of gut bacteria directly affect personality traits that previously could be considered to be innate or simply determined by our own genetics, not the genetics of our passengers.
The table below shows the incredible links between serious mental conditions and species of gut bacteria.
Sociability and gut health.
You might be interested to note that a character trait of sociability is linked to gut health, it appears that this is a two way relationship.
An Oxford University study from 2020 found that sociable people have a higher abundance of certain types of gut bacteria and also more diverse bacteria,
The full paper 'Gut microbiome composition and diversity are related to human personality traits' can be read in the journal Human Microbiome.
Dr. Katerina Johnson, from Oxford University's Department of Experimental Psychology, explores the connection between the gut microbiome and behavioural traits in a recent study. Her research, published in the journal Human Microbiome, reveals a significant relationship between the composition and diversity of the gut microbiome and personality differences, such as sociability and neuroticism.
Her findings suggest a potential link between the gut microbiome and social behaviour. People with more extensive social networks tend to exhibit a more diverse gut microbiome, typically associated with better overall gut and general health. Conversely, individuals experiencing higher stress and anxiety tend to have a less diverse gut microbiome, it’s easy to see how this relationship can cause positive and negative feedback loops, the more social a person is, the more diverse their gut biome is making them more sociable and vice versa.
Not feeling very sociable? You might blame your gut biome.
Social butterflies or life and soul?
Social engagement can help reduce stress, and stress is known to affect the gut microbiome negatively. Chronic stress can lead to imbalances in the gut microbiome, potentially contributing to gastrointestinal problems and other health issues. Therefore, being more sociable may indirectly support gut health by reducing stress. But, if the person is naturally not sociable, forced sociability can cause stress negatively affecting gut and digestive function despite the potential benefits that are possible from exposure to greater microbial diversity.
How can we get back in the driving seat?
Because our relationship with our gut bacteria involves a two way communication we can take direct action to set about a positive feedback loop and improve our cravings, our mood, our overall health and immunity and potentially certain personality traits simply by modifying our diet.
We write more about improving biome diversity in Pt 2 but one of the direct actions we can take is the ‘cold turkey’ approach.
One of the biggest cravings for many people is that of sweet things or simple carbohydrates, this can especially be hard to shift as the critters in our gut really know how to get us into the fridge or out to the shops for chocolate bars. The way to stop them is to simply stop.
If we stop feeding the bacteria that crave sweet things they die and can no longer send these signals with enough persuasion to influence our behaviour.
When dealing with sugar cravings it might be prudent to not go all out and remove all forms of carbohydrate, just the very sweet processed things you’re craving, replacing the Snickers with fruit is a good idea rather than cutting the entire food group.
When we restrict any major macronutrient from our diet, be it carbohydrates, fats, or proteins, it can lead to a significant alteration in our gut microbiome. Remarkably, this transformation can occur in as little as three days. The composition of our gut microbiome is heavily influenced by our dietary choices. Those who primarily consume animal protein have entirely distinct gut microbiomes compared to those who follow plant-based vegan diets.
This phenomenon is one reason why diets often yield short-term results, as they essentially reset an unhealthy gut microbiome that existed before the diet. Paradoxically, it's also why diets often fail in the long run (with a staggering 99% failure rate). The gut microbiome might shift to an extreme that leaves you feeling worse, stuck, or ultimately back where you started.
For instance, if you eliminate carbohydrates or any particular food group, your blood sugar levels might initially appear to improve. However, as the carb-digesting bacteria diminish during the diet, reintroducing carbs may lead to reduced tolerance and erratic blood sugar levels, causing issues like brain fog, shakiness, lightheadedness, and digestive discomfort.
In the world of nutrition, balance reigns supreme. Optimal sources of carbohydrates include prebiotic fibres, a variety of vegetables, and fresh fruits. Researchers advise that for a thriving and diverse gut, one should aim to incorporate 30 different plant varieties into their weekly diet. This could involve consuming items like orange and purple carrots, red and sweet potatoes, green chard, kale, spinach, fresh ginger, rosemary, cilantro, avocado, and more. If you encounter difficulties such as constipation or bloating, consider cooking, sautéing, roasting, or steaming these foods to aid in digestion.
In conclusion
Knowledge is power. The most important takeaway from this is to recognise that the ‘self’ is more complex than we might understand and that some of our behaviour is not strictly ‘our’ behaviour.
Far from absolving personal responsibility for our actions, this knowledge can be very empowering, helping us to rise above these simple cravings that might be detrimental to our mental and physical health and take a third person approach to rebalancing our system and controlling who are the guests in our gut hotel.
Eating a large variety of ideally organic foods that have come from complex ecosystems is of huge importance to creating a better balance within our biome, we outline this in more detail in part 2.