Intestinal permeabilityLeaky gut
How much passes through the gut lining — real biology, oversold as a diagnosis.
Intestinal permeability describes how readily substances cross the gut lining, which is governed by a barrier of mucus, epithelial cells and their junctions plus local immune defences. 'Leaky gut' is the popular name for increased permeability.
It matters because the biology is genuine and measurable — permeability is altered in conditions such as coeliac and Crohn's disease, and can shift with diet and other stressors — but a review of the human evidence is clear that there is no gold-standard test of gut-barrier function, and that increased permeability has not been established as the cause of the long list of everyday symptoms attributed to it.
In practice, treat 'leaky gut' as a mechanism under investigation, not a diagnosis: commercial tests and 'gut-healing' protocols sold on it outrun the evidence, and persistent gut symptoms deserve proper medical assessment.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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