Gluten-free diets are getting more and more popular for people who want to lose weight, but new research has found that they may not actually be that healthy.
Any weight loss and reduction in tummy pain are due to eating more vegetables and other fibre-rich foods, – rather than cutting out the protein itself – say scientists.
An increasing number of people are choosing a gluten-free lifestyle – even though they are not allergic to the sticky substance found in cakes and bread.
Now a study has shown the diet can help modest slimming and combat bloating and discomfort, but most of the benefits may be driven by eating more by replacing wheat, rye and other grains with vegetables, brown rice, corn, oats and quinoa.
The researchers, whose findings were published in the journal Nature Communications, said this boosts good bacteria in the gut that staves off inflammation and illness.
Senior lead investigator Professor Oluf Pedersen, of the University of Copenhagen in Denmark, said: By now we think our study is a wake-up call to the food industry.
Gluten-free may not necessarily be the healthy choice many people think it is.
For the study, 60 healthy middle-aged Danes were assigned randomly to two eight-week diets – one low in gluten, at 2g a day, and the other high in gluten, at 18g a day.
They had a break in between of at least eight weeks when they consumed an average 12g of gluten daily.
In comparison with the high-gluten regime, the low one induced moderate changes in the intestinal microbiome – or gut bacteria – and reduced self-reported bloating.
But during this the participants ate more dietary fibres – which the researchers think were responsible for the effects.
Professor Pedersen said: We demonstrate that, in comparison with a high-gluten diet, a low-gluten, fibre-rich diet induces changes in the structure and function of the complex intestinal ecosystem of bacteria, reduces hydrogen exhalation, and leads to improvements in self-reported bloating.
Moreover, we observed a modest weight loss, likely due to increased body combustion triggered by the altered gut bacterial functions.
Theres been debate about whether low-gluten diets should be advised for people without coeliac disease – a severe immune response to even tiny amounts.
Professor Pedersen and colleagues decided they shouldnt – even though some healthy individuals may prefer it to combat intestinal discomfort or excess body weight.
He said: More long-term studies are definitely needed before any public health advice can be given to the general population.
Especially, because we find dietary fibres – not the absence of gluten alone – to be the primary cause of the changes in intestinal discomfort and body weight.
Most gluten-free food items available on the market today are massively deprived of dietary fibres and natural nutritional ingredients.
Therefore, there is an obvious need for availability of fibre-enriched, nutritionally high-quality gluten-free food items which are fresh or minimally processed to consumers who prefer a low-gluten diet.
Such initiatives may turn out to be key for alleviating gastro-intestinal discomfort and in addition to help facilitating weight control in the general population via modification of the gut microbiota.
The two diets were balanced in number of calories and nutrients including the same amount of dietary fibres. But the composition of the latter differed markedly.
Based on their observations of altered food fermentation patterns of the gut bacteria, the researchers said the effects may not be primarily due to reduced intake of gluten.
A low-gluten diet has previously been proposed to diminish gastrointestinal symptoms in patients with inflammatory bowel diseases and irritable bowel syndrome which occur in up to 20 percent of the Western population.
Last year a US study of more than 110,000 people found a low-gluten diet increased the risk of a heart attack by about 15 per cent.