GLUTEN'S SUBTLE EFFECT ON THE MIND

Some people say they don’t feel good after eating gluten – but perhaps that is because of its effects on mental health rather than on the gut.

Gluten is a protein found in foods including wheat and rye that causes the negative reaction in coeliac disease, an autoimmune condition affecting about 1 per cent of us. Another 12 per cent of people say they get bloating, tiredness and other symptoms after they eat gluten-rich foods.

But there is no agreement on whether this “non-coeliac gluten sensitivity” is a real condition, particularly because several studies have shown that people who have it report the same symptoms if they eat an inactive substance they think is gluten.

However, even if gluten doesn’t cause gut troubles, it may trigger other symptoms in some people, says Jessica Biesiekierski at La Trobe University in Australia.

Biesiekierski and her colleagues investigated with the help of 14 people with self-reported gluten sensitivity. In one experiment, the participants were asked to eat a yogurt on separate days two weeks apart. On one of the days, the yogurt contained gluten, on the other day it was gluten-free. The participants didn’t know which yogurt was which.

In another experiment, people were given two batches of muffins to eat a few weeks apart. Again, one batch contained gluten and one didn’t, and the volunteers didn’t know which was which.

The volunteers reported similar levels of bloating and cramps regardless of whether they ate the gluten-containing or gluten-free foods, reinforcing previous findings that gluten isn’t responsible for gut upsets in people without coeliac disease.

That wasn’t the only discovery. Participants reported feeling more tired after eating gluten-containing yogurt and reported fewer positive emotions after consuming the gluten-containing muffins than after they ate the gluten-free foods. The effects were small but statistically significant, and may explain why some people say they feel better after going gluten-free, says Biesiekierski, who presented the results at the annual meeting of the Gastroenterological Society of Australia in Brisbane earlier this month.

The findings chime with previous work by Biesiekierski showing that gluten seemed to cause more symptoms of depression than an inactive substance in 22 people with gluten sensitivity. Similarly, a 2015 study led by Antonio Di Sabatino at the University of Pavia in Italy found that gluten caused more symptoms of depression and “brain fogginess” than an inactive substance in 59 gluten-sensitive individuals.

Michael Potter at the University of Newcastle in Australia says the evidence is building. “These studies suggest there are definitely people who have reproducible mental health responses to gluten when they undergo blinded challenges.”

Even if gluten can directly affect mental health, it is likely to occur in only a few sensitive people, says Biesiekierski. “We’re certainly not saying that everyone will get depression after eating gluten,” she says.

Written by Alice Klein in "New Scientist", UK, volume 239, n. 3196, September 22-28 2018, excerpts p.15. Digitized, adapted and illustrated to be posted by Leopoldo Costa.