‘Leaky gut’ gets used a lot — sometimes dismissively, sometimes as an explanation for everything. The reality sits somewhere in the middle. It describes a genuine physiological process called increased intestinal permeability, and while it isn’t a diagnosis in the conventional sense, it’s a useful way of thinking about what happens when the gut barrier isn’t doing its job properly.
The gut lining is designed to be selectively permeable — letting nutrients through while keeping larger, potentially inflammatory compounds out. When that selectivity breaks down, the immune system gets more exposure to things it wasn’t meant to encounter in circulation. That can trigger a cascade of effects that, for some people, shows up well beyond the digestive system.
What's actually happening in the gut
The intestinal lining is a single layer of cells connected by structures called tight junctions. Think of these as the gatekeepers — they regulate what passes through and what doesn’t. When the gut is repeatedly irritated or inflamed, those junctions become less tightly regulated, which means the barrier becomes more permeable than it should be.
This isn’t about literal holes in the gut wall. It’s more subtle than that. What changes is the level of selectivity — and that shift can increase the immune system’s exposure to partially digested food proteins, bacterial fragments like endotoxins, and inflammatory compounds produced during dysbiosis.
Over time, that increased exposure can contribute to a state of low-grade systemic inflammation and heightened immune reactivity — which is where the wider effects start to appear.
How it shows up beyond digestion
Because the gut is so tightly connected to the immune system, the nervous system, and hormonal regulation, increased permeability can influence things that seem unrelated at first glance. This is one of the reasons leaky gut can be difficult to recognise — the symptoms aren’t always obviously digestive.
Digestive symptoms
The most direct effects are in the gut itself: bloating, abdominal discomfort, food sensitivities, and unpredictable bowel habits. These symptoms often overlap with IBS, and in many cases, increased permeability is part of what’s driving the reactivity.
Immune and inflammatory effects
Around 70% of the immune system is located in and around the gut. When the barrier is compromised, immune activity tends to increase — sometimes in ways that feel unpredictable. Flares that seem unconnected to food, heightened sensitivity to environmental triggers, and a general sense of the immune system being on edge can all be downstream effects.
Skin and respiratory patterns
The gut-skin connection is increasingly well-recognised. Conditions like eczema, rosacea, and acne can flare in response to gut inflammation, as can histamine-type reactions and sinus congestion. These aren’t inevitable consequences of leaky gut, but they’re common enough to be worth considering when the gut isn’t functioning well.
Energy, mood, and cognition
The gut-brain axis is a two-way street. When gut inflammation is elevated or the microbiome is significantly disrupted, it can affect neurotransmitter production, stress signalling, and the quality of sleep. Fatigue, brain fog, low mood, and poor stress tolerance are all things people report improving when their gut health improves — even when those symptoms didn’t seem gut-related at the time.
Hormones and metabolism
Gut health intersects with hormonal regulation in a few important ways. The microbiome plays a role in oestrogen metabolism; constipation slows clearance of hormone metabolites. Blood sugar regulation and cortisol patterns can both be affected by chronic gut inflammation. These connections aren’t always obvious, but they matter — particularly for people whose hormonal symptoms don’t respond well to direct interventions.
What tends to drive it
This is where functional medicine becomes particularly useful — not just identifying that barrier function is compromised, but working out what’s keeping it that way. The same interventions don’t work for everyone, because the drivers differ.
Common contributors include:
- Chronic stress and poor sleep — both can alter gut motility, immune balance, and the integrity of the gut lining directly
- Dysbiosis and SIBO — microbial imbalance increases fermentation and irritation that keeps the barrier inflamed
- Alcohol — even moderate regular intake can worsen permeability and inflammation over time
- Ultra-processed foods and low fibre intake — reduce the diversity and resilience of the microbiome
- Individual food triggers — commonly gluten, dairy, or high-histamine foods, but highly person-specific
- Medications — NSAIDs in particular can irritate the gut lining with regular use
- Post-infectious changes — acute gastroenteritis can sometimes precede longer-term gut reactivity
Identifying which of these is most relevant shapes which strategies are likely to actually help.
Management strategies that work
The most effective approach is structured and phased. Trying to do everything at once — gut lining supplements, probiotics, elimination diets, stress management — tends to create noise rather than clarity. A more useful framework is: reduce what’s irritating the gut, address the root drivers, then rebuild resilience.
Step one: reduce ongoing irritation
Before anything else, the goal is to create a calmer baseline. That usually means cutting back on alcohol and ultra-processed foods, stabilising blood sugar with protein and fibre at each meal, and — where there’s a clear pattern — a short-term trial removing a suspected trigger like gluten or dairy. Bowel regularity matters here too; slow transit keeps the gut exposed to inflammatory compounds for longer.
This phase isn’t about dietary perfection. It’s about lowering the inflammatory load so the gut has a chance to start recovering.
Step two: address the root drivers
If dysbiosis, SIBO, or digestive insufficiency is present, the gut barrier won’t repair properly until those are addressed. This is often why people who take gut-lining supplements for months see limited results — the barrier is being patched while the underlying irritation continues.
Functional medicine here focuses on meal timing and motility, supporting digestion upstream (stomach acid, enzymes, bile), and investigating persistent symptoms with appropriate testing when it will actually change the treatment plan.
Step three: rebuild the microbiome and gut barrier
Once the main drivers are under control, the focus shifts to rebuilding. That means increasing plant diversity gradually, introducing fermented foods carefully (they’re helpful for many people, but can be overstimulating when the gut is still inflamed), prioritising nutrient-dense eating, and using targeted gut-lining support where appropriate.
Gradual is the operative word. A gut that’s been reactive for a long time doesn’t respond well to aggressive intervention — pacing matters.
Step four: support the nervous system
Gut barrier function is directly influenced by the nervous system — stress affects motility, immune balance, and the tight junctions themselves. For many people, this is the step that makes the other three actually stick. Sleep consistency, regular gentle movement, breathwork or mindfulness practice, and addressing anxiety around food and symptoms all contribute to the kind of nervous system regulation that supports gut healing.
It’s not a soft add-on. For people under chronic stress, treating the nervous system as central to the plan — rather than optional — tends to change outcomes.
How long does improvement take?
It depends on how long symptoms have been present and how many drivers are involved. Some people notice meaningful improvement within a few weeks once the main triggers are removed and digestion is properly supported. Cases involving long-standing dysbiosis, chronic stress, or SIBO typically need a structured plan over several months, with reassessment built in along the way. There’s no universal timeline, but gradual and consistent tends to win over fast and aggressive.
A final note
Leaky gut is better understood as a signal than a diagnosis — a sign that the gut barrier is under pressure and that other systems are likely feeling the effects. The symptoms it contributes to are real and can be wide-ranging, but they’re also responsive to the right approach. Identifying what’s driving the barrier disruption, addressing it in a structured way, and rebuilding resilience over time gives the gut what it needs to actually recover — rather than just managing symptoms indefinitely.
This article is for educational purposes only and is not a substitute for personalised medical advice. If you have severe symptoms, blood in stool, unexplained weight loss, persistent fever, or significant anaemia, please seek medical evaluation. Please reach out to us at the clinic if you need support https://londoncfm.co.uk/contact/
