People who do not have coeliac disease may still experience gastrointestinal and extra-intestinal symptoms after ingesting products containing gluten, as a result of a weakened intestinal barrier, scientists have found out. This triggers a body-wide inflammatory immune response which may explain why these individuals are in pain, even though gluten consumption does not damage their intestines to the same extent as coeliac disease patients.

Coeliac disease is a severe autoimmune disease characterised by the fact the immune system attacks the lining of the small intestine in response to gluten intake, causing symptoms such as stomach pains, vomiting, constipation or chronic fatigue.

Roughly 1% of the population suffer from it. However, many more individuals have a 'gluten intolerance' – experiencing similar symptoms when they consume gluten without their intestines facing as much damage.

In recent years, there has been much debate about whether gluten intolerance is a real medical condition, and what biological mechanisms are behind it.

Researchers have struggled to determine why some people who lack the characteristic blood, tissue, or genetic markers of coeliac disease experience its symptoms.

In this recent study, published in the BMJ journal Gut, scientists have worked with people in this situation, finding out that gluten intake could be responsible for some form of weakening of the intestinal barrier and a body-wide immune response.

Body-wide or local immune response

The researchers from Columbia University recruited 80 participants who were not diagnosed with coeliac disease but suffered from some of its symptoms. Forty people with coeliac disease and 40 healthy controls also took part.

French bread
Bread contains gluten, the main culprit in coeliac disease Reuters

In coeliac patients, the scientists observed a local immune response in the intestine – characterised by a proliferation of intestinal cytotoxic T cells – which neutralised microbes before they passed through the damaged intestinal barrier. This prevented a systemic inflammatory immune response from being triggered.

In contrast, patients with gluten sensitivity, but no coeliac disease, showed no signs of intestinal cytotoxic T cells. However, researchers identified markers of intestinal cell damage, as well as a body-wide inflammatory immune response.

These findings suggest that patients with gluten intolerance may not suffer from the same intestinal damage as coeliac disease patients, but they still have a weakened intestinal barrier, caused by intestinal cell damage when they eat gluten. This weakened barrier allows microbes to enter the body, triggering a body-wide inflammatory immune response.

This conjunction of a weakened intestine and a systemic immune activation may be behind the symptoms experienced by these individuals, the scientists say.

"Our study shows that the symptoms reported by individuals with this condition are not imagined, as some people have suggested," concludes study co-author Peter H Green, MD, the Phyllis and Ivan Seidenberg Professor of Medicine at CUMC and director of the Celiac Disease Center. "It demonstrates that there is a biological basis for these symptoms in a significant number of these patients."