07/30/2026
Most people think gluten is only a problem if you have coeliac disease or a diagnosed sensitivity.
However, every single human being mounts an inflammatory response to gluten, regardless of whether they ever feel a symptom.
What Actually Happens When You Eat Gluten:
When gluten enters the small intestine, it triggers the release of a protein called zonulin in every human digestive system, without exception. Zonulin was discovered by gastroenterologist Dr Alessio Fasano and his research team, and it is one of the most significant findings in gut health research of the past two decades.
Zonulin acts as a gatekeeper of the tight junctions between the cells lining your intestinal wall. These tight junctions are meant to be selective, allowing nutrients through while keeping larger molecules, bacteria, and undigested food particles out of the bloodstream.
When zonulin is released, it temporarily loosens these tight junctions. In a healthy gut with good resilience, they tighten back up again relatively quickly. In a gut that is already compromised by stress, nutrient depletion, dysbiosis, or frequent gluten exposure, those junctions may stay loose for longer, or become chronically loosened over time.
This is the mechanism behind what is commonly called intestinal permeability, or leaky gut.
Why This Matters for the Thyroid:
🦋 Gliadin, one of the proteins in gluten, has a molecular structure that closely resembles thyroid tissue. When immune cells are activated in response to gluten crossing the gut wall, there is a risk of those immune cells also attacking thyroid tissue through a process called molecular mimicry
🦋 This molecular mimicry is considered one of the contributing mechanisms in the development and progression of Hashimoto's thyroiditis and Graves disease
🦋 A chronically permeable gut allows lipopolysaccharides (bacterial fragments) and other inflammatory molecules into circulation, which drives systemic inflammation and can further suppress thyroid hormone conversion in the liver
Why the Effects Are So Different Between People:
🦋 Someone with a diverse, robust gut microbiome recovers quickly from the zonulin response, with tight junctions closing again efficiently
🦋 Someone with pre-existing gut dysbiosis, nutrient deficiencies, chronic stress, or a history of antibiotic use may have structurally weaker tight junctions that take much longer to recover, or do not recover fully between exposures
🦋 Genetics play a role in how strongly the immune system responds to gliadin specifically, with certain HLA gene variants associated with a much more aggressive immune reaction
🦋 Other co-existing factors like alcohol consumption, non-steroidal anti-inflammatory drug use, and chronic psychological stress all independently loosen tight junctions, compounding the effect of gluten
This is why two people can eat the same meal and one feels fine while the other does not. It is not that one person is reacting and the other is not. It is that one person's gut has far more capacity to absorb the hit.
Food Sources That Support Gut Barrier Integrity
🦋 Bone broth contains collagen, gelatin, and glutamine, all of which support the structural integrity of the gut lining. Aim for one to two cups daily if gut healing is a priority
🦋 Zinc-rich foods such as pumpkin seeds, oysters, beef, and chickpeas support tight junction protein synthesis. Daily requirement is approximately 8mg for women and 11mg for men
🦋 Vitamin D, found in fatty fish like salmon and sardines, eggs, and liver, plays a direct role in regulating zonulin production. Daily requirement is 1,500 to 2,000 IU for maintenance, though many thyroid patients are depleted and may need more under practitioner guidance
🦋 Quercetin-rich foods such as capers, red onion, apples, and green tea have been shown in research to help stabilise tight junctions and reduce zonulin release
🦋 L-glutamine, found in meat, fish, eggs, dairy, and legumes, is the primary fuel source for intestinal lining cells and supports repair of a compromised gut wall
Action Steps:
🦋 Consider trialling a strict gluten-free period of at least 60 to 90 days if you have Hashimoto's or Graves disease and have not yet explored this. Partial reduction is unlikely to give you a clear picture
🦋 If you have ongoing gut symptoms alongside thyroid dysfunction, ask your practitioner about testing zonulin levels, intestinal permeability markers, or a comprehensive stool analysis
🦋 Keep a symptom diary when making dietary changes, tracking energy, digestion, brain clarity, and mood, since improvements can be gradual and easy to miss without a record to compare
Gluten does not affect everyone the same way, but it does affect everyone.
