How much gluten is safe for coeliacs?

Posted on September 29, 2011

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Currently the only treatment for coeliac disease is a strict lifelong gluten free diet. However several studies have shown that bowel damage persists in a significant proportion of treated coeliac patients even though their symptoms are resolved. Accidentally or deliberately, they must be consuming small amounts of gluten.

One study of coeliac patients’ intestines had to reject 4 of their 49 volunteers because their intestines were abnormal. Led by Professor Alessio Fasano from the University of Maryland, the study fed coeliac patients tiny amounts of gluten as pills. They were tested for bowel damage by biopsy before and after the three month gluten challenge. Fasano’s team found that most patients had no symptoms on 50mg of gluten per day, and blood tests for coeliac antibodies didn’t show any effects either. But 50mg of gluten did cause damage to the patients’ small intestines. Damage to the small bowel is what leads to the risks of osteoperosis and cancer in coeliac patients.

1/100th of a slice of bread is the size of one of the small pieces (circled)

Fasano’s study tells us that 50mg of gluten per day damages the bowel of coeliacs, even though it doesn’t cause symptoms or show up in blood tests. That’s about as much gluten as 1/100th of a slice of standard wheat bread contains. A normal western diet contains 10–20g of gluten each day, which is 200–400 times the minimum amount of gluten that damages the small intestine of a coeliac patient. Fasano’s work also showed that there is a lot of variation between coeliac patients, and some experienced symptoms with as little as 10mg of gluten daily.

A gluten free diet should prevent damage to coeliac patients’ intestines and allow their guts to heal. But it turns out that very few adult coeliacs recover completely. Fewer than 10% of coeliac patients achieve normalistion of their small bowels, according to a study led by Professor Alberto Lanzini at the University of Brescia. The study saw remission in 65% of coeliacs, but 26% had no change to their small intestines after they changed to a gluten free diet. Even though their symptoms had disappeared and blood tests were normal, their small intestines were still being attacked by their immune cells.

It’s likely that the coeliacs in these studies were consuming small amounts of gluten, either as contamination, or deliberately. Both studies make recommendations about how gluten free food should be labelled. In Australia, the gluten free label is used for foods with less then 5ppm gluten, but in Europe the standard is 20ppm. Twenty parts per million doesn’t sound like much, but considering the total amount of food you eat each day it adds up. The two studies calculate that coeliacs could eat 400–500g of wheat substitutes (gluten free breads, cereals, pastas, etc) each day. At 20ppm this woud be 20mg of gluten per kilo, or 10mg in 500g. In other words it would be possible for a coeliac to consume up to 10mg of gluten in a day by eating foods labelled as gluten free. And 10mg of gluten is around the threshold that causes a reaction in some patients. That’s strong support for the strict 5ppm regulation on gluten free foods in Australia.

References for the studies described
Catassi, C., Fabiani, E., Iacono, G., D’Agate, C., Francavilla, R., Biagi, F., Volta, U., Accomando, S., Picarelli, A., De Vitis, I., Pianelli, G., Gesuita, R., Carle, F., Mandolesi, A., Bearzi, I. & Fasano, A. (2007). A prospective, double-blind, placebo-controlled trial to establish a safe gluten threshold for patients with celiac disease. The American journal of clinical nutrition 85, 160-6.

Lanzini, A., Lanzarotto, F., Villanacci, V., Mora, A., Bertolazzi, S., Turini, D., Carella, G., Malagoli, A., Ferrante, G., Cesana, B. M. & Ricci, C. (2009). Complete recovery of intestinal mucosa occurs very rarely in adult coeliac patients despite adherence to gluten-free diet. Alimentary pharmacology & therapeutics 29, 1299-308.
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