Critics say the anti-wheat claims made by leading health crusader Dr. William Davis are based on shaky science, an investigation by the fifth estate has found.

Davis is the author of the No. 1 New York Times best-selling book Wheat Belly, considered the bible of the wheat-free movement. He argues wheat has killed more people than all wars combined, and that it is responsible for an astonishing array of diseases — diabetes, obesity, Crohn’s disease and autoimmune disease, among many others.

He also claims the wheat we eat now is not what it used to be. Rather, it’s a genetically modified monster he calls "Frankenwheat" — and he says it’s killing us.

In the fifth estate’s War on Wheat, Davis tells Mark Kelley, "I’m waging a war against misinformation in health, in which one of the major and most destructive messages is to create a diet rich in healthy whole grains."

Davis is an unlikely warrior. He was a cardiologist in Milwaukee, trying to lose a few pounds to help fight his type 2 diabetes. He never conducted any of his own scientific studies, but found that after cutting wheat from his diet, his blood sugar levels were significantly reduced and his extra weight melted away.

He also heard similar stories from others: “Patient after patient came back and said, 'Well, I did that, my blood sugar’s much better and I also lost 43 pounds and I didn’t do anything else.'"

Davis and others in the anti-wheat movement are changing the way people eat — 56 per cent of Canadians now report they’re cutting down on foods such as bread, breakfast cereals, pastas and pastries. Gluten-free and wheat-free products are filling store shelves, with more than $6 billion in sales last year.

Kellogg’s, the world’s largest cereal maker, has seen its biggest drop in sales since the 1970s. Food companies are selling off their struggling bread divisions, while wheat sales are plummeting across Canada.

That’s because millions of people are going wheat-free, influenced by best-selling health evangelists and celebrities who say wheat is responsible for everything from fat bellies to breast cancer to schizophrenia.

About one per cent of the population does get sick from eating wheat – people with celiac disease. Still others have allergies and sensitivities to wheat. But Davis insists wheat is dangerous for everyone, causing high blood pressure, heart diseases, dementia and cancer.

Anti-wheat claims questionable at best: critics

But the fifth estate’s investigation found that experts in the scientific community say scientific claims made by the anti-wheat movement are questionable at best.

Joe Schwarcz, a chemist at McGill University dedicated to demystifying science and debunking big claims, says, "This is one of these arguments that has one smidgen of scientific fact to it, which is then exploded into a whole blob of nonsense."

Schwarcz says he hasn’t seen any evidence that wheat has addictive properties, as Davis claims in his book. Schwarcz also says "opioid peptides" are produced when some foods are digested. But just because they can bind to opiate receptors in the brain doesn’t mean they produce a morphine-like effect.

"If we’re going to say that wheat is addictive," Schwarcz explains, "it’s along the line that people like foods that have wheat in them. It’s not a physical addiction."

It appears that Davis based this claim mainly on one study of rat brains, done on dead rats in 1979. The fifth estate could not locate any study on humans that conclusively proves wheat is addictive.

Davis also links wheat to mental illness such as schizophrenia. But the study he based his research on was conducted in 1966, and after almost 50 years of research, no one consulted by the fifth estate could point to any definitive study that specifically links wheat to schizophrenia.

What about Davis’s claim that today’s wheat is not wheat at all, but a "modern creation of genetics research"?

Researchers at the University of Saskatchewan have been studying the genetic profiles of 37 varieties of wheat grown in Canada since the 1800s, to discover if wheat’s basic protein structure has been altered in any way.

Sask. study finds basic structure of wheat unchanged

Wheat geneticist Dr. Ravi Chabbar is heading up the Saskatchewan project and is paid to advise the grain industry, but this particular project is being funded by the federal government.

Dr. Chabbar says that over time, wheat has been modified to produce high-yield crops. But when it comes to wheat’s proteins – gluten and gliadins – the basic structure of "ancient" and modern wheat is the same.

The Canadian Celiac Association, the American Heart Association, the Obesity Society and the American College of Cardiology all refuse to endorse gluten-free diets for anyone who does not have celiac disease.

But the fact remains that despite the vast majority of scientists and health organizations not supporting much of what Dr. Davis says, more and more people are giving up grains. There is continuous debate – in the media and around the dinner table – about who should be winning the war on wheat.

Yoni Freedhoff, a family doctor and diet expert who runs a nutrition clinic in Ottawa, says the eating guidelines touted in Wheat Belly are similar to other carb-free diets that get results by dramatically reducing the carbohydrates and calories people eat.

He argues that the difference here is Davis, not any miracle cure: "This just took it to another level with a very charismatic doctor, who has a presentation that to me is reminiscent of an evangelical preacher. You know, with ‘You can be healed,’ and away you go. And I think…it’s what people want to hear. We want to believe in magic."

Watch The War on Wheat Friday at 9 p.m. (9:30 NT) on CBC’s the fifth estate