TORONTO - A hamburger or stir fry from a chain restaurant may contain the total daily recommended amount of sodium Canadians should consume, suggests a study published Wednesday in the Canadian Journal of Public Health.

When it came to stir fries, some sandwich wraps and even salads, researchers were surprised at the wide variation in the amount of sodium they contained, said Mary L'Abbe, chair of the University of Toronto's department of nutritional sciences and senior author on the study.

"Some of the top quarter of the foods were above the upper level for a day, but yet the lower end were ... half your recommendation, so there was this big variety."

The daily recommended amount of sodium is 1,500 milligrams and no more than 2,300 milligrams — the equivalent of about a teaspoon of salt — is suggested per day. Research shows the average Canadian consumes 3,400 milligrams per day.

"You would normally think salad is a very healthy choice and so absolutely a large number of those salads were quite low in sodium ... but at the same time there were also salads that had up to 2,200 milligrams (of sodium) per serving," L'Abbe said.

"So you could get the low end and have only 200 milligrams of sodium and you could get the high end, 2,000 milligrams of sodium."

The University of Toronto study of 4,044 foods from 85 chain restaurants found that, on average, a single menu item from a sit-down restaurant, such as a hamburger, sandwich or stir fry, contained almost 100 per cent of the daily recommended amount of sodium, or an average of 1,455 milligrams of sodium per serving.

Side dishes contained almost half that, an average of 736 milligrams of sodium.

Many foods geared toward children were also found to be high in sodium.

Health Canada has been educating Canadians on reducing sodium levels, but the focus has been on packaged foods and the agency has not issued guidelines for the restaurant sector, L'Abbe said.

It's been estimated that reducing Canadians' dietary sodium intake by 1,800 milligrams per day would result in an annual health-care savings of $2.33 billion, L'Abbe and co-author Mary Scourboutakos, who worked on the study as part of her doctoral research, said in the report.

About a quarter of Canadians eat something prepared at a sit-down restaurant, cafeteria or other food venue every day. Too much sodium causes high blood pressure, a leading cause of illness and premature death, the Ontario Medical Association said in a statement.

"We're especially concerned because the sodium in restaurant foods is hidden," said Dr. Doug Weir, president of the Ontario Medical Association.

"There is no easy way for patrons to choose lower-sodium options, because for the most part sodium content is not posted on the menu. Our patients, and especially those at risk for high blood pressure (40 per cent of population), need better information so that they can choose lower-sodium foods in restaurants. Menu labelling is the best way to do this."

Dietitians of Canada, which helped prepare the Sodium Reduction Strategy for Health Canada in 2010, also says the food industry needs to cut down on added sodium.

"Sodium reduction targets need to be set, monitored and reported on foods available in the food supply and that includes foods in restaurants and other food service establishments," Janice Macdonald, the organization's director of communications, wrote in an email.

Sodium is a component of table salt, the chemical sodium chloride. It's used in many foods and not only for taste.

In bread, you need salt as part of the leavening process. It's often used to help foods brown. Sodium is used in processed cured meats as a preservative.

In the restaurant industry foods with salt and a variety of salt additives hold more moisture. When the food is being cooked ahead of time, it doesn't dry out, L'Abbe explained.

Ditching the salt shaker is only one way to decrease sodium consumption.

At a fast-food or sit-down restaurant ask if there are lower-sodium choices. When it's possible to customize your food, ask if they would not add salt to your food.

Choose lettuce, onions and tomatoes for your burger rather than cheese, ketchup, mustard and relish, which add more sodium. Order smaller portions and share. Ask for gravy, sauces and dressings on the side and use a lesser amount. Add flavour with herbs, pepper and other seasonings rather than salt, L'Abbe suggested.

Visit the Healthy Canadians website for more tips on choosing foods that lack sodium when eating out and grocery shopping.

Bill C-460, being debated in Parliament, is asking chain restaurants to provide calorie numbers and high-sodium warnings on menus.

Sodium Awareness Week kicks off March 11.

Also on HuffPost:

These are the six worst salty foods:
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  • 1. Bread And Rolls

    This tops the list because we Americans simply consume too much bread, period. A 1-ounce slice has 100 to 200 mg of sodium. Limit your intake to the size of a disk (100-percent whole grain, only of course -- you want to avoid those wrinkles, or at least enjoy better orgasms).

  • 2. Cold Cuts And Cured Meats

    Skip these altogether. The preservatives add a criminal amount of sodium to your meal. If you must do meat, lean ham and lean pork (tenderloin) will have less salt. Drop the Canadian bacon!

  • 3. Pizza

    It’s the perfect storm: bread, cheese, pepperoni and marinara sauce. One slice alone can make up more than half of your daily recommended intake! Go homemade with no-salt-added sauce, 100% whole wheat or other-grain-you-love dough, low-sodium cheese and leave the pepperoni at the door with the delivery.

  • 4. Poultry

    Go skinless, lean and grilled. Watch out for grilled chicken sandwiches at popular fast food restaurants, those have 820 - 1330mg of sodium! That’s almost your day right there.

  • 5. Soup

    Make your own rather than canned (those ”low-cal” soups have around 800 mg)! Choose a low-sodium broth and season with spices and herbs. There are some soups you <em>can</em> enjoy (see our <a href="">"You: On A Diet"</a> for several really great ones with less -- some way less -- than 480 mg of sodium per serving) For the main attraction, try dried beans and fresh vegetables.

  • 6. Sandwhiches

    Use the same meat alternatives as you do soup. Don’t forget about tofu and seitan! As for PB & J, try natural nut butters without added salt. To avoid going overboard on bread: open-faced sandwiches or fresh lettuce wraps.

  • Sodium And Your Body