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Ask a nutrition scientist: Food poisoning- when you should leave the leftovers alone

Sorry if this editorial is not very funny...but food poisoning is just nothing I can joke about.

Foodborne illnesses can be caused by bacteria, fungi, viruses and parasites, but also by toxins inherent of the consumed food. The last part would include mushrooms, fugu, or raw soybeans, and I will not cover this here. I also will not talk about parasites, but if you want me to cover them as well, write it in the comments. Usually, food can get contaminated by improper handling and storage of the food item.



Nausea, emesis (fancy name for vomiting), the runs, the belly gargling, pains, bleeding, dizziness, neurological disorders up to death, all of this can be caused by contaminated food. The symptoms vary depending on the dosage, the culprit, and sometimes your own health.
The worst thing is that the incubation period (time between eating and the problems) can range between hours to months (listeriosis), and often is not attributed to the stuff you actually ate.

Food infection vs food poisoning

food infections is when you ate a shitload of food with living bacteria, which now grow inside your gut, blood, cells.


Food poisoning is when you get sick from the toxin in the food produced by bacteria (the bugs are dead, but the toxin is, well, toxic) or when you ate live bugs, which now grow in your gut, and produce their toxins there.


Usually, bacteria are everywhere. No, really, even after you bleached your house, the cat and your kids. But they hang around only in small numbers. But when they grow, they copy themselves. One grows into two, into 4, into 8, 16, 32, and so on, and in minutes. They grow exponentially. And then they are a problem.

The common culprits:

There are dozens of bacteria that can cause trouble with food. However, the main culprits are campylobacter jejuni, clostridium perfringens, salmonella, and e.coli O157:H7 (EHEC), and lately, Listeria monocytogenes.


The bugs love certain types of food. These high risk foods are raw meat, poultry, mayonnaise, sea food, gravy, small goods, dairy, cooked rice and pasta, fruit salads and eggs. They love those things because sometimes, the bugs are present in huge amounts to begin with; others can be easily contaminated because of processing, and in some of the foods, the conditions to grow are just perfect for the bugs.

What do the bugs like?

Water: they need water, and they hate everything that reduces the water in the food they love. Tons of sugar or drying and salt make a good preservative; see pickling, brining, and jams.
Temperatures: every bacterium has its own happy zone when it comes to temperatures. The happy zone ranges between 5 and 60 C.
pH: bugs usually love neutral pH, but some love an acidic pH, like vinegar. Nobody really likes alkaline, it tastes like soap, see baking soda.
Time: bugs double every 15 minutes at their happy range. Raw meat out of the fridge overnight? …16,000,000 bugs, from one. Eww.
Oxygen: not all bugs need oxygen; some can grow happily without, like clostridium botulinum.


To sum this up:

The bugs (or their toxins) need to be present in the food, the food must be suitable for them to grow, the conditions must be right, like pH, water, and warmth, they must have time to grow, there must be enough numbers and toxin to make you sick, and you have to eat it…then you will get sick.


The common reasons for contamination:

Food left at room temperature, unwashed hands, cross-contamination (same utensil for fruit salad and raw poultry, for example), infected food handlers (sick person prepares fresh food), unclean utensils (change your washcloth regularly, peeps!), inadequate cooling temperatures, inadequate cooking or re-heating, slow cooling, inadequate hot holding temperatures (cafeterias), and contaminated raw foods and ingredients.

Contamination from veggies are on the rise, too. Especially from lettuce, spinach, sprouts, herbs.

How to prevent food poisoning

  • Wash all veggies with fresh drinking water before preparation
  • Separate all raw and high risk cooked and ready to eat foods at all times
  • Change utensils after you worked with high risk stuff, like fresh meat
  • Keep food covered, prevent insects and animals to get to food (no dogs in the fridge)
  • Wash your hands when handling food, do not cough or sneeze into your food
  • Wash your utensils really well immediately after handling raw meat
  • If you find spoilt food in the fridge, remove it immediately
  • Keep food out of the happy zone for bacteria growth (hotter than 60 C, colder than 4 C)
  • Do not leave high risk food at RT
  • Do not keep prepared food in the fridge too long; the cold does just slow down bacteria growth, it does not kill them

Use your senses: does it smell sour/off? Did it change color? Is the texture different? (slimy, pulling fine hairs when moved) Do not do a taste test!

If in doubt, throw it out!

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