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Anxiety, Depression and Gut Health

Updated: May 12, 2023

It’s National Mental Health Awareness Week this week, so it seemed appropriate that this blog will discuss the link between anxiety, depression and gut health.

Studies show that as many as half of those diagnosed with IBS, also suffer from psychological disorders including anxiety and depression. From my experience working with IBS sufferers, I believe the correlation is much greater than what these studies show. One of the questions I ask all of my clients is if they have ever been diagnosed with mental health conditions, and nearly every single person says yes. However, there is a lot of misunderstanding around how this impacts gut health. Many of those diagnosed with IBS have been led to believe that the condition is caused by their mental health, but more recent research is showing that the ‘gut-brain axis’ is actually a two way street, where the imbalances in your gut directly affects what’s happening in your brain, and vice versa.

What is the ‘gut-brain axis’?

The ‘gut-brain axis’ is the bidirectional link between the autonomic nervous system (ANS) and the enteric nervous system (ENS) of the body. Both the ANS and ENS can impact mental health and IBS in different ways.

Enteric Nervous system (ENS)

The digestive system has its own nervous system called the enteric nervous system (ENS), which is two thin layers of more than 100 million nerve cells lining your gastrointestinal tract from esophagus to rectum. It is sometimes referred to as the second brain but unlike the brain, Its main role is controlling digestion, from swallowing to the release of enzymes that break down food to the control of blood flow that helps with nutrient absorption to elimination.

The ENS may trigger big emotional shifts experienced by people coping with IBS. For decades, researchers and doctors thought that anxiety and depression contributed to these problems. But studies show that it may also work the other way around. Researchers are finding evidence that irritation (caused by poor diet, eating habits, dysbiosis and bacterial overgrowths) in the gastrointestinal system may send signals to the central nervous system (CNS) that trigger mood changes. There have even more recently been specific strains of bacteria found in our guts that have been found in higher levels in those with clinical depression. These new findings may explain why a higher-than-normal percentage of people with IBS and functional bowel problems develop depression and anxiety.

The Autonomic Nervous System (ANS)

The autonomic nervous system has two branches -

the sympathetic nervous system: involved in the ‘fight or flight’ response. This branch of the nervous system is really an evolutionary advantage, which ensures that we can summon up the energy during times of great stress to run away from whatever threat in order to survive. And it's meant to last only for short bursts or short duration that releases stress hormones that divert the blood flow away from the organs and more towards the big muscles so that we could run away. During this time the usual automatic processes like digestion get put on standby because your body is saying this is no time to digest food, this is the time to survive and run away. The problem is, most people live pretty busy, stressful lives these days, and our nervous system isn’t great at distinguishing between being chased by a tiger and having an inbox full of emails that desperately need to be answered, but your family is also expecting dinner to be on the table soon. Both of these situations are stressful and so our body responds the same, by focusing your body’s resources on removing the “threat”, and putting automated processes like digestion on the backburner. This is exactly how mental health conditions like anxiety can drive IBS symptoms, as most people who suffer with anxiety are constantly stuck in a state of ‘fight or flight’.

Parasympathetic nervous system - This is essentially the opposite of the sympathetic nervous system, and often referred to as ‘rest and digest’. It controls bodily functions when a person is at rest. Some of its activities include stimulating digestion, activating metabolism, and helping the body relax. This is the state you want to be in when eating to promote better digestion, yet many IBS sufferers (especially those with anxiety) are stuck in ‘fight or flight’.

As you can see, the gut-brain connection is a two way street, where the gut can impact mood and emotions, and the brain can impact digestion.

What you can do about it

The key to overcoming gut-brain axis issues is to work on both the physical gut imbalances related to the ENS, that have the potential to impact mood, as well as work on your nervous system “state” to help promote better digestion. Basically, work on both directions of the gut-brain axis.

Direction 1 (gut-to-brain) -

Improving this part of the gut brain axis involves addressing the gut microbiome (all the microbes that live in our guts), and removing pathogens. When the gut microbiome is dysbiotic (out of balance), this can have an impact on your mood. Studies have demonstrated that the gut microbiome influences stress reactivity and anxiety-like behaviour. Recent research examined the composition of gut bacteria in patients with depression compared to healthy individuals and reported significant differences with increased population of Bacteroidetes, Proteobacteria, and Actinobacteria, and decreased population of Firmicutes in patients with depression. Additionally, microbes produce metabolites such as butyrate, SCFA, GABA and tryptophan which travel to the brain via blood vessels and regulate neurological function.

Gut pathogens and bacterial/fungal overgrowths are common in those with digestive issues. It is now accepted that gut pathogens can cause anxiety, depression and cognitive dysfunction. Campylobacter jejuni, a pretty common gut bacteria in those with IBS symptoms, given to rats in small doses led to anxiety-like behavior without a detectable immune response. So even if you don’t have IBS symptoms, your anxiety could still be caused by a low-grade gut infection like Campylobacter.

The mechanism is thought to involve cytokines, the vagus nerve and bacterial molecules, highlighting that very often no one mechanism is working alone within the gut-brain axis.

Identifying pathogens in the gut is best done through a comprehensive stool test, and treated with medication or antimicrobial herbs.

Improving the balance of the gut microbiome (i.e. increasing beneficial microbes) is best done through a diet containing a wide variety of plant foods (fruits, vegetables, nuts, seeds and wholegrains), which are your microbes main food source. A recent study showed that those who eat 30+ different types of plant based foods each week compared to those who ate 10 or under showed a significant difference in microbiome diversity, so the key here is making sure you get lots of variety when it comes to plant foods.

Additionally, probiotic and prebiotic supplements can help to improve microbiome diversity and function.

Direction 2 (brain-to-gut) -

While improving the gut-to-brain connection is focused on your gut microbiome, improving the brain-to-gut connection is centered around the state of your nervous system (fight or flight vs rest and digest), how your mood impacts your digestion, and your eating habits.

As previously discussed, your nervous system state can directly impact your body’s ability to digest food. If you’re often in a state of ‘fight or flight’, your body will not think it’s “safe” to digest, which can result in symptoms like bloating, gas, diarrhea and constipation. This can cause anxiety itself, as most people believe it is the food they are eating causing the problem, and therefore develop anxiety around eating in fear of developing symptoms. This can also lead to depression, due to heavy food restrictions and debilitating symptoms which can make you feel like you’re missing out on life.

Additionally, the way you eat can impact your nervous system state and ability to digest food. If you’re constantly on the go, rushing while eating or eating while distracted, your body can perceive this as stress.

An often-cited 1987 study, published in the journal Gastroenterology, illustrates how metabolism and digestion are altered under perceived distraction and stimuli. In this study:

  • Participants consumed a mineral drink while they were in a relaxed state. Researchers found that participants absorbed 100 percent of the drink's nutrients in this relaxed state.

  • Then the participants were asked to concentrate as two different people spoke to them simultaneously. In one ear, someone spoke about intergalactic space travel, while in the other ear, someone spoke about financial planning. When the subjects were exposed to this listening conflict and given the same mineral mix, they showed a significant reduction in assimilation that lasted up to an hour afterward.

The simple act of attending to two stimuli at once dramatically altered their metabolism, even though we might not normally consider this to be very stressful. Consider that people often read the newspaper, watch TV, or drive a car while eating. These distracting stimuli can to some degree impair the ability to digest fully.

Diaphragmatic breathing is one of my favourite techniques to help downregulate the nervous system and move towards a state of ‘rest and digest’. Diaphragmatic breathing or belly breathing is a breathing pattern that involves actively trying to breathe into the diaphragm.

The diaphragm is located at the base of the chest and it contracts and flattens when you inhale. When someone is stressed/anxious, it is a natural reaction to begin breathing shallowly and into the upper chest. This breathing pattern is associated with 'fight or flight', where breathing into the diaphragm does the opposite by activating 'rest and digest'. Training yourself to breathe into the diaphragm when stressed or anxious can help to mitigate digestive symptoms that may occur as a result of your body being in a state of 'fight or flight'. Taking 3-4 big belly breaths before you eat, can help to let your body know that it is time to digest, resulting in optimal production of digestive juices needed to break down foods.

In short - focusing on moving towards ‘rest and digest’ through diaphragmatic breathing, slowing down when you eat, and removing distractions can promote better digestion, which means less fear and anxiety around food and less restrictions.

In summary:

Anxiety, depression and other psychological and mood disorders are complex conditions with a variety of root causes that differ from client to client. Not everyone who suffers from anxiety or depression is going to have their symptoms improve completely through healing the gut.

But, for those with IBS-type symptoms, it can be a relief to know that this might be the case for you, and that it isn’t just “all in your head”.

If you’re struggling with IBS with anxiety or depression, I’d love to help you! Start by booking a free 20 minute introductory call here.

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