I was always taught that chicken and eggs, if consumed raw, will lead to salmonella 100% of the time. In my experience I have found this to be patently untrue (not surprisingly). While I always strive for hygenic food preparation and adequate cooking times, sometimes I goof up and end up eating chicken which is less than fully cooked. Additionally, I have never met someone who has contracted salmonella after eating raw cookie dough.

When buying chicken or eggs from a modern American grocery store, what is the real risk of contracting salmonella from under cooked products? (i.e. If I eat 1,000 raw chicken breasts, how many terrible nights will I have?)

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    "I was always taught that chicken and eggs, if consumed raw, will lead to salmonella 100% of the time. " - I have no idea who taught you that, but common myths such as this one are the reason why so many people are misinformed about food safety and end up using dangerous practices. Rant aside, while the risk of actually getting sick is impossible to predict at all, there are data about salmonella contamination, and that's quite high with modern hygiene practices, which are quite bad overall. I'll try finding actual numbers to make an answer. – rumtscho Jan 14 '16 at 16:34
  • To be fair, i often eat raw or almost raw eggs, which is pretty common where i am from. I have had salmonella from chicken that wasn't sufficiently cooked though. Eggs and meat are miles apart in my opinion. – Max Jan 14 '16 at 17:11

If I eat 1,000 raw chicken breasts, how many terrible nights will I have?

Impossible to say. You will ingest many pathogenic bacteria, but nobody in the world can predict how many times they will cause an illness, and in how many of these times the symptoms will be noticeable, and how many nights each case will take until you heal.

What is easy to measure is the actual contamination rate of meat. Here is one study which was done in American food: http://www.consumerreports.org/cro/magazine/2014/02/the-high-cost-of-cheap-chicken/index.htm. They found that 13.6% of the chicken breasts were contaminated with salmonella (out of a sample of 300). So, if salmonella is the only thing you are worried about, expect to come in contact with pathogens 130 times out of 1000 raw chicken meals. Again, the "falling ill" rate in these cases won't be 100%.

On the other hand, being worried about salmonella exclusively is not wise. There are a ton of other pathogens on chicken. The same study found that

Almost none of the brands was free of bacteria

and, even worse,

About half of our samples (49.7 percent) tested positive for at least one multidrug-­resistant bacterium.

So, while you will be exposed to salmonella from only 13.6% of your hypothetical raw chicken meals, you will be ingesting pathogens with each of them. You won't fall ill every time you do it, but it's highly unlikely that it will be zero times either.

This is just one article, but I have in the past read other studies which found similar numbers of contamination in other first world nations.

I also recommend reading the whole article I linked, it contains much more interesting information than simply numbers on contamination.

A side note on why I called your belief dangerous: We have very many food safety questions here, and I see all the time answers like "I ate it and nothing happened, so this practice must be safe". NO! Once you realize that unsafe food won't make you ill 100% of the time, and not even 10% of the time, you know not to mistakenly declare unsafe practices "safe" just because you got lucky a few times.

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    Exactly. It's like declaring Russian roulette kills in 100% of the cases, or it's safe practice, depending on the end result of your first run. – Willem van Rumpt Jan 14 '16 at 17:57
  • always wondered if not every being exposed to the bateria will make us more suspect-able to death from it; as our body doesnt have anti-bodies. Could someone build a tolerance; ie; many countries that eat raw eggs and never have an issue. – zerobane Jan 14 '16 at 18:26
  • @zerobane I don't know how much antibodies are worth it in this case, I'd let the experts decide it. "Countries that eat raw eggs and never have an issue" sounds like a very strong claim. Do you have any statistics for it? To my knowledge, all countries have outbreaks of foodborne illness, plus a ton of cases which never get reported because people just stay at home. – rumtscho Jan 14 '16 at 18:30
  • @zerobane Foodborne illnesses are not an infections by the bacteria that contaminate the food. Rather, it is a toxic reaction to the waste product left behind by microbial activity on the contaminated food. One can develop a tolerance for those toxins, but it is not an immune response. – Sean Hart Jan 14 '16 at 20:06
  • @SeanHart to be fair, both scenarios are found in reality. Either lots of bacteria live in your food and produce toxins there -> you eat it -> you get sick, or a few bacteria live in your food -> you eat it -> they start making colonies in your body and excreting toxins in it -> you get sick. Immunity can prevent the second scenario from happening. But the immune system is a very complicated thing, and 1) I don't know if people can develop immunity to the relevant microorganisms in this case, and 2) if they can, it will prevent some, but not all, cases. – rumtscho Jan 14 '16 at 20:10

In summary, it's complicated, as rumstcho's answer indicates. And the number of infected chickens/eggs is only the beginning, since chances of illness depend on how high the bacteria count is. There need to be enough to survive ingestion and partial digestion before they can incubate in your body and then cause illness.

Thus, to predict chances of illness from "undercooked" chicken or eggs, you would need to consider:

  • The rate of contamination on raw products at the grocery store
  • Storage and food preparation conditions, including temperature, duration of storage, and possibilities for cross-contamination
  • Growth rate of bacteria depending on whether the prepared food is a good growth medium (liquid or dry, whether a good food source for bacteria, etc.) after preparation has begun
  • If partially cooked, temperature and duration spent below 130F (particularly in maximum growth range around 100F)
  • Time and temperature spent above 130F (which will gradually reduce bacterial population)
  • Amount of food ingested
  • Health condition, age, immune system status, etc. of person eating the food
  • Etc.

There are simply too many variables. Most of the chicken in the grocery store probably has the potential to cause illness, but whether it will happen depends a lot on what exactly you do with it.

What we do know is that there are likely 1-1.5 million cases of Salmonella poisoning in the U.S. every year. This is an estimate because the vast majority of cases are not reported -- perhaps the illness isn't severe enough or people assume it's a "virus" or something else and don't get tested.

The FDA estimates that 142,000 cases of illness are caused each year in the U.S. by eggs infected with Salmonella alone. Most Salmonella poisoning associated with eggs comes from people mishandling them after they're out of the shell, since most estimates say only about 1 in 20,000 eggs is internally infected with Salmonella. (The rest of infected eggs have Salmonella on the shell; in the U.S., most of this is washed off, but regardless it still wouldn't cause illness on the shell until the bacteria have time to be mixed in a better growth medium and to propagate before consumption.) Still, given that the U.S. consumes around 75 billion eggs each year, that's still a lot of potentially infected eggs.

And just because you ate your chicken "undercooked" doesn't necessarily mean it was likely to still have enough bacteria to make you sick. The USDA/FDA recommends 165F as a safe final temperature for poultry because that's where Salmonella will mostly die in a few seconds. But if you were roasting a chicken and it spent a long time above 130F, bacteria will gradually die off. You could potentially still eat a chicken that had spent over an hour at 140F and was pink and "squishy" (and unappetizing to many people), but enough bacteria may have been killed by that point to make illness unlikely.

But that doesn't mean you could have safely eaten it raw or at room temperature or before it got to 130F or before it spent a long time above that temperature. It's the whole food preparation process that dictates the chances of illness.

Lastly, I would just note the phrase "how many terrible nights will I have" in the question, which to me sounds like it's referencing "stereotypical food poisoning" -- where you get sick a few hours later and have a little diarrhea or vomiting overnight and then get better within 24 hours or so. That's often not due to Salmonella; there are lots of other bacteria and toxins in food that can cause such illnesses.

Salmonella infection is sometimes mild in healthy adults, but it's usually not the sort of thing that just causes a single "bad night" of "stereotypical food poisoning." While symptoms can appear quickly, it could take up to 2-3 days for them to appear, and they usually last for quite a while -- typically 4-7 days.

Also, many foodborne illnesses can take several days or even more than a week to incubate before you show symptoms, so that "stereotypical food poisoning" might even be from something you ate days ago.

Bottom line: short of a lab test on the food you ate and a stool sample, you can't know whether a particular food caused illness. And given that most food poisoning cases are mild and/or could be days removed from ingestion, people tend to draw misleading conclusions about what foods caused problems, if they even consider it an "illness" at all.

But that doesn't mean foodborne illness doesn't exist or is incredibly rare. The CDC estimates that roughly 1 in 6 Americans (~50 million people) will experience some form of foodborne illness each year. You may just not realize what it is or what caused it.

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