For the average adult, that would be about six teaspoons (30 millilitres) of sugar a day — less than the sugar contained in a single can of sugar-sweetened soda. For children, it could be as low as three teaspoons (15 ml) of sugar a day, said Dr. Francesco Branca, director of the WHO's department of nutrition for health and development.
In draft recommendations issued Wednesday, the Geneva-based global health agency reaffirmed the advisability of limiting one's intake of sugar to no more than 10 per cent of one's daily calorie intake. But it said if people could get to five per cent, that would be better.
"The five per cent would probably be the ideal one and the 10 per cent is the more realistic one," Branca said in a teleconference for journalists.
Both would likely be a stretch for many Canadians. And experts acknowledged it would likely take a seismic shift in food formulation and consumption patterns in a country like Canada for most people to be able to reach the five per cent target.
The goal would be unreachable for people who eat out or rely on prepared or processed foods as a regular part of their diets, said Dr. Yoni Freedhoff, an Ottawa-based obesity expert.
"Five's a really small number. The likelihood of anybody getting down to five in this environment without cooking everything entirely from scratch is very, very low," he said.
"That doesn't mean it's a bad thing to give the suggestion that we should be aiming low. It just means that the likelihood of anybody getting there is not particularly high."
That's because sugars are added to many foods, everything from breakfast cereals to fruit and energy drinks, sauces, baked goods and condiments. A tablespoon (15 ml) of ketchup, for instance, contains about one teaspoon (five ml) of sugar.
In addition to being ubiquitous, free sugars have many names — molasses, sucrose, fructose, anhydrous dextrose, malt syrup and honey, to name just some. Some labels might list "raisin puree" or added juices. So spotting exactly how much added sugar prepared foods contain is no easy thing.
Statistics Canada does not have data that teases out what proportion of Canadians' calorie intake comes from free sugars versus intrinsic sugars.
Free sugars are sugars added to foods by manufacturers, cooks or the people eating the food — brown sugar sprinkled on oatmeal, for example — as well as natural sugars found in fruit juices, honey, syrups and molasses. Intrinsic sugars are the sugars in whole foods like fruit.
Intrinsic sugars are not included in the WHO intake limit recommendations; these are sugars locked into whole foods, such as a piece of fruit. So the sugar in an orange is intrinsic. The sugar in orange juice — even freshly squeezed in your kitchen — is free sugar.
The most recent Canadian data, from the 2004 Canadian Consumer Health Survey, shows that on average Canadians consumed 110 grams of sugar a day that year — the equivalent of 26 teaspoons (130 ml) of sugar. Sugar calories made up 21.4 per cent of the average Canadian's total calorie intake.
Didier Garriguet, a senior analyst with Statistics Canada, said because of the way the data were collected, there is no way to tease out the free sugar intake from the total sugar intake. Garriguet said another nutritional survey is planned for 2015 and he hopes it will provide a clearer picture of the breakdown of sugars in Canadians' diets. But others say without better food labelling in Canada it will remain hard to generate those breakdowns.
The WHO draft recommendations differ from earlier iterations in setting the target of less than five per cent. The less than 10 per cent recommendation was first issued by the WHO in 1989. The draft recommendations will be open for public comment for the rest of March, after which the WHO and scientific advisers will finalize the guidance.
The recommendations are likely to be contentious. And nutrition experts who have been waiting for the recommendations expect pushback from the food industry, which would need to dramatically reformulate products if consumers were to be able to meet the targets and still eat prepared and packaged foods.
In 2004 when the WHO tried to include the 10 per cent sugar limit recommendation in its Global Strategy for Diet, Physical Activity and Health, the U.S. Congress — under pressure from the sugar industry lobby — threatened to withdraw U.S. funding for the agency. The direct reference to the 10 per cent figure was removed from the final report.
Branca said he doesn't anticipate the same degree of opposition this time.
And Mary L'Abbe, chairwoman of the department of nutritional sciences at the University of Toronto, said she believes the fact that there is growing attention to this issue will make it harder for industry to object this time.
L'Abbe, who was on a scientific group that advised the WHO on the recommendations, likened the situation to when the tide started to turn on trans fats. As attention to the health risks associated with consumption of trans fats grew, consumers started to express concern and manufacturers scrambled to rework the recipes of their products.
That would be useful for sugars as well, but Branca said it won't be enough. "Reformulation of products will not reduce the amount of sugar intake to the level required. So that needs to be compounded with a genuine change in behaviour."
L'Abbe suggested Canada should piggyback off the proposed new labelling requirements in the United States, which will mandate that food manufacturers will need to show total sugars in a product. Multinational food producers will be doing this for the U.S. market, so doing it for the Canadian market as well won't be much additional work, she said.
Freedhoff suggested taxes may need to be raised on high-sugar products like sugar-sweetened soft drinks.
"It's not just about personal responsibility," he said. "I think the government absolutely has a role to play in this as well."
The recommendations look at limiting sugar intake in relation to lowering the risk of obesity and tooth decay, two conditions scientific studies suggest are linked to excess sugar consumption.
The report said consideration was also given to looking at the evidence related to sugar intake and two other conditions — heart disease and diabetes. But in the end the focus remained on obesity and tooth decay.
In Canada, the Heart and Stroke Foundation began a consultation process this week to determine if it should recommend that Canadians restrict the portion of their daily calories that come from sugar.
It is considering following the lead of the American Heart Association, which suggests that added sugars make up no more than half of one's daily discretionary caloric allowance, which it says would be no more than 100 calories or six teaspoons (30 ml) a day for most American women and 150 calories a day or about nine teaspoons (45 ml) of sugar for men.
Follow @HelenBranswell on Twitter.
Also on HuffPost