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11.20: Digestive System Health

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    Have you ever been sick to your stomach?

    You may have even had to stay home from school because of a "stomach bug." It is possible that you caught a contagious illness, or you could have gotten sick from food you had eaten recently. The symptoms are very similar, so it's hard to pinpoint the cause.

    Health of the Digestive System

    Most of the time, you probably aren’t aware of your digestive system. It works well without causing any problems. But most people have problems with their digestive system at least once in a while. Did you ever eat something that didn’t “agree” with you? Maybe you had a stomachache or felt sick to your stomach? Maybe you had diarrhea? These could be symptoms of foodborne illness, food allergies, or a food intolerance.

    Foodborne Illness

    Harmful bacteria can enter your digestive system in food and make you sick. This is called foodborne illness or food poisoning. The bacteria, or the toxins they produce, may cause vomiting or cramping, in addition to the symptoms mentioned above. Foodborne illnesses can also be caused by viruses and parasites. The most common foodborne illnesses happen within a few minutes to a few hours, and make you feel really sick, but last for only about a day or so. Others can take longer for the illness to appear. Some people believe that the taste of food will tell you if it is bad. As a rule, you probably should not eat bad tasting food, but many contaminated foods can still taste good.

    You can help prevent foodborne illness by following a few simple rules.

    • Keep hot foods hot and cold foods cold. This helps prevent any bacteria in the foods from multiplying.
    • Wash your hands before you prepare or eat food. This helps prevent bacteria on your hands from getting on the food. This is the easiest way to prevent foodborne illnesses.
    • Wash your hands after you touch raw foods, such as meats, poultry, fish, or eggs. These foods often contain bacteria that your hands could transfer to your mouth.
    • Cook meats, poultry, fish, and eggs thoroughly before eating them. The heat of cooking kills any bacteria the foods may contain, so they cannot make you sick.
    • Refrigerate cooked food soon after a meal. Cooked food can be left out for up to two hours before they need to be placed in the cold. This will prevent the spread of bacteria. Cooked foods should not be left out all day.

    Bacteria that cause foodborne illnesses include Salmonella, a bacterium found in many foods, including raw and undercooked meat, poultry, dairy products, and seafood. Campylobacter jejuni is found in raw or undercooked chicken and unpasteurized milk. Several strains of E. coli can cause illnesses, and are found in raw or undercooked hamburger, unpasteurized fruit juices and milk, and even fresh produce. Vibrio is a bacterium that may contaminate fish or shellfish. Listeria has been found in raw and undercooked meats, unpasteurized milk, soft cheeses, and ready-to-eat deli meats and hot dogs. Most of these bacterial illnesses can be prevented with proper cooking of food and washing of hands.

    Common foodborne viruses include norovirus and hepatitis A virus. Norovirus, which causes inflammation of the stomach and intestines, has been a recent issue on cruise ships, infecting hundreds of passengers and crew on certain voyages. Hepatitis A causes inflammation of the liver, which is treated with rest and diet changes. Parasites are tiny organisms that live inside another organism. Giardia is a parasite spread through water contaminated with the stools of people or animals who are infected. Food preparers who are infected with parasites can also contaminate food if they do not thoroughly wash their hands after using the bathroom and before handling food. Trichinella is a type of roundworm parasite. People may be infected with this parasite by consuming raw or undercooked pork or wild game.

    Food Allergies

    Food allergies are like other allergies. They occur when the immune system reacts to harmless substances as though they were harmful. Almost ten percent of children have food allergies. Some of the foods most likely to cause allergies are shown below (Figure below).

    Eating foods you are allergic to may cause vomiting, diarrhea, or skin rashes. Some people are very allergic to certain foods. Eating even tiny amounts of the foods causes them to have serious symptoms, such as difficulty breathing. If they eat the foods by accident, they may need emergency medical treatment.

    Many foods, such as milk, shellfish, nuts, grains, and eggs can cause allergies
    Figure \(\PageIndex{1}\): Some of the foods that commonly cause allergies are shown here. They include nuts, eggs, grains, milk, and shellfish. Are you allergic to any of these foods?

    The most common food allergy symptoms include:

    • tingling or itching in the mouth
    • hives, itching or eczema,
    • swelling of the lips, face, tongue and throat, or other parts of the body,
    • wheezing, nasal congestion or trouble breathing,
    • abdominal pain, diarrhea, nausea or vomiting,
    • dizziness, lightheadedness or fainting.

    In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or death. Anaphylaxis is vary rare. The vast majority of people will never have an anaphylactic reaction. The life-threatening symptoms of anaphylaxis include:

    • constriction and tightening of the airway,
    • a swollen throat or the sensation of a lump in your throat that makes it difficult to breathe,
    • shock, with a severe drop in blood pressure,
    • a rapid pulse,
    • dizziness, lightheadedness or loss of consciousness.

    Food Intolerance

    food intolerance, or food sensitivity, is different from a food allergy. A food intolerance happens when the digestive system is unable to break down a certain type of food. This can result in stomach cramping, diarrhea, tiredness, and weight loss. Food intolerances are often mistakenly called allergies. Lactose intolerance is a food intolerance. A person who is lactose intolerant does not make enough lactase, the enzyme that breaks down the milk sugar, lactose. Lactose intolerance may be as high as 75% in some populations, but overall the percentage of affected individuals is much less. Still, well over 10% of the world's population is lactose intolerant.


    • Foodborne illness can be prevented by taking precautions during food preparation.
    • Food allergies and food intolerance can upset your digestive system.

    Explore More

    Use the resources below to answer the questions that follow.

    1. What is a food allergy? How does the body respond to food allergies?
    2. What does the phrase "dose related" mean? How does this relate to food intolerance?
    3. What are four common symptoms of food allergies?
    4. What are the eight most common food allergens?
    5. Do all people of all ages respond in the same way to foods?


    1. List two rules that can help prevent foodborne illness.
    2. What's the difference between a food allergy and a food intolerance?
    3. List three foods that commonly cause allergies.
    4. List three common symptoms of food allergies.

    This page titled 11.20: Digestive System Health is shared under a CC BY-NC license and was authored, remixed, and/or curated by CK-12 Foundation via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.