Food Poisoning

By Dr. Loretta Lanphier, ND, CN, HHP, CH

Many cases of food poisoning are so minor that they go unnoticed, but the potential exists for serious life threatening consequences in certain types of these illnesses. Educating yourself about the sources and causes of these conditions can make dining much safer and enjoyable. Let’s see what we can learn about the dangers of food poisoning, and even more importantly, how to avoid being poisoned by the foods we eat.

What is Food Poisoning?

Food poisoning, technically known as food-borne illness or gastroenteritis, is a condition that occurs after consuming food that is contaminated with bacteria, viruses, parasites, or noninfectious sources such as pesticides and other toxic chemicals. The severity of the illness can vary greatly, from barely noticeable symptoms to a potentially life-threatening situation. Foods can be contaminated at any point throughout the various stages of production, including during growing, processing, shipping, storage, and preparation.

It is thought that most people are exposed to contaminated food on a somewhat regular basis, but if the level of exposure is low and/or a person is in good general health, he or she will probably not experience any symptoms, or ones that are so minor they are not identified as being associated with food poisoning. However, people who are otherwise sick or have a compromised immune system are more likely to develop moderate or serious cases of food poisoning. The number of cases that occur annually is hard to identify, mainly because many are so mild that they are neither recognized or reported. However, the Centers for Disease Control and Prevention (CDC) estimates between 6-33 million cases per year in the United States, a number which may be artificially low.

What Are the Signs and Symptoms of Food Poisoning?

Signs of food poisoning vary from person to person and case to case, but there are some that are quite common and are likely to occur, to one degree or another, in most forms of the illness. They are very similar to influenza and other digestive tract disorders, so at times it may be difficult to be sure that what you are experiencing is food poisoning. Here is a list of some of the most common potential symptoms:

  • Nausea
  • Vomiting
  • Diarrhea (may be watery, bloody, or both)
  • Gurgling sounds in the stomach
  • Stomach cramps
  • Stomach ache
  • Fever
  • Loss of appetite
  • Fatigue

What Are the Causes of Food Poisoning?

Any foreign or infectious substance that contaminates either raw or cooked food is capable of causing gastroenteritis. The most common agent is bacteria, which accounts for most cases of food poisoning. When harmful bacteria are present in or on a food product that you consume, these “bugs” are then introduced into your body where they begin to grow and multiply. When they do this, they give off poisonous byproducts called enterotoxins that are responsible for the signs of food poisoning. These toxins can play havoc with the digestive system, resulting in the flu-like symptoms sometimes associated with food poisoning. Entertoxins are especially hard on the intestinal tract, leading to diarrhea and malabsorption of nutrients, minerals, and fluids, causing one of the hallmark symptoms of food poisoning-dehydration.

In general, most cases of food poisoning are spread by several common means:

  • Infected food handler: This typically occurs when individuals who are preparing food, either during processing or cooking, do not maintain proper hygiene by washing hands after using the bathroom. Fecal matter is a very common source of bacterial food contamination.
  • Cross contamination: This refers to unsanitary surfaces and implements used during processing or cooking that can indirectly cause bacteria to be introduced to the food product. Cross contamination may occur from a tool used at the processing plant or on the countertop or cutting board in your kitchen at home.
  • Poor food handling: If foods are not kept at proper temperatures during processing, while in transit, in storage, or when served, food poisoning can result. Examples would be a bad freezer on the truck that delivers food to the grocery store, or leaving dishes out during a picnic that should have been refrigerated or kept hot.
  • Contaminated water or soil: This is a common problem for fresh fruit and vegetable products. Cases have occurred where food poisoning was traced to the water used in irrigation, or even from livestock or field workers who defecated near the crops.

The way food poisoning affects an individual has everything to do with the type of agent that is responsible for the infection. Perhaps the best way to understand how food poisoning occurs is to take a look at some of the most common forms of contaminants that can trigger it. Let’s start with bacteria, as they are the culprits behind most cases of food-borne illness.


This form of bacteria often attacks meat, poultry, eggs, or milk. If these foods are undercooked, salmonella can survive. Source is often human or animal feces. Typically spread through cross contamination or via infected food handlers. Salmonella poisoning usually exhibits signs about 12-72 hours after eating contaminated food, and may result in such symptoms as vomiting, diarrhea, and fever.

Escherichia coli

Also known as E. coli, it typically appears in beef that is contaminated during slaughter or processing, or in milk, water, apple cider, or ready-to eat vegetables such as salads or alfalfa sprouts. The most common strain is called E. coli 0157:H7, and it is slower to produce symptoms than some other forms of food-borne illnesses. Signs usually occur within one to three days after exposure, and some of the distinguishing symptoms may be bloody diarrhea and severe abdominal cramps. Because of the bloody diarrhea, which may last up to eight days or so, E. coli infection is sometimes called hemorrhagic colitis. Dehydration is a common complication with these types of infections.


Infected chicken, which often occurs if the poultry is exposed to fecal matter during processing, is the most common source of this bacterial agent. It can also be found in contaminated water or milk. This is also an illness that takes a while to show itself, with signs typically occurring two to five days after consuming infected products. Along with the usual food poisoning symptoms, watery and / or bloody diarrhea is common, making dehydration a risk. The illness usually lasts from 7-10 days, and it is not uncommon for relapses to occur.

Staphylococcus aureus

Also known as staph infection, this bacteria can be found in meat, raw salads, gravies, sauces, and cream-filled pastries. It is transmitted most often through infected food handlers who have staph skin infections or who cough / sneeze on foods. It occurs very rapidly, within 2-8 hours after exposure, and symptoms typically last only 3-6 hours. Generally mild infections that cause minimal discomfort.


This bacterial agent is most often found in raw salads and ready-to-eat produce products. It is usually spread by infected food handlers. Symptoms appear within 72 hours and may last several days. Shigella is a bit unique among food-borne illnesses in that it may exhibit neurological symptoms alongside the standard food poisoning signs, especially in kids. Severe infections in children result in headache, fatigue, stiff neck, confusion, and even seizures.

Clostridium botulinum

This is the culprit responsible for botulism, the most serious and life threatening form of bacterial food poisoning. It is most often contracted from improperly canned or preserved foods. It usually appears within 72 hours after exposure, but there have been some cases that did not produce symptoms until up to eight days later. The signs are unique in that botulism does not typically involve vomiting or diarrhea, but does exhibit neurological symptoms such as double vision, difficulty speaking and swallowing, and difficulty breathing. In severe cases, death may result from respiratory failure due to paralyzed muscles in the respiratory tract.

A special note about infant botulism: Never give honey to children younger than one or two years old, as spores of a certain form of botulinum bacteria can be present in honey. Their immune systems are not mature enough to fight off these spores, and botulism infections can be fatal to young children.

Other Toxins

Certain types of tropical fish have neurotoxins present in their bodies that can cause food poisoning. These include groupers, snapper, mackerel, and barracuda.

Pufferfish or Blowfish, also known as fugu, is a Japanese delicacy that is often associated with macho behavior in individuals who knowingly eat this dangerous fish and tempt fate. The result is often severe illness or death. Fast acting neurotoxins in blowfish can cause death due to heart failure, coma, or respiratory paralysis within minutes or hours after eating this toxic food.

Shellfish can also be hazardous either due to poor handling and preparation, or due to certain algae that are eaten by the creatures. If you ever see shellfish that has a reddish tint to its body or are harvesting them in reddish waters (called red tide), do not consume these products. They are likely contaminated and may cause food poisoning. Typical symptoms may occur, but neurological symptoms are also possible that can be life threatening in extreme cases.

Mushrooms can also be poisonous, and a few are even deadly. Be very careful if you forage for mushrooms. It can be quite difficult to tell the difference between safe species and harmful ones.

Chemical Sources of Food Poisoning

The most common source of food-borne illness from chemical sources is the consumption of foods containing hazardous pesticides and insecticides. Be sure to thoroughly wash fruits and vegetables before eating. This habit can protect you from other sources of food poisoning as well, such as from bacterial agents that may be on the surface.

Also be aware of potential lead or arsenic poisoning from foods stored or packaged in toxic containers. Be especially careful of products that are imported from foreign countries.

How Can Food Poisoning Be Treated or Prevented?

If you should develop a case of food poisoning, most of the time it will be minor and simply run its course. Watch out for excessive diarrhea and potential dehydration, the most common serious complication of food-borne illnesses. However, be aware of any symptoms that seem severe or ongoing, especially if you suspect exposure that may lead to serious consequences. The young, the elderly, and individuals who have compromised immune systems are at the greatest risk for serious infections.

Prevention is by far the best option, as it is with any illness. Be sure to use the best sanitary practices you can when you are preparing and eating your own food. If you are not eating at home, choose your restaurants carefully, and never drink water or other beverages, especially in a foreign country, that are not bottled (remember Montezuma’s revengeā€¦?).

Take responsibility for what you do or do not put into your body, and don’t take anything for granted. The risk of food poisoning will diminish greatly if you avoid such foods as meat and seafood, and religiously wash all raw produce before eating.

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