Is leaky gut real?

A woman in her thirties sits across from her doctor, describing a constellation of symptoms: persistent fatigue, skin flare-ups, and digestive discomfort that seems to follow every meal. The doctor listens, runs the usual tests, and finds nothing conclusive.

The gut lining isn't a solid wall; it's a selectively permeable barrier that regulates what enters the bloodstream. That selectivity is maintained by tight junction proteins between intestinal cells.

Mainstream gastroenterology doesn't use leaky gut as a diagnosis because the evidence linking increased intestinal permeability to those broader symptoms in healthy people isn't strong enough yet. Most doctors trained in conventional medicine were taught to view the gut as a digestive organ, not a systemic one — a distinction that feels increasingly outdated in light of the research but still shapes clinical practice.

Alessio Fasano's research on zonulin in the early 2000s was a turning point. His work showed that zonulin, a protein that regulates tight junctions, is elevated in celiac disease patients and that gluten exposure triggers its release.

If you're trying to support gut barrier health through diet, the most evidence-backed choices are also the most obvious: more fiber from fruits, vegetables, and whole grains; less alcohol; more fermented foods like yogurt and 🥬 kimchi; and less ultra-processed food. Supplements marketed specifically for leaky gut — collagen powders, L-glutamine blends, gut repair protocols — vary hugely in quality and most don't have strong human clinical trial evidence behind them.

If a practitioner is treating you for leaky gut with expensive supplement protocols, ask what clinical evidence specifically supports the intervention for your symptoms. And if you've been on antibiotics, dealing with high stress, or drinking heavily and your gut feels off, pulling back on alcohol and ultra-processed food while adding fermented foods and fiber is the most evidence-aligned thing you can do.

Leaky gut as a biological phenomenon is real. Leaky gut as a wellness catch-all diagnosis for vague symptoms in people who don't have a clear gastrointestinal disease is where the evidence runs out.