Near the beginning of the movie This Is The End, Seth Rogen, playing himself, tells his buddy Jay Baruchel, that “he is on a cleanse” and that we should all stop eating gluten. “Whenever you feel sh---y, that’s because of gluten,” Rogen explains. “Gluten is a vague term. It’s something that’s used to categorize things that are bad. Ya know? Calories, that’s a gluten. Fat, that’s a gluten.”

It is a hilarious scene. And it is spot on. It captures the current insanity surrounding gluten and, more broadly, wheat, which have become the new, all encompassing, food devils. Every conceivable human health problem has been attributed to the consumption of gluten, including fatigue (of course), obesity, diabetes, migraines, Alzheimer’s and, even, autism. (This last one has been pushed by, no surprise here, Jenny McCarthy).

The demonization of gluten, which is a protein found in grains like wheat, can be traced to bestselling books like Wheat Belly and the more recent Grain Brain. And the advocacy of hordes of gluten-free celebrities — including Gwyneth Paltrow and Steve Nash — has also played a big role. It has become a massive, multi-billion-dollar industry.

The popularity of gluten-free products is linked to the perception that the food is healthier and that adopting a gluten/wheat-free lifestyle will help people lose weight. Indeed, a survey of more than 200 dietitians pegged gluten-free as 2013’s most popular diet and weight-loss approach.

But what does the relevant science say?

Unfortunately, the evidence does not provide straightforward answers. Let’s start with the facts that seem pretty certain. Despite claims to the contrary, no credible study has shown that gluten/wheat is the cause of the current obesity epidemic.

There is also no credible evidence to suggest that going gluten-free is a wise lifestyle choice — unless, of course, you have a clinically identified reason for doing so (e.g., about 1 in 133 have celiac disease). Nor is it a proven weight-loss strategy. In fact, some studies have found that going gluten-free can lead to weight gain. A 2006 study, for example, followed 371 gluten-free dieters and found that 82 per cent gained weight after two years.

There are many anecdotal reports of gluten-free weight-loss success, often connected to some superslim celeb. For example, a 2013 article from the Daily Mail with the headline “Gluten-free devotee Miley Cyrus shows off her flat stomach” tells us that the “bread, pasta and pizza-free way of life seems to be paying off for Miley Cyrus.”

It is safe to say you can ignore this kind of hype. Anecdotes and personal testimonials — no matter how compelling and belly button revealing — are not good science. The evidence tells us that whole grains are, despite the popularity of this diet graze, good for you. They are, for example, full of fibre and vitamins. Studies have consistently found that the healthiest diets, such as the Mediterranean diet, contain whole grains and that they are associated with a range of health benefits, including a reduction of chronic diseases and a lower risk of cognitive impairment.

Indeed, it seems likely that much of the gluten-free craze is the result of celebrity culture and opportunistic marketing. Gluten-free products are generally much more expensive and, one can assume, more profitable.

OK, so going gluten-free isn’t a smart weight-loss or nutrition strategy, but what about the ever-increasing number of people who don’t have celiac disease but still report sensitivity to gluten? These are individuals who feel gluten is causing things like stomach pain, diarrhea, bloating and fatigue. This is where, admittedly, things get a bit confusing.

On the one hand, some researchers question the very existence of non-celiac gluten sensitivity. To cite just one example, a recent impressive study from Australia used a sophisticated double-blind approach (i.e., neither the researchers, nor the research participants knew whether the food was truly gluten-free) and found no evidence of gluten sensitivity. An editorial accompanying the study, which was published in the journal Gastroenterology, suggests the research “calls into question the very existence of NCGS (non-celiac gluten sensitivity) as a discrete entity.”

As a result of this kind of work, some in the medical community believe people feel better when they go gluten-free simply because they start eating a healthier diet, such as consuming more fruits and vegetables.

On the other hand, some studies suggest as many as 6 per cent of the population could have some degree of gluten sensitivity. (A more recent study from Columbia University put that incidence at a much lower 0.55 per cent.)

The bottom line: the science on gluten sensitivity is still emerging. An excellent review of the most recent research, published last month, put it this way: “Non-celiac gluten sensitivity is an entity awaiting validation, better diagnostic criteria, and, if it does exist, pathogenic mechanisms.”

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So, it turns out that Seth Rogen was right; gluten remains a pretty “vague term”. Still, I think the bulk of the science tells us that the vast majority of us do not need to hide from gluten. Gwyneth and Miley may believe gluten-free works wonders, but the science tells a different, more complex, story.