These are the top sources of food poisoning, according to a chef-turned-microbiologist

These are the top sources of food poisoning, according to a chef-turned-microbiologist

TORONTO (CTV Network) — It’s easy to forget that when you dine out, you’re putting your night — maybe even your health — in someone else’s hands.

According to the Public Health Agency of Canada, four million Canadians get sick each year from contaminated food, and food-related illnesses result in more than 11,500 hospitalizations and 250 deaths annually. spoke with food safety experts about the food they approach with extra caution when dining out, and the list is longer than you might expect.


Keith Warriner is a food specialist with both the kitchen credentials and the academic rank to prove it.

Warriner trained and worked as a chef in the United Kingdom before completing his PhD, and in 2011, he became a professor of food science at the University of Guelph.

Warriner said one way to lower your risk of food poisoning when dining out is to avoid eating high-risk foods at high-risk restaurants.

“When you go into a restaurant, you look at the front of the house for a start and you say, ‘Does this look good?’ This is their best foot … their best showing,” he told in a phone interview. “What goes on in the kitchen will be worse than that.”

Before ordering a dish that carries a higher risk of food poisoning, Warriner said diners should check their local public health website for any red flags like failed health and safety inspections, assess the cleanliness of the restaurant and pay attention to how busy it is. When business is slow, he said, food tends to sit around longer, creating more opportunities for harmful food-borne pathogens to flourish.

“The way to look at food safety is this sort of time, temperature and obviously cleanliness,” he said. “If it’s an open kitchen, you can look inside and see what they’re doing.”

With those tips in mind, here is the food experts say you should only order from restaurants you really trust.


According to Health Canada, leafy greens can become contaminated with harmful pathogens such as E. coli and salmonella right in the fields where they grow.

The same thing can happen with the seeds harvested to grow sprouts, according to Michael Gaenzle, a scientist who teaches food microbiology and microbial food safety at the University of Alberta in Edmonton.

“The worst offenders are probably sprouts,” he told in a phone interview. “In sprouts, you amplify the risk because during germination, organisms have the opportunity to grow.”

Sprouts and leafy greens can also become contaminated during packing, processing and shipping. Because they are eaten raw, there’s no opportunity to kill those germs with heat.

Many of these factors are beyond the control of a restaurant, Warriner explained, but there are ways to minimize the risk of contamination in the kitchen.

“In the restaurant, there can be cross-contamination,” Warriner said. “(Like) cutting boards which you have meat on and then put the salad on.”

According to the U.S. Centers for Disease Control and Prevention, greens should be washed thoroughly, stored in a clean refrigerator with the temperature set to 4.4 C or colder and cut on clean cutting boards.


Gaenzle described eating medium-rare ground beef as akin to playing “a game of Russian roulette.”

“We know that approximately 0.5 to one per cent of the ground beef batches, even from federally inspected plants, are contaminated with Shiga toxin-producing E. coli,” he said. “That means your medium-rare hamburger then has a one-in-100 or a one-in-200 chance of making you ill.”

E. coli tends to live on the surface of a cut of beef and Warriner said those pathogens can be redistributed all throughout the meat during grinding. That’s why Health Canada states ground beef should be fully cooked to an internal temperature of 71 C, while steak can be served medium-rare, at a temperature of 63 C.

Chicken is another story.

According to Health Canada, poultry carries pathogens like salmonella and Campylobacter that can cause severe diarrhea, fever and abdominal cramps. To kill all the harmful bacteria that might be present on raw chicken, the meat should be cooked thoroughly.

For that reason, Warriner advised never to eat poultry that doesn’t seem fully cooked or arrives at the table feeling lukewarm.

“If you’ve got something that’s lukewarm, it’s either not been cooked or it’s being held at the wrong temperature,” he said, adding that it might be more common for kitchens to send out undercooked chicken than you think.

“If you’re in a high-pressure restaurant, they want to get the food out quick as they can. And often this means they don’t use a thermometer in the kitchen,” he said. “I must admit, when I used to work in kitchens … I don’t remember seeing them.”


Warriner never eats raw oysters — both as a matter of personal preference and due to the risk of norovirus and other gastrointestinal illnesses — and he only eats sushi from trusted, high-turnover restaurants that go through their supply quickly.

Part of the problem with seafood, he said, is that its high value means restaurants are loathe to throw it out when it starts to turn old. The longer raw fish sits around in a kitchen, the higher the likelihood of food poisoning.

“Some restaurants, they see food going into the bin as dollars going into the bin, and I’ve seen outrageous things happen in my time,” he said.

Gaenzle said mussels and oysters are especially risky compared to most fish because of the way they feed.

“Mussels are filter feeders,” he said, “which means whatever microbe or viruses in the water will be concentrated in the mussels.”


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Speaking of turnover, Warriner avoids buffet-style restaurants where the food isn’t being quickly eaten and replenished.

“If it’s not busy, then you can pretty much assess that the food’s going to be waiting there a long time, and they’re not going to throw anything out because that’s profit,” he said.

Warriner said the bain-marie warming counters most buffets use aren’t very efficient at keeping food warm, so the longer food sits on a buffet counter, the greater the opportunity for harmful pathogens to grow.

For the same reason, he pays attention to how staff replenish buffet items and chooses restaurants where the buffet containers are replaced completely once empty, rather than refilled or topped-up with more food.


Warriner said garlic infused oil can be a source of botulism, a rare but serious illness caused by a toxin that attacks the body’s nerves and causes difficulty breathing, muscle paralysis and even death. This toxin is produced by Clostridium botulinum and a few other Clostridium bacteria that thrive in anaerobic, or non-oxygenated, environments.

“We all know garlic is a source of botulism and oil gives the anaerobic environment so it can grow,” Warriner said.

Poorly stored or prepared mayonnaise can also harbour food-borne pathogens. Warriner said homemade mayo is especially risky, because home recipes often don’t call for enough acid — vinegar, in mayo’s case — to kill bacteria that might be present in the raw eggs used to make the condiment.

“Homemade mayonnaise is a disaster zone,” he said. “If they say, ‘We make our own mayonnaise,’ you think, ‘Oh geez,’ because they never put enough acid in, that’s the trouble.”

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