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 fight­ 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 doc­torsnotes@thes­

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