Unless you have coeliac disease, where digested gluten irritates your small intestine, you might be putting subjecting yourself to unintended health risks by switching to a gluten-free diet, new research has found.
Going gluten-free has become a popular lifestyle choice among those who want to improve their health, but it won't reduce your risk of heart disease, and may limit the amount of beneficial whole grains you eat.
"Our findings show that gluten restriction has no benefit, at least in terms of heart health, for people without coeliac disease," says one of the researchers, Benjamin Lebwohl from the Columbia University Medical Centre.
For those who do have coeliac disease, the irritation caused by the gluten protein (found in wheat, barley, and rye) can block the uptake of nutrients from the small intestine. Long-term, the problem can lead to heart disease, anaemia, and osteoporosis.
This irritation and associated health issues can be avoided with a gluten-free diet, but if you don't have coeliac disease, cutting out gluten doesn't appear to have the same heart-healthy effects.
Lebwohl and his colleagues came to this conclusion by analysing survey responses from 110,017 non-coeliac people taken over the years 1986 to 2010. The participants were split into five groups, based on the amount of gluten they ate.
It turns out that the risk of a heart attack wasn't significantly different between the group that ate the most gluten and the group that ate the least.
In fact, the researchers say the risk of heart disease could actually be greater with a gluten-free diet – not because of a lack of gluten, but because going gluten-free tends to reduce the number of whole grains you eat as well, which are known to boost heart health.
So if you're determined to go gluten-free, don't expect a reduced risk of heart problems, and make sure you're not reducing the whole grains in your diet at the same time.
"Based on our data, recommending a low-gluten diet solely for the promotion of heart health does not appear warranted," says one of the researchers, Andrew Chan from the Harvard Medical School.
This isn't the first study to question the benefits of going gluten-free for otherwise healthy people, and some experts say it has no benefits at all, despite popular perceptions.
Again, the increased risk may have been because of a food linked to gluten, not gluten itself – in this case, cereal fibres, which are known to protect against this type of diabetes.
So why are so many non-coeliac people swearing by their gluten-free diets?
Gluten consumption has been linked to the production a molecule called zonulin, which can trigger inflammation in the gut, and many people report feeling better after giving it up.
But as we reported last year, whether the positive feelings are down to the gluten-free effect or just an all-round improved diet isn't clear, and some experts think the benefits could be all in our heads rather than our stomachs.
It's fair to say that we've still got plenty to learn about how gluten affects the body, and the knock-on effects that a gluten-free diet might have, whatever your opinion on the debate.
Lebwohl and his team now want to look at gluten intake measured against cancer and autoimmune disease, among other health problems, to get more answers.
"Despite the relatively low prevalence of coeliac disease and non-coeliac gluten sensitivity, surveys suggest that about one-third of Americans are trying to cut down on gluten," says Lebwohl.
"This certainly benefits companies that sell gluten-free products. But does it benefit the public? That is the question we wanted to answer."
The research has been published in the British Medical Journal.