As you may already know, our brain and gut are connected and constantly in communication with each other. That’s why when we are under stress, our gastrointestinal system also gets affected, impacting how our body breaks down and absorbs food.
The American Psychological Association describes stress as something that can cause changes in our gut microbiome. Stress also affects how easily we feel gastrointestinal processes (visceral hypersensitivity). It can trigger bloating, lead to constipation and or/diarrhoea, and can even impair how we absorb nutrients from our food.
In this article, I tackle a common question many of my SIBO Coaching Clients ask: “Is my SIBO caused by stress?”. But before we dive into how stress can affect our gut, let's discuss first how our digestive tract is supposed to function.
Correct function of the digestive tract
Our digestive tract is one continuous tube from mouth to anus, and is the pathway for all foods and liquids we consume. It is where food is broken down into nutrients which our body uses for energy and survival.
It starts with the mouth, then the oesophagus, stomach, small intestine, large intestine, rectum and then anus. Each section plays an important role in digestion. This means that to digest our food and absorb our nutrients effectively, every part of our digestive tract needs to be functioning correctly and be primed for work.
Our digestive tract works optimally when our nervous system is in parasympathetic mode, otherwise called ‘rest and digest.’
We are in this state when we are calm, happy, relaxed and taking the time to enjoy our meal. In parasympathetic mode, our gastrointestinal secretions and motility increase.
Think of a time you have enjoyed a meal, such as when you’ve been eating with friends and family. If you were feeling calm, you would have been in your parasympathetic ‘rest and digest’ mode. Many of my clients share that they feel a reduction in their symptoms when on vacation. They can often eat foods they wouldn’t be able to at home. This is often due to them being relaxed. This shows how powerful the parasympathetic nervous system is.
Once we have eaten and moved into a fasting state (e.g. between meals or overnight when we’re sleeping), our migrating motor complex (MMC) is activated. This is the sweeper wave that moves food, matter, and bacteria down the small intestine and into the large intestine.
Now that we have a basic understanding of how our digestive tract is supposed to work, let’s take a closer look at how stress affects our digestion.
How stress affects the digestive system
In contrast to the parasympathetic mode, our nervous system switches into sympathetic mode (otherwise known as ‘fight or flight’) when we are under stress. You can compare it to a gas pedal that is triggered to provide our body with the energy it needs to respond to a perceived danger.
The ability to switch to a sympathetic mode is crucial for our survival. If you think about early humans, they needed their bodies ready to fight or flee whenever there was an immediate threat to their lives (a stressor).
Digestion, however, is not a necessary function in the immediate moment when we are in ‘fight or flight’ and is therefore impaired.
How does this happen? This can be explained by looking at how our HPA Axis works.
The HPA Axis
The HPA Axis (hypothalamic-pituitary-adrenal axis) acts as the stress response system of our body. It involves the interaction between our hypothalamus, pituitary gland and adrenal glands.
When we are under stress, our sympathetic nervous system steps in resulting in the stimulation of the HPA Axis. Once this happens, cortisol (our body’s main stress hormone) is released, causing changes to our digestive process. According to an article from Mayo Clinic, cortisol does not only alter our immune system responses, but it can also suppress our digestive system.
Stress and the gut bacteria
A review article published by the National Center for Biotechnology Information also suggests that stress can reshape the gut bacteria’s composition, promoting gut bacterial imbalances and low gut microbiota diversity. It can also trigger pathogenic bacteria that may lead to a leaky gut.
For instance, in a study conducted with university students, Knowles et al. found that certain health-promoting bacteria such as lactic acid bacteria were lower in students who were under high-stress conditions throughout the semester.
Similarly, my 1:1 SIBO Coaching Clients and those who have joined in my Live Well With SIBO: 5 Week Challenge Program often describe how their SIBO symptoms worsen when their stress levels increase or when they have had a stressful day. And the most common SIBO symptom that worsens is bloating.
Stress and SIBO
In this day and age we still have a lot of constant stressors, and our bodies still treat stress (even if it’s not a matter of life-or-death) in the same manner as early humans do. Whether it’s work-related or personal issues, we still experience the same fight or flight state which repeatedly activates our stress response system.
Every time we are under stress, our digestion slows down, impairing our body’s ability to process the food we have eaten and absorb nutrients.
If we’re not processing our food correctly, we can leave food particles available for resident SIBO. This, in turn, can cause more symptoms the more food the bacteria consume. The more gas they produce, the greater the symptoms we can feel.
In addition, stress reduces gastric acid production. Gastric acid is one of our body’s protective agents that help kill the bacteria we ingest from consuming food or water. Insufficiency of gastric acid allows a larger quantity of ingested bacteria to enter our small intestine and cause their overgrowth.
Our immune system is also weakened by long-term or chronic stress. If our immune system doesn’t work correctly, it’s unable to kill or effectively move out bacteria from our small intestine.
A weak immune system also means we are more prone to infection which may require us to use pharmaceuticals like antibiotics. Too much use of antibiotics can affect the balance and composition of the gut microbiome which may increase the risk of SIBO.
Although we can’t avoid stress in our lives, there are ways to manage it to help our body become more resilient. In my next article, I will share with you the importance of having the right mindset and some stress management techniques. Stay tuned!
If you want to learn more about SIBO, check out my Live Well With SIBO: 5 Week Challenge (On-Demand) program. This course gives you instant access to 5 weeks of invaluable SIBO content and expert insights all in one place. Click here to learn more.