Only one in six people who claim to be gluten-intolerant actually are, new Australian research suggests.
Gluten-free diets have become increasingly popular in recent years, but pose risks for people who aren't truly intolerant.
Around 7 to 8 percent of adult Australians claim to suffer bloating and other symptoms associated with coeliac disease.
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But much of it could be all in the mind. When they don't know if what they're eating contains gluten or not, only 1 percent of adults actually had a reaction to food containing the wheat protein.
"Many Australians are believed to monitor and limit their intake of gluten despite having no formal diagnosis of coeliac disease," the study, published in the Medical Journal of Australia, reads.
This is a health risk on its own, the authors say, because "gluten-free products are not necessarily equivalent to their gluten-containing counterparts regarding their macronutrient and micronutrient content".
"Several studies have demonstrated that gluten-free diets may not provide adequate amounts of trace elements and vitamins such as calcium, vitamin D, folate, thiamine, riboflavin and niacin.
"A gluten-free diet may adversely affect cardiovascular risk factors such as total cholesterol levels, weight gain leading to obesity, glucose tolerance and blood pressure, and may lead to development of the metabolic syndrome."
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Gluten-free diets also cost around 17 percent more than normal diets, the University of Newcastle researchers noted.
"When there's this industry out there - celebrity chefs touting a gluten-free diet - people take it on as something that's beneficial for their health," lead researcher Michael Potter told The Australian.
"There's very little evidence to suggest it's good for people who don't have coeliac disease."
But co-author Marjorie Walker said there could be "a real immune action" scientists haven't quite figured out yet that's causing people to avoid gluten, even if there are no symptoms of coeliac disease when they're not aware what they're eating contains gluten.
"It may be that the doctors haven't quite got it right yet, rather than the patients," she told the paper.