You know the symptoms well enough. The clammy chill that washes over your body, the clenching in your stomach and then, finally, the dash to the bathroom, possibly accompanied by a split-second decision about which part of your body to aim at the toilet first.
But what’s happening inside your body when you have food poisoning?
Research published today has given us a slightly clearer idea, at least for one type of bacteria.
A team from the Australian National University looked at the way the body responds to the bacteria Bacillus cereus, which can cause food poisoning and sometimes lead to serious infections elsewhere in the body, including sepsis, pneumonia and meningitis.
They found a toxin secreted by the bacteria binds directly to cells in the human body and punches holes in the cells to kill them, triggering an immune response.
Understanding the way toxins produced by this bacteria provoke inflammation in the body is a key to understanding how to treat it, said lead researcher Anukriti Mathur.
“In certain cases where you’ve got a bacterial infection it would be really essential to boost our immune system so that it is stronger.
“However in cases such as sepsis, where you’ve got unwanted inflammation happening in your body, you want to dampen the inflammatory responses.
“A very unique balance is required in protecting us against different kinds of infections.”
But what is it about this bacteria punching holes in your cells that leaves you hunched over a toilet bowl?
It has to do with the parts of your nervous system being targeted by the toxins produced by the bacteria, according to Vincent Ho, a University of Western Sydney gastroenterologist and researcher who was not involved in the study.
Bacillus cereus produces more than 12 different toxins. One triggers vomiting and another diarrhea, Dr Ho explained.
The vomit-inducing toxin, called cereulide, binds to serotonin receptors in the stomach and small bowel and stimulates the vagus nerve, which controls muscle movement in the gut.
“That signals back up to the vomiting centres of the brain,” he said.
“And in a very similar way that is how the diarrheal form also works too. It’s causing direct stimulation of the small bowel, and that’s triggering a reactive response of reflex mechanism called the gastro-colic reflex.
“The toxins are stimulating against receptors in the gut lining … triggering a lot more movement of the muscle in the gut and the colon.”
Bacillus cereus can be found in vegetables, rice and pasta, as well as meat and fish, and will grow in these foods if they are stored at the wrong temperature.
‘Tis the season to be food-safe
While Ms Mathur’s study looked at just one of the toxins produced by Bacillus cereus, there are plenty more ways that bacteria in your food can make you sick.
Other microorganisms can cause you gut grief, including salmonella, campylobacter, listeria and Staphylococcus aureus, among others.
One thing all these nasties have in common is that they thrive in foods left at room temperature for too long — and summer brings increased risk.
Warmer weather and Christmas entertaining conspire to make food poisoning cases increase over the summer, said Lydia Buchtmann from Food Safety Information Australia.
Dr Ho explained bacteria tends to multiply most quickly at temperatures between 32 and 43 degrees Celsius — in other words, a hot Australian summer’s day.
“If you have 100 bacteria on a bit of food — which is hardly anything — at 8:00am, and it can double, let’s say, every 20 minutes, at 2:00pm you’ll have more than 26 million bacteria on the piece of food,” he said.
This is important because food poisoning tends to be dose dependent. That is, the more bacteria you ingest, the more likely you are to get sick.
Ms Buchtmann said other factors were at play when it came to food poisoning at this time of year.
“You also get more cases over the summer because you’re entertaining more, so you’re cooking for larger numbers of people, you’re putting the fridge under stress, overloading it, and you’re cooking for several generations of people.
“Some people have much more risk of food poisoning: the elderly, little kids, pregnant women.”
She urged people not to be complacent about food safety over the festive season.
“If you’ve got leftovers, as soon as they’ve stopped steaming, divide them into small portions in small containers so they cool really quickly and put them straight in the fridge or straight in the freezer.
“Use the leftovers in the fridge within two to three days. And if you’re at risk of listeria — so pregnant, elderly, immunocompromised — then you need to use leftovers within a day.”