Worried sick? How stress & anxiety weaken your immunity—and how to fight back!

When anxiety hits, does your stomach start acting up, too? You’re not alone – we’ve all been there.

Worry doesn’t just live in your mind; its impact can be felt throughout your entire body. When your thoughts are racing or you feel on edge, your gut feels it too. Over time, this can weaken your body’s natural defences and impact your immune system.

Let me explain…

The gut-brain-immune triangle

The gut, brain and immune system form a communication network, involving intricate interactions between the gut microbiota, immune responses and the central nervous system.¹ Your gut microbiome plays a leading role in this dialogue, sending signals through metabolites, nerve pathways and immune mediators.²

Due to this bidirectional communication, stress and depression can influence the consumption of highly palatable foods, which may not be healthy. These foods influence which gut bacteria thrive. Gut bacteria release metabolites, toxins and neurohormones that can alter your eating behaviour and mood. Some bacterial species may encourage dysregulated eating, upregulate stress responsiveness, and potentially increase the risk of depression.³

Your gut lining is crucial; when it’s strong, only the right molecules and nutrients cross over. Under stress, its tight junctions can loosen, allowing more substances, such as microbes and toxins, to leak into the body. This can trigger systemic immune responses and lead to intestinal permeability, which has been linked to autoimmune conditions and gastrointestinal disorders.⁴ Elevated levels of stress hormones such as cortisol can suppress vital immune cells, leading to a weakened immune response.⁵

What happens in the gut when you worry?

When worry lingers, your body remains in a mild but constant state of fight or flight. This survival response floods the body with hormones like cortisol and adrenaline. This is handy if you need to run from danger, but not so helpful if you’re dealing with less urgent stressors.

Inside the gut, the stress response has physical effects; blood flow is redirected away from digestion to the muscles and brain, slowing down the breakdown and absorption of food. The muscles of the gut wall may contract irregularly, leading to symptoms such as bloating, discomfort, constipation and diarrhoea.

Research shows that chronic psychological stress reduces beneficial bacteria such as Lactobacillus and Bifidobacterium, whilst promoting the growth of potentially harmful strains that produce toxins and inflammatory compounds.⁶

These microbial changes can contribute to dysbiosis, a disruption to the balance of your gut bacteria. Over time, dysbiosis can weaken the intestinal barrier, commonly referred to as leaky gut.⁷ When the barrier becomes more permeable, small food particles and bacteria can cross into the blood stream, activating the immune system and keeping it on high alert. This low grade inflammation can make you more vulnerable to illness, fatigue and mood disturbances.⁸

The stress-gut cycle

It’s a two-way street – stress affects your gut, and your gut can affect how you respond to stress. When stress alters your microbiome and weakens your gut barrier, inflammation can increase, and essential chemical messengers, such as serotonin and short-chain fatty acids, become disrupted. These play a vital role in mood regulation.

An imbalanced gut makes you less resilient to future stress. This can lead to ongoing inflammation, lowered immunity and a nervous system that feels constantly overstimulated.⁹

To break this cycle, you need to soothe your mind and nourish your gut, allowing both to regain balance.

How does this affect your immunity?

When your gut is balanced, it acts as both a barrier and a communication hub for your immune system. Approximately 70% of your immune cells are located in the gut, constantly assessing what enters and deciding what to fight and what to tolerate. When stress disrupts the environment, your immune system can become confused or overreactive. Chronic worry doesn’t just wear down your mind; it can quietly tire your immune system, too.

Under chronic stress, changes in the gut microbiome and intestinal permeability can trigger the release of inflammatory molecules, prompting your immune system to enter a state of low-grade inflammation,¹⁰ weakening its ability to respond to real infections and leaving you more vulnerable to colds, slower healing, and even flare-ups of inflammatory conditions.

The vagus nerve, which connects the gut and brain, plays a crucial role in regulating the immune response. Stress suppresses vagal tone, meaning the ‘rest and digest’ signals are dialled down, while fight-or-flight hormones like cortisol and adrenaline are dialled up. Gradually, this can reduce your body’s tolerance to stress and make it harder to return to balance, creating a vicious cycle.¹¹

Supporting your gut during stressful times isn’t just about good digestion but an act of self-care that supports your immunity and overall wellbeing.

Practical ways to support your gut and mood

Take a probiotic and prebiotic – combined, they form a powerful synbiotic that promotes the growth and activity of beneficial bacteria, leading to improvements in digestive health, immune function, and overall wellbeing. See what the research says here!

Eat a diverse fibre-rich diet – a colourful variety of plant foods supports a diverse microbiome and boosts the production of short-chain fatty acids that help strengthen the gut lining and regulate inflammation.¹²

Manage stress with engaging practices like breathwork, vagal toning exercises, meditation and yoga. These techniques help shift your nervous system from a state of fight or flight into one of rest and digest.

Prioritise consistent sleep and manage your circadian rhythm – disrupted sleep or circadian misalignment can impair microbiome resilience and increase inflammation.¹³

Gentle movement and time in nature – physical activity helps to preserve microbial health, reduce inflammation, boost the immune system and improve sleep.¹⁴

Limit gut disruptors – Try to avoid unnecessary antibiotic use, ultra-processed foods, high-sugar foods or high-saturated-fat diets, which reduce microbial diversity and resilience.

Supporting your gut and soothing your nervous system can shield your immune system from stress and constant worry. Sometimes, all it takes is a little rest and regulation!

To learn more about the gut-brain connection check out these two articles –

Any questions? Contact one of our Nutritional Therapists via live chat, weekdays from 8 am to 8 pm.

Worried sick? How stress & anxiety weaken your immunity—and how to fight back!

The gut-brain-immune triangle

What happens in the gut when you worry?

The stress-gut cycle

How does this affect your immunity?

Practical ways to support your gut and mood

References

Questions? Talk to a Nutritional Therapist on live chat!

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