People are freaking out about a recent story where a man who ate sushi ended up with a stomach parasite. While acquiring a gut buddy is a real possibility whenever you eat something raw, it’s also fairly uncommon and easy to avoid.
The parasite in question, anisakiasis, is a nematode (or worm) larva that attaches to the wall of your esophagus, stomach, or intestine. They live in raw fish and squid, but they rarely cause health problems in humans because they either pass through the intestine without latching on, or they aren’t able to survive in your harsh gut environment. Even if a nematode makes itself at home inside of you, it won’t live longer than 10 days or so. Those 10 days will be very uncomfortable, though. And while it’s true that cases of parasites are on the rise, it’s only because sushi’s popularity continues to skyrocket. The best way to avoid getting them, of course, is to not eat sushi or sashimi, but screw that—it’s delicious. And honestly, you don’t have to worry so much.
Why You Shouldn’t Worry Too Much
All raw fish can have parasites, but not all raw fish does—especially when you’re eating at a well-established sushi restaurant. Why? That fish you’re eating was flash frozen solid at a temperature of -35°F and stored that way in a commercial freezer for at least 15 hours to kill whatever parasites happened to be in it.
That’s right. Your sushi is probably not fish that was caught that morning. In fact, most states—like Oregon—require it be frozen first. But that’s a good thing! Beyond banishing parasites like anisakiasis and tapeworm, raw fish actually has better flavor after it has been aged a little. Other than cooking the fish all the way through, freezing it is the best way to prevent parasites.
Your favorite sushi joint also probably buys their fish from a seafood processor, which inspects the fish before it’s sold. Using a process called “candling,” they shine light through the fillets to look for any abnormalities, including bones. Then they either remove them or discard the fish. If you’re playing the home game, you can do this easily enough yourself using a very bright flashlight. Furthermore, that seafood processor probably get a lot of their product from fish farms, which is less likely to be riddled with worms. Multiple studies have found that fish from hatcheries have far fewer incidents of parasites, while wild-caught fish can have a very high rate of infection.
How You Can Be Proactive
If all that information isn’t enough to keep you from being freaked out, here are a few other tips you can follow to keep your gut parasite-free:
Do a little research: Find reputable sushi restaurants and ask them where they get their fish. Is the seafood processor known for quality? Is the fish the restaurant serves farmed or wild-caught? Do they freeze their fish according to FDA regulations? They’ll likely be more than happy to tell you the great lengths they go for quality food. Remember, sushi chefs are trained for years to deliver you delicious fish that’s safe to eat. If they don’t, they go out of business.
Freeze and candle your own fish: If you’re preparing sushi or sashimi at home, you’ll have to be patient. You should buy thinly-sliced “sashimi-grade” fish at a reputable market, candle it, and pop it in the freezer for a whole week since it can only get to about -4°F. At that temp, it takes a lot longer to kill everything off. It was probably already flash frozen, but better safe than sorry.
Learn to spot worms: Worms in raw fish are usually pretty obvious, especially in thinly cut pieces of sashimi. They look like long, thin strands of red, white, pink, or brown, and are, uh, usually moving... But if you’re curious what they look like, here is a worm in some tuna, here is a worm in some salmon, and here is a worm in some yellowtail. Also, here is a video of a woman casually removing worms from some monkfish. Be warned, though, these videos will help you identify worms, but they’re also really gross.
Almost all fish have parasites of some kind, but very few them ever make it to the plate. And even if they did, very few of the ones that affect fish also affect people. The bacteria found on food is far more dangerous overall, and that’s a risk you take eating any food at any restaurant out there. That said, raw seafood is best avoided by pregnant women, the elderly, young children, and those with compromised immune systems. But if you’re fit as a fiddle, don’t be scared! Arm yourself with knowledge, know what to look for, and dig in.