The existence of increased intestinal permeability is scientifically recognised and the associations with various diseases are consistent across review studies. The evidence base is largely associative, however: whether leaky gut causes diseases or is a consequence of them remains unclear. Practically speaking, a Mediterranean dietary pattern and avoiding known risk factors such as alcohol and processed food offer the best starting points, while specific supplements still have too little clinical evidence to support them.
Leaky gut, known in science as 'increased intestinal permeability', is a recognised biological phenomenon. The intestinal wall is made up of cells that sit tightly against one another via so-called 'tight junctions' -- molecular locks that prevent harmful substances from reaching the bloodstream. When those locks loosen, bacterial waste products and inflammation-promoting substances such as lipopolysaccharide (LPS) can pass through after all. Multiple review studies recognise this mechanism as real, although not everything about it has been fully explained yet.
What causes leaky gut is fairly well understood: a high-fat diet, excessive alcohol consumption, chronic stress, antibiotic use and an imbalance in gut bacteria (dysbiosis) all damage the intestinal barrier. In people with obesity or type 2 diabetes, researchers observe that beneficial gut bacteria that produce short-chain fatty acids decline, while bacteria that fuel inflammation increase. SARS-CoV-2 can also directly damage intestinal cells and thereby increase gut permeability, although that evidence is more limited and based on fewer studies.
Leaky gut is linked in multiple studies to a range of diseases: obesity, type 1 diabetes, non-alcoholic fatty liver disease, cardiovascular disease and autoimmune conditions such as multiple sclerosis and rheumatoid arthritis. An important nuance is needed here: these are almost always observed associations, not proven causal relationships. Whether leaky gut causes these diseases, or is instead a consequence of the underlying condition, has not yet been established. Chicken-and-egg debates are the norm in this field, not the exception.
What can you do about it yourself? The Mediterranean diet, rich in vegetables, fruit, fish, nuts and poultry, is associated with a more diverse and healthier gut microbiome. Probiotics, prebiotics and synbiotics show promising effects on restoration of the intestinal barrier in review studies. Omega-3 fatty acids and vitamins A, B, C, D and E are also positively linked to intestinal barrier function in the literature. The strength of evidence for all these interventions is limited, however: these are not large clinical trials but review studies. There is therefore reason for cautious optimism, but no proof that a specific supplement or diet reliably restores leaky gut in humans.
A small study with 43 participants and no placebo group investigated a herbal formula containing curcumin, aloe vera, glutamine and similar substances. The results appeared positive: permeability normalised in most participants and gastrointestinal complaints decreased substantially. Because of the small group size and the absence of a control group, these results are not conclusive. Until larger, controlled studies are available, it is too early to recommend this formula.
Based on multiple review studies and a small clinical study (n=43, no placebo group). No large independent RCTs among the sources. Causality has not been demonstrated for most of the associations.