Some of the most dangerous organisms in the world don’t bite or sting—they enter quietly through what we eat and drink.
The most common culprits are tapeworms like Taenia solium and Diphyllobothrium, roundworms such as Trichinella spiralis and Anisakis, and protozoa including Toxoplasma gondii, Giardia lamblia, and Cryptosporidium. Unlike many bacteria, these parasites can survive refrigeration and light cooking.
Once inside the body, they can remain alive for months or even years, migrate to organs, muscles, or the brain, and trigger chronic digestive problems, fatigue, and nutrient deficiencies. According to the World Health Organization, more than 3.5 billion people worldwide are affected by parasitic infections each year.
Undercooked meat is one of the most common sources. Raw or lightly cooked pork can carry roundworms and pork tapeworms, leading to trichinosis or even cysts in the brain. Rare beef and steak tartare may contain beef tapeworms that cause abdominal pain and weakness. Raw or lightly prepared fish, including sushi and ceviche, can harbor worms that cause severe stomach pain, vomiting, and allergic reactions. Pork should reach 145°F with a rest period, ground beef 160°F, and fish 145°F or until opaque and flaky. Raw pork is never safe, and while sushi-grade fish is frozen to reduce risk, it is not foolproof.
Raw or undercooked shellfish are another danger. Oysters, clams, and mussels filter polluted water and can absorb parasites such as liver flukes and protozoa. Raw shellfish have been linked not only to bacteria and viruses but also to parasitic infections. They should always be cooked until the shells open and the flesh turns opaque. People who are pregnant or immunocompromised should avoid them entirely.
Unwashed fruits and vegetables can also carry hidden threats. Produce grown in contaminated soil may harbor parasites like Toxoplasma, Giardia, and Cyclospora. These can cause serious illness, especially during pregnancy. All produce should be washed under running water, firm skins scrubbed, and leafy greens soaked and cleaned thoroughly. A quick rinse is not enough.
Unpasteurized dairy products, including raw milk and soft cheeses, can contain parasites that survive cold temperatures. Choosing only pasteurized dairy is one of the simplest and safest protections, and pregnant women should avoid raw dairy completely.
Contaminated water is a major global source of infection. Drinking unsafe water, brushing teeth with it, or washing food in it can introduce parasites such as Giardia, Entamoeba histolytica, and Cryptosporidium. These risks are especially common while traveling. Using bottled or filtered water, boiling when in doubt, and avoiding ice in high-risk areas can prevent serious illness.
Protection comes down to a few habits: cook meat thoroughly, freeze fish before eating it raw, wash all produce carefully, avoid raw or undercooked meat and seafood, and drink only clean water.
Staying healthy does not require fear—only awareness. Sometimes safety is as simple as one more minute of cooking, one careful wash of lettuce, or the choice to wait until food is truly safe. Real wellness is about respecting what you can’t see and protecting your body with intention.
So when you enjoy that steak, sushi, or salad, you’ll know you didn’t just eat—you protected yourself.