For people with coeliac disease, gluten can set off a toxic reaction that harms the lining of the guts and kills the little hairs that absorb nutrition.
But gluten-free diets are a trend among non-coeliac sufferers. Coles and Woolworths have entire shelves dedicated to gluten-free foods. Some people, especially women, complain that gluten makes them feel bloated or sluggish.
Yet two studies in Melbourne last year said there is no evidence that gluten is harmful except for a small group of people, the AFR reported.
The studies are a follow-up on research done two years ago that gave clinical evidence that gluten could cause gastrointestinal symptoms in people without coeliac disease. When the American Journal of Gastroenterology published it in 2011, it gave a boost to the gluten-free industry.
Now the journal is reviewing the latest findings in the follow-up study.
Jess Biesiekierski, who completed a PhD at Monash University, based at Eastern Health Clinical School, Box Hill Hospital in Melbourne, is part of the research team. She now says the results she and her team presented two years ago were not concrete.
The tests found no signs such as inflammation or immune response to explain the impact of gluten.
She presented the two follow-up studies late last year at the Australian Gastroenterology Week in Adelaide.
The tests for the follow-up studies were redesigned to see whether it was gluten or something else causing the problems. One test looked at 37 people on a high gluten, low gluten and gluten-free diet. The second test looked at 22 people who were put on gluten or gluten-free diet.
The results showed no gluten-related gastrointestinal symptoms.
Biesiekierski said non-coeliac gluten sensitivity is not yet understood, but may exist. Biesiekierski, a registered nutritionist, is concerned people are self-diagnosing as gluten intolerant and cutting foods with gluten.
Gluten, a type of protein is found in the grains wheat, barley, rye and oats. Avoiding these grains can result in low fibre and insufficient vitamin B.