Hidden in the walls of our digestive system is something extraordinary. Scientists have known about it for a while, but new technology is taking the research to the cutting edge. What is being discovered there will revolutionise the way we think about mental and physical health.
What happens in our head has a lot to do with what’s happening further south, in what scientists affectionately call ‘the brain in our gut’. It has a strong connection to the brain in our head and together, they are key players in mood, and mental health.
The brain in our gut, or the second brain as it is also called, is made up of more 200-600 million neurons, arranged in the intricately folded tissue that lines the gastrointestinal tract. With firepower like that, it’s not surprising that the gut does so much more than deal with food and the messier parts of being human.
It plays a critical role in mental and emotional functioning by sending information to the brain and directly influencing things like feelings of stress, anxiety and sadness, as well as memory, decision-making and learning. The brain in our gut is not capable of thought as we know it, but it communicates back and forth with our main brain, playing a critical role in our mental and emotional well-being.
Unhappy mind. Unhappy belly. Which comes first?
It’s no secret that anxiety, stress and depression often bring unhappy bellies with them, by way of irritable bowel syndrome, constipation, diarrhea, bloating and pain. For decades, doctors thought that stress, anxiety and depression were the cause, but now it seems that it’s actually the other way around. Irritation in the gastrointestinal system seems to send signals to the brain that trigger mood changes. We know that probiotics seem to alleviate the symptoms of anxiety and depression and this might be why.
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The gut is not only important for physical health, it’s also critical for mental health. What’s fascinating is the direction of influence. The longest nerve exiting the brain is called the vagus (actually they are one pair of 12 pairs of nerves that run from the brain). It runs from the brainstem to the belly and touches the heart and most major organs along the way. Here’s the fascinating part. About 90% of the fibres in the vagus, carry information from the internal organs in the chest (such as the heart) and the abdomen to the brain, not the other way around.
Our language holds evidence of this – we were talking about it well before we knew it. If you’ve ever been directed by ‘gut instinct’, ‘gone with your gut’ to make a decision, or ‘listened to your heart’, you’re likely getting signals from this second brain in your belly.
Messages also travel the other way, from the brain to the heart and the gut, also via the vagus nerve but without a doubt, the main direction of information flow is from the gut to the brain.
The Role of Gut Bacteria.
As well as neurons, there is another major player in the gut-brain connection – the 100 trillion bacteria that set up home inside your gut. According to professor of physiology, psychiatry and behavioral sciences at UCLA, Emeran Mayer, gut bacteria contains phenomenal wisdom that gets sent to the brain. They affect our behaviour every minute of every day from the day we are born, and possibly before.
A Fascinating Study: From Extroversion to Introversion via the Gut
Mayer’s research has shown how the specific combinations of bacteria in the gut might influence the wiring of the brain, and in turn affect such things as temperament, mood and learning. Other researchers have also explored a possible connection between gut bacteria and behaviour, and they’ve made some remarkable discoveries.
In one study, when the gut bacteria of timid mice was transferred into the gut of extroverted mice those extroverted mice became more anxious. It also worked the other way. When the timid mice received the gut bacteria of the bold mice, the timid mice because more bold and extroverted. Aggressive mice calmed down when scientists adjusted the their gut bacteria by giving them probiotics or antibiotics.
Another Study: The Connection Between Gut Bacteria and Temperament
Research has found correlations between temperament and the presence of specific intestinal bacteria in toddlers, particularly boys. The connection was independent of history of breastfeeding, diet and the method of childbirth. Here’s what they found:
- The children with the most genetically diverse types of gut bacteria were more positive, curious, sociable and impulsive.
- In boys, extroversion was associated with an abundance of particular types of bacteria (Rikenellaceae and Ruminococcaceae families and Dialister and Parabacteroides genera).
- In girls, self-restraint, cuddliness and focussed attention were associated with a lower diversity of gut bacteria.
- Girls with an abundance of a particular family of bacteria (Rikenellaceae) seemed to be more fearful than girls who had a more balanced diversity of microbes.
This research is still in its early days, so we still don’t know what a healthy tummy would look like in terms of the combination of gut bacteria, or what factors would influence this. It is possible that the perfect balance of microbiome will vary for all of us. For this reason, the researchers caution against trying to change a child’s gut microbiome just yet.
The Gut and Depression.
Depression is widely attributed to a drop in serotonin, a neurotransmitter that is responsible for mood. What’s extraordinary is that only 5% of the body’s serotonin is stored in the brain. The other 95% of the body’s serotonin is stored in the gut.
It’s not surprising then, that the most commonly used antidepressants that work on changing serotonin levels often come with a side of gastrointestinal issues. It’s also not surprising that the gut might play more of a role in depression than we yet realise. Research continues to look down this track for answers.
The Gut and Anxiety.
Researchers have found that young adults who eat more fermented foods (which contain probiotics) have fewer symptoms of social anxiety. As explained by Psychology Professor Matthew Milimire, ‘It is likely that the probiotics in the fermented foods are favourably changing the environment in the gut, and changes in the gut in turn influence social anxiety … the microorganisms in your gut can influence your mind.’
Food and the Comfort Factor.
The need for comfort rarely sees us diving for the celery. Pity. Instead, ‘comfort food’ tends to be high fat, high energy food.
The relationship between food and mood isn’t all in our heads. Yes comfort food tastes delicious, smells delicious and might remind us of times we felt happy and secure, but there’s so much more to it than that, as a team of Belgian researchers have shown.
The researchers delivered nutrients to the stomachs of participants via a nasogastric tube, with the intention of taking away the smells, tastes and memories that are typically associated with comfort food. The participants were given either ordinary saline solution or an infusion of fatty acids. Without knowing what they were receiving through the tube, those who received the fatty acids reported half the levels of sadness and hunger compared to those who received the saline. This also showed up in brain scans. Very quickly after fatty acids hit the stomach, scans showed greater activity in the part of the brain that moderates emotions.
Stress and Food
Early research found that stressed-out mice would opt for a higher-fat food (peanut butter) over regular chow. Not surprisingly, they put on more weight than their less stressed friends. In times of stress, the gut amps up the production of ghrelin, a hormone that signals hunger to the brain. Research in humans has found similar results. In a recent study, couples were found to have significantly higher amounts of the appetite-triggering hormone following an argument. The researchers stop short of suggesting that unhealthy relationships cause poor food choices, but they acknowledge that the correlation is a strong one.
There seems to be little doubt that one of the ways stress influences behaviour is via the gut, specifically on the production of ghrelin, which sends messages to the brain around appetite and food choices.
Could gut bacteria be behind this?
Mayer points out that the last 50 years has seen a dramatic rise in autism, multiple sclerosis, Parkinsons and obesity. All of these have altered gut bacteria and brain-gut interactions. At the same time, throughout the last fifty years, we have dramatically changed the way our food is produced and processed, and the way we use antibiotics. Has the way we’re doing things lead to the dramatic increases? At this stage, it’s only speculation, but it’s an area of research that is gaining traction.
Where to now?
Mental health is not all in our head. Neither is mental illness. Finally, science is giving us real proof of this. There is little doubt that mental and emotional health is influenced by the state of our gut. The research is exciting and is promising to revolutionise treatments for a range of conditions and the way we take care of our mental health.
The research is constantly evolving, but what we know for sure is the importance of being attentive to the state of the gut and doing what we can to keep it healthy. It holds our second brain, and quite possibly, one of the vital keys to our mental and emotional well-being.
Oh…. my son has so many problems with ADD and drug usage…THIS would help explain and stop his depression , drug use and self harm. Thank you.
For years I had many problems associated with my bowels. Usually it was constipation and lack of motility. I saw many gastroenterologists who offered very little advice. As a child I had been on antibiotics constantly, my tonsils were removed at 5 1/2 but still I would vomit, nothing helped. It took until I was in my mid 50’s to find a specialist who did breath testing for lactose and fructose malabsorptions. I tested positive to fructose malabsorption and have been much healthier and happier for the past few years. Knowing why I had suffered for most of my life from anxiety had a huge positive affect on my mental health and outlook. Changing my diet and including the right type of fermented yoghurt has improved my quality of life enormously. My bowels still are a challenge at times but my outlook on life is so much more positive and my emotions are more controlled.
Thanks so much for sharing this Suzanne.
Interesting, succinct and informative. This opens up a whole new way for me to look after myself.
Thanks for writing this article in a way that makes it easy to read and understand.
Thanks Dave. I’m so pleased the information is helpful.
What foods do you recommend?
Generally speaking, fermented foods and foods that contain probiotics and prebiotics are good for gut health and mental health. Here is an article with some examples https://www.heysigmund.com/a-simple-way-to-reduce-social-anxiety/. If you start including fermented foods in your diet, it’s important to do it slowly. The article on the link explains why. A naturopath would be able to help you with a diet that is tailored more for you and which is more targeted for your symptoms.
I have been having a bad digestive health for years and now as I am changing my diet and adding probiotics I feel my mood shift. Anxiety and depression are surfacing as the bad bacteria is being released… enema can help cleanse the colonic bad bacteria. I always feel better after enema.
I’ve also felt gut problem ,but I couldn’t relate all this with stress……Even I didn’t know earlier that this is happening because of stress…..I’m taking antibiotic for two years….But I can feel that belly pain or gastronomy problem is happening after stress.Your article helped me more clearly to understand about second brain….Keep sharing more articles like these…..thank you.
Thanks for this. It’s a great article. So what is the best diet or supplements to take?
It can be different for everyone, but if you speak to a naturopath or pharmarcist they should be able to steer you in the right direction.
Hi, I first had loose watery stools and stomach gas for about 10 days and then got into depression. This shows that the gut plays a major part in mental illness from my experience. There can be other reasons but for me it is my stomach.
This. This relates so much with the Serotonin Power Diet that I have been on for the last three weeks and have seen significant changes to my health (for the better) than previously. I am so glad to see more and more concrete evidence of how it is that mental illnesses are just a result of chemical imbalances and what that all means.
What’s a serotonin power diet
Best to look it up. High carb low fat diet. It worked well for me to get me out of the funk I was in at the time. That was four months ago. It is worth it to get out of the cycle of fatigue that you may find yourself in when life happens, but long term once your body starts feeling good again, you’ll need to start reducing it back to normal levels again.
How would having a Gastric band effect the emotions/ depression/ anxiety based on your findings??? Please
It’s a very good question. I’m not familiar enough with the research around gastric banding to answer it though. A doctor or your specialist would be the best person to talk to about this.
Thanks for this article.
My sister practices an ancient healing art called “VARMAM” … which is being practiced in India by a few. She was telling me that her patients with depression, anxiety, stress and mood swing symptoms … all of them invariably had a very bad stomach condition.
She just administered the touch healing points for the stomach … and they become perfectly alright on the 3rd day. All happy and smiling!
Certainly probiotics is a wonderful food. In India, we take buttermilk regularly in our meals, which helps in overall wellbeing.
God Bless your good work. Your articles are very very nice! My wife keeps reading all of them regularly.
Thank you so much, and for sharing parts of your story. There are so many methods of healing that we need to learn more about. I love hearing when these are being practiced successfully.
I am so happy to read this. Posted immediately. For so long I’ve been (almost yelling) “It’s not mental – it’s physical!!!” unfortunately to those very hard of hearing. ie, the experts.
Validation is so so so sweet! Thank you
You’re so welcome Judith. They are absolutely physical and the research is proving it over and over. I just wish there wasn’t such a lag between the research and mainstream. There are too many things that are being treated with old knowledge, without accounting for the new things that science is discovering. All the best to you.