Emerging research suggests that sugar may be linked to deadly diseases, but Health Canada’s current food labelling regulations make it tough for Canadians to get an easy picture of how much of the sweet substance they are consuming — and it doesn’t look like that’s going to change any time soon.

The groundbreaking and controversial research explored by the CBC’s the fifth estate in its season premiere tonight links sugar to diseases ranging from diabetes to cancer and Alzheimer’s.

“Sugar is toxic beyond its calories,” Dr. Robert Lustig, an expert on childhood obesity at the University of California, San Francisco, told the fifth estate’s Gillian Findlay.

Watch The Secrets of Sugar on the fifth estate on CBC-TV tonight at 9 p.m.

While Canadians have become used to warnings about the dangers of consuming too much fat or salt, nutrition labels on food have never included recommended daily limits specifically for sugar.

Health Canada does not have a recommended limit for how much sugar Canadians should consume in a day.

A representative of Food and Consumer Products of Canada, an industry organization that represents the largest food companies in the country, says it sees “no need” for a recommended daily limit on sugar intake.

Health Canada declined numerous requests by the fifth estate for an interview, but former Health Canada employees did speak off the record, and said the department does not think that sugar should be singled out as a major culprit behind chronic diseases.

Stirring up debate

According to Statistics Canada, the average Canadian consumes 26 teaspoons of sugar per day. That works out to 40 kilograms per year —– or 20 bags.

While neither the Canadian nor U.S. governments has a recommended daily limit for sugar consumption, one major U.S. medical group is recommending people cut back on the sweet substance.

The American Heart Association is suggesting men consume no more than nine teaspoons a day. For women, the recommendation is a maximum of six teaspoons.

Dr. Robert Lustig, as expert on childhood obesity at the University of California, San Francisco, says 'sugar is toxic beyond its calories.' (CBC)

That recommendation comes as research from a small but influential group of medical researchers is stirring up debate on the impact sugar has on health.

One of the most vocal of those researchers is Lustig, an author who has become a YouTube sensation for a 90-minute lecture in which he calls sugar a toxic poison.

“I use those words and I mean them. This is not hyperbole. This is the real deal,” he told Findlay.

“Everyone thinks that the bad effects of sugar are because sugar has empty calories. What I’m saying is no, there are a lot of things that do have empty calories that are not necessarily poisonous.”

Breaking down the sugar

Lustig says that sugar, which is made up of glucose and fructose molecules, is a poison because of the way our bodies break it down.

“When you metabolize fructose in excess, your liver has no choice but to turn that energy into liver fat and that liver fat causes all of the downstream metabolic diseases.”

But not everyone agrees with Lustig’s theory, including other doctors and food industry representatives.

Dr. John Sievenpiper, a researcher at St. Michael’s Hospital in Toronto, questions Lustig’s methodology and his view that "sugar and only sugar" is the prime factor in the international food supply that “predicts [the] diabetes rate worldwide."

Sievenpiper notes that during the same time period when Lustig points to increasing sugar consumption and rising rates of obesity —– something that has been linked to diabetes — there was also increasing consumption of bottled water.

We have to be careful in putting too much of the biological plausibility in wanting to believe patterns that we see. - Dr. John Sievenpiper

“But there's no real biological plausibility in the link between bottled water and [being] overweight and obesity. We have to be careful in putting too much of the biological plausibility in wanting to believe patterns that we see.”

Sievenpiper isn’t recommending people eat a lot of sugar, but he does suggest we should be careful about saying fructose is largely responsible for various health problems.

“As long as you match for calories, fructose does not behave differently than does any other form of carbohydrate, namely starches or fine starches and glucose. And that's not to say that they're benign, because I don't think we should be having a lot of refined starch or glucose. But it's not behaving any differently.”

Industry skepticism

A representative of Canada’s largest food industry association is also skeptical of Lustig’s research.

Phyllis Tanaka, vice-president of scientific and regulatory affairs for Food and Consumer Products of Canada, isn’t worried about Lustig’s claims about one of her industry’s key ingredients and doesn’t think consumers should be either.

Phyllis Tanaka, vice-president of scientific and regulatory affairs for Food and Consumer Products of Canada, says her group has worked with Health Canada over the last few years on how to help consumers make 'informed choices.' (CBC)

“I think it’s important that we step back and look for ways to educate and help consumers fit sugar into a healthy dietary pattern,” she said.

But current food labelling regulation can make it difficult for consumers who want to avoid sugar.

On Canadian nutrition labels, manufacturers are required to list ingredients in order from greatest to least volume. But many labels list multiple kinds of sweeteners with different names. For example, honey, barley malt syrup and evaporated cane juice could all be listed separately, even though the human body treats them all as sugar.

Also, sugar is measured in grams on labels, instead of more consumer-friendly teaspoons. For someone trying to keep track of intake, four grams of sugar equals one teaspoon.

In a can of Coke, for example, there are more than 10 teaspoons of sugar. The popular “Healthy Choice” microwave chicken dinner has 5½ teaspoons.

Tanaka says her group has worked with Health Canada over the last few years on how to help consumers make “informed choices,” and that for those who want to avoid sugar, all the information they need is already on the label.

“At this point in time, I’m comfortable in saying the science just isn’t there to support a role in chronic disease.”

Watch The Secrets of Sugar on the fifth estate on CBC-TV tonight at 9 p.m.