Collectively, we’re getting more in tune with our feelings. Take a look at the world around us and you’ll see that mental health is being taken much more seriously than it has historically. Now it is more on par with physical illnesses or injuries. One of the key components we acknowledge in mental health is stress, but despite the word having decidedly negative connotations, stress itself is actually neither positive nor negative! It’s one of the body’s natural defences against real or perceived danger, and it’s how our brain naturally reacts to extreme change. Stress isn’t purely negative; it’s an automated response that can sometimes be beneficial to health and wellbeing in its role as the body’s ‘warning system’, and has previously been suggested to have a positive impact on short term brain function and cognition. Of course, at other times, stress can be detrimental - but did you know that your gut can play a role in alleviating stress?
What are the types of stress?
When we talk about stress, there are two main types that we refer to. These are acute and chronic, and one of the main differences in how we classify them is in duration. Acute stress tends to be brief and is often the kind we associate with anxiety. It can be brought on by things we are anxious about, such as an exam, work deadline or job interview. Although it can feel very impactful at the time, bringing on symptoms such as headaches, emotional distress and tendon pain, acute stress is not thought to have the same lasting damage as the other classification, chronic1 stress. Chronic psychological stress tends to be much more long-term and is thought to be the result of pressure building up over a long period of time, and so is more closely connected to lifestyle and behavioural triggers. Examples of this could include bereavement, unemployment or financial difficulties.
The hypothalamic-pituitary-adrenal (HPA) axis
An interaction between three glands in the body, releases a stress hormone called cortisol in response to stress. This hormone affects many parts of the human body, including the brain, muscles and body fat. It is believed that permanently increased cortisol due to stress, if left unmanaged, can irreversibly impact physical and mental health2.
What is the connection between gut health and stress?
Have you ever wondered:
- Where that ‘butterflies in the stomach’ feeling comes from?
- Why anxiety is often accompanied by nausea?
- Why we can feel ‘hangry’?
The answer lies with the channels of communication in the body. The brain and gut send signals and information to each other in a mechanism known as the ‘gut-brain axis’3. This goes some way to explaining why mood and the gut can be so closely connected! Science is still uncovering a lot of new information about how the gut interacts with the rest of the body. So far, we know that the relationship between the brain and the gut it is not only about routes of neural communication, but it also involves endocrine (hormone) and immune pathways4.
Can stress affect the gut microbiome?
The nature of the gut-brain axis means that the gut can be sensitive to heightened emotions signalled by the brain. This can be shown in a number of ways, including changes to how the intestine moves contents, gut barrier permeability and enhanced gut sensitivity. Stress can also lead to long-term changes in the composition of the gut microbiome and its metabolic activity. Studies have demonstrated that cortisol and changes to the body’s immune system due to stress have direct negative effects on the gut microbiome. When the gut’s microbial balance isn’t right, known as dysbiosis, it could impact the gut’s ability to fight pathogens and viruses. They could become more easily attached to the gut wall and may cause problems such as sudden diarrhoea.
Can the gut microbiome affect stress?
The bidirectional nature of the gut-brain axis means that signals can be sent both ways; stress can impact the gut microbiome, but the gut also sends signals to the brain on its condition and activity. The vagus nerve5 sends information from the gut to brain regions involved in stress response and feeds information from the brain back to the gut. Significantly, almost 90% of the neural communication between the gut and the brain starts in the gut, which indicates that the gut could have a powerful influence on brain function, including manipulating the feeling of stress. So, if you’re feeling rising stress levels, it may be a good idea to take a look at the health of your gut, which may have played a part!
The composition of gut bacteria can profoundly influence brain and behaviour in additional ways too. The gut microbiome helps the host produce neurotransmitters, chemical compounds that affect how the brain functions. Serotonin is a well-known example, produced by the body’s nerve cells. It’s an important contributor to happiness and wellbeing, but approximately 90% of serotonin actually originates in the gut!
What does it mean for the future of stress management?
Although we are just beginning to understand more about the significant role of the gut-brain axis and its wider influence on overall wellness, there is clear evidence of the influence of stress on gut microbiome, and equally the gut microbiome influence on stress modulation. The condition of the gut and how we’re feeding our gut microbiome can influence how we cope with stress levels. In the future, there is a possibility of managing or alleviating stress and anxiety with changes to the diet.
- Vedhara, K. et al. Acute stress, memory, attention and cortisol. Department of Experimental Psychology, University of Bristol (2000)
- Neurobiological and Systemic Effects of Chronic Stress
- The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems
- The Brain-Gut-Microbiome Axis
- Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders
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