Too many people are on a gluten-free diet

Best-selling books tout gluten as the main source of health problems affecting everything from the brain to the belly. It's the topic of cartoons and fodder for late-night comedy shows. Movie stars, television personalities and major sports figures all sing the praises of a gluten-free diet.

They say it makes them feel healthier, stronger and even happier. The gluten-free diet has now surpassed all others searched for on Google in the United States, beating the Atkins and Paleolithic diets.

And yet, there is little scientific evidence to support these claims. People seem to be drawing wild conclusions from the fact that those who suffer from coeliac disease must cut every trace of gluten out of their diet, deciding illogically that if cereal grains such as wheat, rye and barley are harmful to a small slice of the population, then they must be harmful to everyone.

The association with coeliac disease seems to give the gluten-free diet more medical legitimacy than other diets.

Coeliac disease occurs in about one per cent of the population. Those who develop it mount an immune reaction to gluten resulting in inflammation in the small intestine and malabsorption of nutrients.

For those with coeliac disease, gluten is toxic. But for the vast majority who don't have the disease, it may actually be detrimental to eliminate it. A gluten-free diet frequently lacks fibre.

And while wheat flour is enriched with vitamins and iron, non-gluten containing flours are not fortified. As a result we see people on a gluten-free diet who are vitamin deficient. Many gluten-free products also have added sugar and fat to ensure palatability, which can cause weight gain.

Of course a gluten-free diet is also socially inconvenient and requires vigilance.

Not only are staples such as pasta, bread and beer off limits, but wheat flour and vital gluten are often added to products such as seasoning and sauces, soy sauce and sushi, candies and dietary supplements.

Some physicians and nutritionists recommend a gluten-free diet to prevent autoimmune diseases, reduce inflammation, to treat depression and fatigue or for those with autism.

None of these indications have a scientific basis. Nor is it true that removing gluten from one's diet increases energy, as is often claimed. One study of competitive cyclists found that a gluten-free diet did not increase energy output.

All that said, there are individuals with irritable bowel syndrome who improve on a gluten-free diet, in the absence of coeliac disease. These people appear to have a gluten or wheat sensitivity. But the number of people who have non-coeliac wheat sensitivity is unclear.

At any rate, it is a small percentage of those who have adopted the diet. Most people who believe that they are wheat-sensitive, without medical confirmation, are probably not.

The gluten-free food industry now occupies a multibillion-dollar niche, so who knows how long this trend will last? 

We wish we could at least say that gluten-free diets are perfectly harmless, if not particularly helpful. But that's not what the evidence suggests.

What gluten-free faddists don't seem to realise is that in excluding gluten, they're also excluding a host of nutrients that keep them out of the doctor's office, not in it.

Peter Green is director of the Celiac Disease Center at Columbia University. Rory Jones is adjunct professor of Narrative Medicine at Barnard College. 

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