One Less Thing to Worry About: Undercooked Pork

Harriet Hall

We have plenty of things to worry about: the pandemic, global warming, the economy, racial tensions, and much, much more. But here is some good news to ease the worry burden: you can stop worrying about eating undercooked pork. 

Most people agree that undercooked pork is bad, but not everyone can explain why. The “why” is a nasty little parasitic worm called Trichinella that can cause the disease trichinosis, also called trichinellosis and trichiniasis. Dietary laws in Judaism, Islam, and some other religions prohibit eating pork; this was once thought to be based on health considerations, but that hypothesis has fallen out of favor. Anthropologist Marvin Harris thought the religious prohibitions were a response to ecological and economic factors rather than health risks. I’m going to discuss the evidence for the claim that eating undercooked pork is risky. If you follow religious prohibitions and avoid all pork, you might as well stop reading now.

Trichinella’s Life Cycle

It usually goes like this: A pig or a human eats meat that contains trichinella cysts. That might happen if pigs eat the carcasses of infected rats or are fed with raw meat garbage or if humans eat infected pork that is undercooked. Digestion in the stomach releases the trichinella larvae from the cysts, and the larvae travel to the small intestine, where they molt four times over a little more than a month to become adult worms. They then mate and produce new larvae. The adults are pooped out of the intestinal exit door and die, but the larvae pierce through the intestinal mucosa, enter the lymph and the blood stream, and travel throughout the body. For most sites of the body, landing there will kill them. However, the lucky ones that end up in skeletal muscle can encyst and survive. There they wait for the host to die and for its muscles to be eaten by another animal so the cycle can continue. Can you imagine all those worms and larvae and cysts being inside your body? Are you grossed out yet?

Symptoms, Diagnosis, and Treatment

If you ingest fewer than seventy larvae, you may have no symptoms and might never know you were infected. If you ingest between seventy and 150 larvae, you may develop gastrointestinal symptoms a couple of days later, with diarrhea and abdominal pain. In a later parenteral phase, you might develop fever, muscle pain, swelling around the eyes, and a high eosinophil count. Trichinosis is diagnosed by blood tests or muscle biopsy, but both may give false negative results early in the course of the disease. And antibodies can persist for years, so a positive blood test may not indicate a current infection. If you are diagnosed with trichinosis, it’s not the end of the world; treatment with the anti-parasitic drug albendazole is effective if taken early in the course of disease. If it’s too late for albendazole to get the job done, there’s no need for panic; even without treatment, the symptoms will usually resolve on their own within a few months.  Complications in heavy infestations can occur, with myocarditis, encephalitis, meningitis, pneumonia, and even death.  But such outcomes are exceedingly rare.

Drastic Decline of Incidence in the United States

In 1980, Congress passed the Federal Swine Health Protection Act, which prohibited feeding swine with trichinella-contaminated food. Other measures have helped, such as inspections, animal testing, rodent control, limiting commercial pigs’ contact with wildlife (free-range practices increase risk), improved hygiene, and immediate removal of dead pigs from pens. The incidence of trichinosis remains high in many countries, especially China, where 10,000 cases of trichinosis are reported every year. But in the United States, trichinosis has been eliminated for all practical purposes. Trichinosis is a reportable disease. The CDC tracks cases and publishes the results of its surveillance activities in the Morbidity and Mortality Weekly Report (MMWR). From 2008 to 2012, a total of ninety cases were reported—a mean annual incidence of less than one-tenth of one case per million people. Meats other than pork, including meat from bears and deer, accounted for more than half of the cases—and two were even linked to ground beef (Did you know hamburgers can give you worms?). Several cases were linked to wild boar and home-raised swine. Many other animals are known to harbor trichinella, including horses, walruses, and many other animals whose meat is not sold in U.S. supermarkets.

In 2008, there was an outbreak of trichinosis in northern California caused by consumption of undercooked bear meat. The attack rate was high: of thirty-eight people attending an event where the bear meat was served, thirty became sick. The bear in question had been shot while lying down and had appeared to be sick. There’s a lesson in that for hunters.

So developing trichinosis from eating undercooked pork is not impossible in the United States, but the overall risk is an order of magnitude less than one in a million. And the risk is much less if you avoid eating the meat of wild animals, especially bear meat. Note: freezing pork will kill the trichinella organisms, but freezing bear meat won’t.

What Degree of Risk Is Reasonable?

A micromort is a unit of risk defined as a one-in-a-million chance of death; a microprobability is a one-in-a-million chance of some event. Most people are willing to accept a one-in-a-million risk. Skiing incurs a risk of 0.7 micromorts per day; running a marathon carries a risk of 7 micromorts per run; hang gliding, 8 micromorts per trip; scuba diving, 5 micromorts per dive; giving birth, 120 micromorts; and traveling increases the risk by one micromort when you travel 1,000 miles by jet, 230 miles by car, ten miles by bicycle, or even seventeen miles by walking. 

In comparison, the risk of dying from eating undercooked commercial pork products in the United States is far less than one micromort, and the risk of developing trichinosis is well below one microprobability. 

Current Cooking Guidelines

Recommendations for cooking pork have been revised. Official guidelines no longer require us to cook all pork to 160 degrees. Now they say it is sufficient to cook common cuts of pork to an internal temperature of 145 degrees Fahrenheit followed by a three-minute rest after removal from the heat source (during which the temperature will continue to rise for a short time). The resulting product will be pinker than most home cooks are used to. However, 160 degrees is still recommended for all ground meats.

“It’s great news that home cooks can now feel confident to enjoy medium-rare pork, like they do with other meats,” said Guy Fieri, a chef, restaurateur, and host of several food-focused television programs. “Pork cooked to this temperature will be juicy and tender. The foodservice industry has been following this pork cooking standard for nearly ten years.”

The Bottom Line

There’s a long list of things that I might legitimately worry about (not that worry ever did any good!), but I have taken undercooked pork off my list. I no longer worry if I detect a tinge of pink in my pork chop. Guy Fieri is right: pork does taste better when it is medium-rare. It’s a relief to have one less thing to worry about, and I enjoy my meals more. You can too. Relax! Bon appétit!

Harriet Hall

Harriet Hall, MD, a retired Air Force physician and flight surgeon, writes and educates about pseudoscientific and so-called alternative medicine. She is a contributing editor and frequent contributor to the Skeptical Inquirer and contributes to the blog Science-Based Medicine. She is author of Women Aren’t Supposed to Fly: Memoirs of a Female Flight Surgeon and coauthor of the 2012 textbook Consumer Health: A Guide to Intelligent Decisions.