Leaky gut is one of those terms where conventional and functional medicine talk past each other. Conventional medicine often dismisses it as wellness-industry nonsense. Functional medicine often uses it as the explanation for almost everything. Both positions are wrong.
The honest clinical answer is that increased intestinal permeability is a real, measurable physiological state. Whether it is causing your specific symptoms is a different question that requires actual investigation, not assertion.
What the science actually says
The intestinal lining is a single layer of cells held together by tight junctions. Those junctions can loosen under stress, inflammation, certain medications, alcohol, and specific microbial signals. When they loosen, larger particles can cross from the gut into the bloodstream.
This phenomenon has a clinical name: intestinal permeability. It is measured by the lactulose-mannitol test, by serum zonulin levels, and by markers like LPS-binding protein.
The phenomenon is established in:
- Celiac disease (well-characterized, reversible with gluten removal)
- Inflammatory bowel disease (Crohn's, ulcerative colitis)
- Type 1 diabetes
- Some autoimmune conditions
- After significant alcohol use
- After NSAID use
- Under severe physiologic stress (sepsis, burns, surgery)
In these contexts, intestinal permeability is real, measurable, and clinically relevant. It is not controversial.
Where the controversy lives
The controversy is about a broader claim: that increased intestinal permeability is a primary driver of fatigue, brain fog, food sensitivities, skin issues, joint pain, and many other diffuse symptoms in patients without the diagnoses above.
The honest position:
Some of this is likely true. Sub-clinical intestinal permeability probably drives or worsens chronic inflammatory symptoms in a meaningful fraction of patients. The mechanism is plausible and the early evidence supports it.
Some of it is overclaimed. Not every symptom in every patient is gut-driven. Diagnosing leaky gut by symptom rather than by data is sloppy. Treating it without a panel is guesswork.
The marketing has outrun the science. The wellness industry has built a business selling leaky gut protocols to anyone with vague symptoms. Most of those products are not necessary, and some of them are actively unhelpful.
How I work this clinically
When a patient suspects intestinal permeability is driving their symptoms, I do not affirm or dismiss the hunch. I check.
The workup:
- Comprehensive stool panel. Markers of inflammation (calprotectin), barrier integrity (zonulin if available), and microbial composition. Often answers most of the question.
- Metabolomics panel. Surfaces inflammatory markers and microbial metabolites that suggest barrier compromise.
- Food sensitivity testing. IgG/IgA pattern across 200+ foods. Useful when food triggers seem to be part of the picture.
- Standard inflammatory markers. hsCRP, ferritin, ESR.
- Rule out the conventional diagnoses. Celiac panel, sometimes IBD workup.
The pattern across these tells me whether intestinal permeability is part of the case and which intervention will move it.
What the intervention looks like
When the panel supports the diagnosis, the intervention is structured.
Remove the drivers:
- Alcohol, especially daily
- NSAIDs, when alternatives are available
- Gluten if the panel suggests reactivity
- Other specific food triggers from the IgG/IgA panel
- Chronic stress, addressed with structured downregulation
Heal the barrier:
- L-glutamine, often the highest-leverage single supplement
- Zinc carnosine
- Aloe vera, slippery elm, marshmallow root (mucosal soothing)
- Sometimes specific peptides (BPC-157) when the case calls for it
Rebuild the microbiome:
- Daily fermented foods and adequate fiber
- Targeted probiotics based on the panel
Address the gut-immune dialogue:
- Bone broth or collagen for amino acids the lining needs
- Glycine, often short in adults
Six to twelve weeks of this protocol usually shifts the panel and the symptoms together.
What I do not do
I do not diagnose leaky gut from symptoms alone. I do not prescribe protocols without the workup. I do not sell branded products. If your case calls for it, the path in is the Precision Call. I will tell you what I see.
