Gluten, a protein found in wheat, barley and rye, arrived with the advent of agriculture 12,000-odd years ago. Considering the first humans are about 2.8 million years old, it is a comparably new addition to our diet.

One common argument against gluten is that we have not had time adapt to this dietary change – some say it takes about 40,000 years.

Exposure to gluten then, irritates our intestines and leads to general lethargy and bloating, an intolerance or coeliac disease.

This is how the saying goes.

"Most of these assertions, however, are contradicted by significant evidence, and distract us from our actual problem: an immune system that has become overly sensitive," counters science writer and author Moises Velasquez-Manoff in a new feature in the New York Times.

As far as the adaptation argument goes, population growth is making genetic change occur at a faster rate. About 100 times faster.

"We are more different genetically from people living 5000 years ago than they were different from Neanderthals," anthropologist John Hawks has said.

This is apparent in the way we have developed a tolerance for dairy within 7000 years.

"Usually, the gene encoding an enzyme named lactase – which breaks down lactose sugars in milk – shuts down after infancy; when dairy became prevalent, many people evolved a mutation that kept the gene turned on throughout life," explains an article in Scientific American.

It stands to reason that, if most of us have adapted to dairy, we should also have adapted to wheat.

"If eating wheat was so bad for us, it's hard to imagine that populations that ate it would have tolerated it for 10,000 years," Sarah A. Tishkoff, a geneticist at the University of Pennsylvania who studies lactase persistence, told the New York Times.

Arguments about whether the "gluten" problems come from eating more gluten or whether gluten-free diets are intrinsically better also lack substance.

Gluten content has also not necessarily increased in wheat in the past 50 years, according to one analysis.

Our wheat consumption has fluctuated, but we are eating about 30 per cent fewer grains than four years ago.

"People buy gluten free biscuits thinking they are healthier – and probably then eat more of them 'guilt free' as they think they are a healthier treat," says dietitian Joanna McMillan.

"When people tell me they have lost weight after giving up gluten I understand why – they are not eating a whole load of energy-dense discretionary foods like cakes, biscuits, doughnuts, croissants and so on. Were they simply to choose gluten-free versions they wouldn't lose weight at all."

Weight-aside, the gluten-free alternatives are not necessarily healthier either, McMillan says.

"Many gluten free products have a higher GI as they are based on potato and rice flour – so unless you really require gluten free (and coeliacs need a strict gluten-free diet) these products are not as healthy as the wholegrain varieties."

And while it is assumed gluten is the problem in the first place, various studies have found this is not always the case.

About 80 per cent of people who avoid gluten (not including those with coeliac disease, which is about 1-2 per cent of the population), do so because of bowel pain, bloating or irritable bowel syndrome (IBS), explains Dr Jane Muir of Monash University.

"A study we published in 2013 we looked at this in more detail in a well designed study [randomised, placebo-controlled, cross-over rechallenge study] – we found no evidence that gluten induced the symptoms in people who believed that they were 'gluten intolerant' and who did not have coeliac disease," Muir says.

Rather they found that a short-chain carbohydrate called FODMAPS, which are also found in non-gluten food like onions and garlic, were causing the symptoms.

All of this isn't to say that coeliac disease – where the immune system reacts abnormally to gluten – and even gluten-sensitivity aren't on the rise.

It seems they are. But so are other allergies, intolerances and immune-related disorders.

"Perhaps the sugary, greasy Western diet – increasingly recognised as pro-inflammatory – is partly responsible," argues Velasquez-Manoff.

"Maybe shifts in our intestinal microbial communities, driven by antibiotics and hygiene, have contributed. Whatever the eventual answer, just-so stories about what we evolved eating, and what that means, blind us to this bigger, and really much more worrisome, problem: The modern immune system appears to have gone on the fritz.

"Maybe we should stop asking what's wrong with wheat, and begin asking what's wrong with us."