Salt levels in meals sold at major fast food chains vary substantially across developed countries, according to a new study that challenges the industry and governments to get tougher to protect public health.

Too much salt fuels high blood pressure.

But reducing the amount of sodium in the diet to recommended levels could prevent premature deaths from heart disease and strokes, saving 11,000 to 15,000 lives of Canadians a year, experts estimate.

In Monday's issue of the Canadian Medical Association Journal, an international team of researchers compared the salt content of 2,124 items from six fast food establishments:

  • Burger King.
  • Domino's Pizza.
  • Kentucky Fried Chicken.
  • McDonald's.
  • Pizza Hut.
  • Subway.

The average salt content varied between companies and between the same products sold in different countries.

Calgary-based Dr. Norm Campbell of the Canadian Stroke Network and his co-authors pointed to McDonald's Chicken McNuggets. The snacks contained 0.6 grams of salt per 100 grams in the U.K. — where the fast food industry actively participated in slashing salt. But McNuggets in Canada contain 1.5 grams compared with 1.6 grams in the U.S. for the same 100-gram size.

Canadian salads topped the list with 0.8 grams of salt per 100 grams.

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Most consumed sodium comes from common restaurant or grocery store items that vary in salt content in different countries. (Amy Sancetta/Associated Press)

"Decreasing salt in fast foods would appear to be technically feasible and is likely to produce important gains in population health — the mean salt levels of fast foods are high, and these foods are eaten often," the study's authors concluded.

"Governments setting and enforcing salt targets for industry would provide a level playing field, and no company could gain a commercial advantage by using high levels of salt."

Industry volunteer efforts not working, doctor says

After the Sodium Working Group said Canadians should consume only half the sodium they're now taking in from foods and drinks in 2010, the food industry agreed to lower targets.

Early last year, the federal government disbanded the working group that was supposed to oversee the food industry's plans to cut back on salt in processed foods and items in restaurants.

In January, health groups wrote to Ottawa to complain about the lack of progress.

The industry's voluntary efforts aren't working, Campbell said in calling for oversight of the 2016 targets and timelines as well as stronger regulatory measures if needed.

"The federal government is focusing its efforts on reducing sodium through public awareness and education activities to assist individuals so they can make informed food choices, guidance to the food industry about ways to reduce sodium in processed foods, and research to learn more about sodium and health," Health Canada said in an email.

"The federal, provincial and territorial governments are committed to helping create conditions that make the healthier choice the easier choice."

Large serving sizes

Ottawa said it has worked with the food industry to reduce sodium in processed foods through regulatory changes, such as allowing alternative ingredients or food additives to sodium like sorbic acid in processed cheese.

"We support a flexible approach that supports industry to meet the 2016 sodium reduction goal," Health Canada said. "This is an especially important consideration given the current fragile economic recovery."

An average Canadian adult can safely eat less than one teaspoon of salt a day, which means two slices of frozen pizza is overdoing it, said registered dietitian Rosie Schwartz, of Toronto.

Our palates need to change over time, Schwartz said.

"Health Canada is really working together with industry," Schwartz said. "They say to lower the sodium in foods when they should really be looking at the health of Canadians first and looking at the health of industry second."

Manufacturers respond

The Canadian Restaurant and Foodservices Association has said salt needs to be reduced gradually from processed foods to avoid turning off consumers, who also need to be educated.

"If they did the research today, they'd find there'd been further reductions on sodium content," said Garth Whyte, president and CEO of the association.

"Depending on the product you pick, we're leading or we're lagging."

While Canadians already have some of the lowest sodium levels in the world, manufacturers are committed to reducing it more, says the Food & Consumer Products of Canada. The trade group represents processed food makers including Campbell, Heinz, Kellogg Canada and Clover Leaf Seafood.

In the study, researchers used company websites to analyze salt levels in:

  • Savoury breakfast items like hash browns and sandwiches.
  • Burgers.
  • Chicken products.
  • Pizza.
  • Salads.
  • Sandwiches.
  • French fries.

Salt levels varied more per serving than per 100 grams, particularly for french fries, the study's authors noted.

"What they found was great variation, and that seems to prove that it is possible in some cases to reduce the salt in food," said CBC medical specialist Dr. Karl Kabasele.

Large serving sizes for burgers and chicken products had more than six grams of salt per serving, and the saltiest sandwiches contained eight grams.

The average salt level in sandwiches was 70 per cent higher for Pizza Hut than for Subway, the researchers said.

The study's authors acknowledged they relied on the veracity of data from the companies' websites.

The researchers spot-checked the accuracy of their data by testing a random sample of five per cent of the entries against the original internet source.

Campbell reported receiving travel expenses from Boerhinger Ingelheim, which makes anti-hypertension drugs.

With files from CBC's Pauline Dakin