What a fly screen and your gut have in common.
Jul 07, 2026Intestinal permeability: what "leaky gut" actually means
Intestinal permeability is a real, measurable physiological process, but it is also one of the most misused terms in wellness marketing. This post looks at what the gut lining actually does, what happens when it becomes more permeable than it should be, and where the evidence is solid versus where it is still being worked out.
The gut lining has one job: selective control
The wall of the small intestine is a single layer of cells, held together by structures called tight junctions. Its role is to let nutrients through while keeping out material that has no business entering the bloodstream, including undigested food particles, bacterial fragments, and toxins.
When those tight junctions loosen beyond their normal, adaptive range, larger molecules can pass through the gut wall into circulation. This is what the research literature refers to as increased intestinal permeability. It is a mechanism, not a diagnosis, and it exists on a spectrum rather than as an on or off switch.
What can loosen the tight junctions
A number of factors are associated with increased permeability, including chronic stress, gut dysbiosis, excess alcohol intake, certain medications such as long-term NSAID use, and low-fibre or highly processed diets. None of these act in isolation. Permeability tends to shift gradually, in response to sustained load on the system rather than a single event.
Worth knowing: a certain amount of intestinal permeability is normal and necessary. The gut wall is meant to be somewhat responsive, not a fixed barrier. The concern is sustained, excessive permeability, not the existence of permeability itself.
Why it matters beyond digestion
Once bacterial components such as lipopolysaccharide (LPS) cross into circulation, the immune system responds. This is part of why increased permeability is discussed in relation to low-grade systemic inflammation, and why it shows up in conversations about fatigue, skin conditions, joint discomfort, and mood, alongside digestive symptoms like bloating and irregular bowel habits.
This does not mean every symptom in that list traces back to the gut. It means the gut lining is one plausible contributing factor worth investigating properly, rather than the default explanation for everything.
How it is actually assessed
In a clinical setting, intestinal permeability is approached through a combination of case history, symptom pattern, and where appropriate, functional testing such as zonulin markers or a broader functional blood panel that looks at inflammatory and nutrient markers alongside gut-specific indicators. This is different from a single home test giving a yes or no answer.
Key takeaways
- Intestinal permeability is a real, spectrum-based physiological process, not a fringe theory
- Some permeability is normal; the issue is sustained, excessive permeability
- Diet, stress, alcohol, medications, and gut microbial balance all contribute
- Proper assessment looks at patterns across multiple markers, not one isolated result
Where to start if this sounds familiar
If you are dealing with a cluster of symptoms that do not have a clear explanation, a comprehensive look at what is actually happening inside your gut and immune system is a more useful starting point than guessing based on symptoms alone.
See what's actually going on
The Functional Blood Analysis looks at the full picture, gut, inflammatory, and nutrient markers included, so you are working from data rather than assumptions.
Learn about the FBAThis article is general information, not personal medical advice. If you have ongoing digestive or systemic symptoms, please see your practitioner for individual assessment.
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