A biological explanation of food poisoning please

June 25, 2012 1:10 PM

What is happening in the body when food poisoning occurs? Are the symptoms defensive actions or purely symptomatic?

My girlfriend—her of the iron stomach—ate dinner with my parents and I the other night. First up: scallops, fried. Second: salmon steaks, fried, with various sundries. Cake and cheeseboard followed. Two glasses of wine.

Two hours later, after a walk to the beach and back, she throws up everything. In the forty-five minutes preceding she feels very queasy. After vomiting she still feels a little bad, but generally much better. We go to sleep. The next day she's mildly tired but otherwise fine.

We put it down to a bad scallop, since everyone else was unaffected. It got us talking about food poisoning. What exactly is going on? Is the vomiting a symptom forced upon the body by bacteria or, as it very much appears, something the body enacts to eject the bad stuff? Similar with diarrhea. Do the symptoms depend on the type of bacteria ingested? Are these symptoms actually defences to prevent things going any further, or are they negative consequences? Does the delay between eating and feeling sick depends on bacteria multiplying? How does the body detect a problem, if these are defensive manoeuvres?

Why is seafood so susceptible to bacteria that can sicken us? Or are most shellfish poisonings, as hinted at by the wikipedia page, a toxin poisoning?

I've read the wikipedia page, but it doesn't really explain how the symptoms come about or what is happening in the body. I realise there are a lot of questions above. I don't mind in-depth explanations or links. Thanks.

posted by distorte to science & nature (13 answers total)

It's soooooooo broad what could have caused her issue. Typical food poisoning actually takes more than a day to usually set in so it may not have actually been what she ate for dinner.
posted by ZaneJ. at 1:25 PM on June 25, 2012 [1 favorite]

Does she often eat much, or eat rich foods? That dinner might have caused me some distress, with the fried things and the cheese and cake all together. It may not have been the scallops at all.
posted by fiercecupcake at 1:28 PM on June 25, 2012

Food poisoning can come from a number of sources, and the body's reaction basically depends on the source. Poisoning can be viral (causing disease in the victim), chemical (foreign contaminants in the food), or something else. Food poisoning from Staph isn't caused by the bacteria itself, it's caused by the toxins produced by the bacteria hanging out on lukewarm food for a long time, and symptoms can present in 1-4 hours. Norovirus, far more common than Staph, takes 24-48 hours to develop.
posted by LionIndex at 1:33 PM on June 25, 2012 [3 favorites]

The bacteria are producing toxins, and your body is saying "goodbye" to the whole mess via the two most convenient exits.
posted by jquinby at 1:37 PM on June 25, 2012

The wiki page on exotoxins should get you started. Mechanisms vary. For example, cholera toxin ezymatically interferes with cellular signalling with the result being rapid fluid loss from the intestine. Vibrio parahaemolyticus (which can be found in seafood) is related to cholera and its toxicity mechanism is less well understood, but it also interferes with cellular signalling.

The symptoms could be evolutionarily advantageous to the pathogenic bacteria by helping them spread.
posted by exogenous at 1:49 PM on June 25, 2012 [1 favorite]

Please be sure to read about food intoxication v. food poisoning, too. They are two very distinct categories, and are often confused.
posted by halfbuckaroo at 1:52 PM on June 25, 2012

I don't think she even had food poisoning. I'm with fiercecupcake, I think she just had too much rich/fatty goods in one setting. That's a lot of sugar and fat in one meal and sometimes people's bodies just can't process it -- mine can't. Fried + fried + cake + cheese + wine sometimes = upset stomach, even if all those components are delicious and properly cooked.
posted by Countess Sandwich at 1:53 PM on June 25, 2012

Typical food poisoning actually takes more than a day to usually set in so it may not have actually been what she ate for dinner.

Some food poisoning takes a while to set in. Other types come on right quick (as some friends can attest from when they shepherded me through a long and difficult night after having some bad kebabs in Ireland once). What jquinby says about the "two exits" is indeed true of some types of poisoning, and I've even heard that you can track the contaminant through your system depending on which exit it tries to use.
posted by EmpressCallipygos at 1:55 PM on June 25, 2012 [1 favorite]

People have covered the infection vs. endo/exotoxin distinction pretty well, so I'll offer a few more possibilities:

1. It could have been scombroid food poisoning, which is caused by spoiled fish but not by bacteria itself or a bacterial toxin--it's a reaction to high levels of histamine (originating, I assume, from the fish itself, but liberated by bacterial "digestion"), which is used by humans as a local mediator of immune/allergic responses.

2. When Wikipedia mentions shellfish poisoning, they're probably talking about a group of syndromes caused by toxins originating in plankton (marine diatoms and dinoflagellates, among others, most of which are not bacteria--they're eukaryotes, like humans and scallops) and do not cause illness by infecting either you or the food you eat. Since shellfish are filter feeders, they accumulate these toxins when they're present in the water. Some kinds of shellfish poisoning are serious (some of the toxins produced by the dinoflagellates are neurotoxins) though it's possible she had diarrhetic shellfish poisoning.

But like everyone said, there are several things that could have happened, and we can't really do much more than guess.
posted by pullayup at 2:33 PM on June 25, 2012

It could have been an allergic reaction to scallops (or something else she ate) - "Allergic reactions include nausea, vomiting and diarrhea. However, these symptoms are also signs of food intolerance."

Knowing the signs and symptoms of an allergy, as well as getting clinically tested, will determine whether or not you have a scallops allergy and prevent you from experiencing a life-threatening situation. [Source: same]
posted by travelwithcats at 3:19 PM on June 25, 2012

At the time she thought it was potentially the rich food, but it's very unusual for her to throw up or even feel nauseous (think every few years [hence "iron stomach"]) so we thought it probably more likely the fish.

But these are some very interesting pointers for reading. I'm not surprised there are a lot of potential reasons for this case, but it's interesting to see how complex the idea of "food poisoning" is.

"The symptoms could be evolutionarily advantageous to the pathogenic bacteria by helping them spread."
Ah. This kind of gets to the crux of the question: whether symptoms are the goal of the bacteria or the digestive system.

It's possible she didn't have food poisoning, but after going off on a tangent discussion we're interested in learning regardless.
posted by distorte at 3:47 PM on June 25, 2012

Are these symptoms actually defences to prevent things going any further, or are they negative consequences?

It actually depends on the cause. Unfortunately I can't remember the source as I read the paper....maybe a year ago.... but scientists studied two types of bacteria that cause food/water-borne diarrhea and vomiting. I'm blanking on the details, but overall the assessment was that for one species the body's reaction was primarily health-related - the body was trying to get the pathogen out to save itself. The other organism's symptoms were classified more as spread-related - they found more infectious particles in the vomit and diarrhea or something and it was conclude the bacteria were inducing the symptoms to increase their ability to find a new host. Usually, though, the symptoms are health-related - our body's trying to protect itself and the crapiness of it is just a crappy side effect.


Does the delay between eating and feeling sick depends on bacteria multiplying?

Yes. Intoxication occurs more quickly, because this is usually the problematic part of a bacterium in our bodies. Infection takes longer, depending on the organism.

For example, most people know eating poorly canned vegetables is unhealthy, because C. botulinum is found on vegetables and canning them can lead to their growth....and as they grow they produce toxins.....so when you open that can and eat it, you're consuming a ton of toxins, which will make you sick almost immediately (same day at least). However when you eat, say, a carrot from the ground, it actually has C. botulinum on it usually, but in a form where it's not making toxins. Usually your body is strong enough to fight off the bacterium and you don't get sick. ....even if your body doesn't fight off the bacterium, it takes a few days for that bacterium to reproduce and make the toxins that made you sick.

So yeah, I think your gf suffered some intoxication from her shellfish - maybe vibrio.
posted by Lt. Bunny Wigglesworth at 5:13 PM on June 25, 2012 [2 favorites]

I heard on an episode of TWIM, sorry I don't recall which specific podcast, that Salmonella likely evolved to cause diarrhea in order to essentially create a power vacuum so that it could more effectively colonize the host.
posted by abirdinthehand at 1:46 PM on June 26, 2012