The salt levels in foods from popular fast food chains vary around the world, a new study finds, with food sold in Canada containing some of the highest levels of all.

The study, published in Canadian Medical Association Journal, looked at the salt content of food items in Canada, Australia, New Zealand, France, the United Kingdom and the United States from six fast food chains:

  • Kentucky Fried Chicken
  • McDonald's
  • Domino's Pizza
  • Pizza Hut
  • Burger King (known as Hungry Jack's in Australia)
  • Subway

The researchers looked at more than 2,000 burgers, chicken products, pizza, breakfast items, salads, sandwiches and french fries.

They found that fast food in Canada and the U.S. contained much higher levels of sodium than sold in the U.K. and France.

In Canada, McDonald's Chicken McNuggets, for example, contained 600 mg of sodium per 100 g serving, compared to 240 mg sodium in U.K. similar-sized servings -- nearly two-and-a-half times the amount.

Study author Dr. Norm Campbell, an expert in high blood pressure from the University of Calgary, says the results were surprising.

"In every food category, if we weren't first, we were second from the top in the amount of salt. If this was the Olympics of adding salt, we'd be in the gold or silver medals in every category," he told CTV News.

Campbell was also surprised to find Canada had some of the highest levels of sodium in our fast food salads.

"Most people think they are getting something healthy but they are not," he says.

Too much dietary salt has been linked to high blood pressure and other health problems. Campbell estimates that there are 7.5 million Canadians with high blood pressure, and about 2 million of them have hypertension because of too much salt in their diet.

Studies have shown that reducing salt intake could prevent a number of heart disease and stroke-related deaths.

"We estimate 14,000 die every year, and over 40,000 are hospitalized from strokes, heart attacks and kidney failure because of this issue," says Campbell.

Food companies often cite technical processing issues as the reason why they can't lower the sodium content in their products, stating that new technology and processes are needed to make lower-salt products. This study suggests that food makers in some countries have already found a way to make those changes.

"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 authors conclude.

The authors say that food makers often say the other reason they are reticent to lower the salt content in their foods is worries about consumer backlash. But they say that if sodium levels were reduced gradually, many consumers wouldn't notice.

"If reductions were made incrementally over several years, fairly large cumulative decreases in salt content could be achieved without consumers being aware of the changes in the products' formulations," they write.

The Canadian Restaurant and Foodservices Association says that the study being published today was in fact conducted two years ago and that much has changed since then.

"In the two years since the CMAJ study was conducted, restaurants have made significant progress in reducing sodium levels and introducing new, lower-sodium menu items, while still delivering the great-tasting, safe and high quality food that our customers expect. These efforts are ongoing," the group said in a statement provided to CTV News.

"Canada's restaurant industry is actively working with suppliers and health and nutrition experts to help Canadians reduce their sodium intake."

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip