How you can protect yourself from food poisoning
There’s more to preventing sickness than just watching expiry dates. Even food that looks and tastes fine can carry harmful bacteria
Food poisoning is a problem, but it doesn’t always have to do with expiry dates.
According to Health Canada, approximately one in eight Canadians suffer from food poisoning each year. Fortunately, the vast majority of people recover quickly, but at least 10,000 are hospitalized and more than 200 people die as a result of something that they ate.
When people get very sick, it’s because they ate food contaminated with dangerous microbes (moulds, bacteria and viruses). These include norovirus, E. coli, salmonella, shigella and listeria. Our food safety network constantly tests for these microbes and food recalls are issued almost weekly by the Canadian Food Inspection Agency.
In my lab at the University of Toronto, we study E. coli and salmonella. When people find out what I do for a living, they ask what they can do to protect themselves.
I often get asked about expiration dates on food. These dates relate to food quality or freshness — not whether the food is safe to eat. The microbes that cause food to spoil, smell and taste bad aren’t typically the same kind that cause severe food poisoning.
That means two things. First, food that has passed its expiration date won’t necessarily get you sick if you eat it — although I don’t recommend making a habit of eating expired food. Second, fresh-looking food still can send you to the hospital because it carries very low numbers of dangerous microbes such as salmonella.
Many people don’t know most microbes don’t pose any threat to us. Our bodies are home to communities of microbes called the microbiome that keeps us healthy. About 500 species of microbes live harmlessly in all our intestines — including E. coli.
So, if E. coli is already in our digestive systems, why aren’t we sick all the time?
As it turns out, there are several varieties of E. coli. Some safely colonize the human intestine, don’t produce toxins and can’t invade our deeper tissues. Other types can be found in cows’ and pigs’ intestines. These types, like the dangerous O157: H7 strain, can cause severe disease in humans. Almost all strains of salmonella are dangerous.
So we aren’t concerned about every microbe out there — we only worry about those few, specific types that make toxins or have special tricks to avoid our immune defences.
Making matters worse, however, is that salmonella and toxin-producing E. coli often live in and among the animals on the farms that produce our meat and eggs. Even healthy-looking chickens, pigs and cows could still carry toxin-producing bacteria. Imagine the meat from those animals becomes slightly contaminated during processing. Then it’s loaded onto a refrigerated truck and number of bacteria are kept relatively low. The meat is transported to the supermarket, where someone slices it. A bit of the contaminated meat juice gets onto the knife, which the butcher then uses to cut some other meat. It also becomes contaminated.
If you bring any of that chicken or beef home and leave it out on your kitchen counter, a few little toxin-producing bacteria can divide into thousands, growing exponentially over just a few hours.
You won’t be able to see or smell these microbes, so you should always assume they’re there. Once meat is thawed, don’t let it reach room temperature — if that happens, you can be sure if there’s toxinproducing E. coli in there, it’s growing.
Now, with a large population of diseasecausing microbes on the surface of the food you’re about to cook and eat, there’s a potential you could become very sick — even though the meat still appears to be fresh.
When I cook, I like to thaw my meat on a plate in the fridge over 24 hours. This minimizes the amount of time it might have to spend out before it is cooked.
The final barrier to illness is cooking food properly, ensuring meat reaches a certain internal temperature — which varies depending on the kind and cut of meat — to make sure all the dangerous microbes are destroyed.
A clean kitchen also goes a long way to keeping you safe. All you need is soap and water to wash your countertops down after preparing food. The dish soaps sold today are very effective at destroying most of the microbes that might have come into contact with your kitchen surfaces. Even if a few microbes remain, without a source of food to keep them alive, most will dry out and die on an otherwise clean countertop.
A great source of simple food safety tips is provided by the Partnership for Food Safety Education at fightbac.org. But the bottom line is this: keep it cold, cook it thoroughly and ensure your kitchen is clean. William Navarre is an associate professor at U of T’s Faculty of Medicine’s Department of Molecular Genetics. Doctors’ Notes is a weekly column by members of the U of T Faculty of Medicine. Email email@example.com.