There is a genuine, increasingly well-mapped biological relationship between the gut and the nervous system, and it plays a role in how pain is generated and experienced. This explains the mechanism behind the gut-pain connection - what's actually happening, what the evidence does and doesn't support, and where dietary change realistically fits into a broader pain plan.
What exactly is the gut microbiome?
Your digestive tract is home to trillions of microorganisms. Bacteria, viruses, fungi, and other microbes in your intestines are collectively known as the gut microbiome. Previously thought to be involved with digestive processes only, science now helps us understand that these microbes are active participants in your physiology. They:
● Help digest fibre and plant compounds that human enzymes alone cannot break down
● Train and regulate the immune system, teaching it to distinguish harmless substances from genuine threats
● Produce chemical signals that influence other body processes well beyond the gut itself.
While we know that there are “good” bacteria and “bad” bacteria, research is increasingly pointing to the importance of diversity - a wide, resilient community of different microbial species tends to function better as an ecosystem than any single “good” strain working alone.
How does the gut talk to the brain?
The relationship between the gut and the central nervous system is often called the gut-brain axis, and it operates through several parallel channels:
● The vagus nerve: a direct physical connection running between the gut and the brainstem, constantly relaying information in both directions
● Immune messengers: chemical signals released by immune cells in the gut lining that can influence inflammation elsewhere in the body, including the nervous system
● Microbial by-products, particularly short-chain fatty acids (SCFAs): compounds like butyrate, propionate, and acetate, produced when gut bacteria ferment dietary fibre. SCFAs nourish the cells lining the colon, help regulate inflammation, and can influence signalling well beyond the digestive tract
Crucially, this is not a one-way street. It's tempting to imagine the gut simply “sending signals up” to the brain, but stress, mood, and the state of the nervous system also shape gut motility, gut permeability, and even the composition of the microbiome itself. It is a two-way conversation, which is part of why gut symptoms and pain symptoms so often rise and fall together.
Where does pain fit into this conversation?
Immune signalling originating in the gut doesn't create pain out of nothing. What it can do is influence how sensitive the nervous system is to signals it's already receiving, effectively adjusting the “volume” on pain, rather than switching it on from silence.
This happens through low-grade inflammatory signalling that can sensitise nerve pathways over time, a process closely related to the broader relationship between pain and the immune system. When immune activity in the gut contributes to this kind of neuroinflammation, existing pain, whether it's joint pain, muscle pain, or widespread pain, can feel more intense, more persistent, or more easily triggered.
Why are gut symptoms so common in chronic pain conditions?
If you live with fibromyalgia, endometriosis, or another chronic pain condition and also deal with bloating, altered bowel habits, or general digestive discomfort, you are far from alone. Research suggests a substantial proportion of people with fibromyalgia also meet the diagnostic criteria for irritable bowel syndrome (IBS), and similar overlap is seen with endometriosis and hypermobility conditions. A few things help explain why:
● Shared nerve sensitisation. The nerves supplying the gut and those supplying other painful areas of the body can become sensitised through similar central mechanisms, which is part of why so many people with fibromyalgia also experience visceral (gut-related) discomfort.
● Medication effects. Many pain medications, particularly opioids, slow gut motility and commonly cause constipation and bloating as a side effect.
● Stress and reduced activity. Living with chronic pain is, understandably, stressful, and pain itself often reduces how much people move. Both stress and inactivity independently affect digestion and gut transit.
So the overlap isn't a coincidence or a separate, unrelated problem running alongside your pain, but rather a reflection of shared biology.
Can an imbalanced microbiome make pain worse?
This is where the science gets more interesting, and admittedly, a little less settled. Several strands of research point in a consistent direction:
● Reduced microbial diversity has been observed in people with several chronic pain conditions, compared with pain-free populations
● A less diverse, less resilient microbiome is associated with weaker gut barrier function, sometimes described informally as a “leaky gut”, which may allow more microbial by-products to interact with the immune system
● This can contribute to low-grade inflammation: not an infection or an acute flare, but a persistent, low-level background hum of immune activity that can leave you feeling more fatigued, foggier, and more pain-sensitive, even without anything dramatic happening
It's important to note that most of this evidence is observational, meaning researchers have found associations between microbiome changes and pain conditions, but haven't fully established which comes first. Does an imbalanced microbiome drive pain, does chronic pain (and the stress, medication, and inactivity that often come with it) reshape the microbiome, or is it some combination of both, feeding into each other over time? The research is still evolving, and cause-and-effect is not yet fully settled.
What about food sensitivities and flares?
Many people living with chronic pain notice that specific foods seem to trigger flares. This can lead to the very normal response to eliminate these foods from your diet. However, long, restrictive elimination diets may not be the answer and can cause harm.
Cutting out multiple food groups for extended periods can lead to nutritional gaps, unnecessary anxiety around eating, and ironically, further disruption to the very microbial diversity you're trying to protect. If you suspect specific triggers, it’s worth consulting with a registered dietitian for a nutritional analysis and professional guidance. You may want to prepare for this appointment by keeping a simple food-and-symptom diary: noting what you eat alongside your pain, energy, and digestion over a few weeks. This gives you real, personal data to discuss with a clinician or dietitian.
Which dietary patterns have the most support?
Rather than rigid rules, the most consistent evidence points toward broad patterns to build towards over time:
● Fibre diversity and plant variety. Large-scale microbiome research (the American Gut Project) found that people eating around 30 different plant foods a week — vegetables, fruit, wholegrains, legumes, nuts, seeds, herbs, and spices — had meaningfully more diverse gut microbiomes than those eating fewer than 10. Diversity of plants, not volume, seems to be what matters.
● Fermented foods. Foods like yoghurt, kefir, sauerkraut, and kimchi introduce live microbial cultures and have been linked to improved microbial diversity in early research.
● Mediterranean-style eating. A randomised controlled trial in people with fibromyalgia found that a personalised Mediterranean-style diet led to meaningful improvements in pain, disability, fatigue, and anxiety scores over eight weeks, compared with a general balanced diet.
● Adequate protein and hydration, which support tissue repair and healthy digestion more broadly.
For practical, food-specific guidance, our related articles on the top 10 foods that make pain worse, expert grocery tips, and how to boost your nerve health go into more practical detail.
Do probiotic supplements help?
Probiotics and prebiotics are often used interchangeably, but they're different things. Probiotics are live microorganisms, usually specific bacterial strains, taken as a supplement or in fermented foods. Prebiotics are types of fibre that feed the beneficial bacteria already living in your gut.
The evidence for probiotics in conditions like IBS shows real but modest benefit, and importantly seems to be strain-specific. Certain individual strains have shown consistent improvements in symptoms like abdominal pain and bloating across trials, while many others show little effect, and results don't necessarily apply across a whole product category simply because it's labelled “probiotic.” Research in fibromyalgia specifically remains more limited and mixed, with small trial sizes and varying strains making it hard to draw firm conclusions.
If you're considering a probiotic supplement, it's worth discussing this with your doctor or dietitian first, particularly if you're on regular medication, as interactions and appropriate strain selection are important.
What else shapes your microbiome besides food?
Diet gets most of the attention, but it's only one influence among several:
● Sleep quality and regularity. Poor or irregular sleep is linked to reduced microbial diversity, and the relationship runs both ways — see our guide to sleep management for pain.
● Stress and sustained cortisol exposure. Chronic stress alters gut motility and microbial balance; you can read more in does stress make pain worse.
● Physical activity. Regular movement is independently associated with greater microbial diversity, separate from its other well-known benefits for pain and digestion.
● Antibiotic and medication history. Antibiotics can significantly reduce microbial diversity, and full recovery of the microbiome can take weeks to months afterwards.
How long before you would notice a difference?
Patience is important. While the microbiome itself can begin shifting within days of a dietary change, meaningful symptom change tends to take weeks rather than days. Most of the supporting research measures outcomes at four, eight, or twelve weeks, not overnight.
Rather than tracking pain scores alone, it's more useful to also notice energy levels, digestion, sleep quality, and general function over this period. Importantly, dietary and lifestyle change should sit alongside your existing medical treatment, not replace it.
Where nutrition fits in a broader pain plan
Diet is a meaningful lever for many people living with chronic pain, but it is one of several strategies that may be useful, not a standalone solution. The strongest outcomes tend to come from a multidisciplinary approach that considers the role of diet in pain management alongside movement, sleep, psychological support, and appropriate medical treatment together, rather than any one piece in isolation.
If you're thinking about making significant dietary changes, it's worth having that conversation with your care team first, especially if you're managing a chronic pain condition alongside other medication or health considerations. Our team would be glad to help - speak to one of our registered dietitians to build an approach that's realistic, personalised, and works with the rest of your treatment plan.