By Jason Masters
Environmental Health Director
Q: Hi Jason. Why is sushi so gross? I would NEVER eat anything that was raw, especially fish! How in the world did people decide that eating raw fish would be a good idea? And what do all those other words mean? Sashimi. What’s that?!? Nigiri? How do I even pronounce that?!? Don’t people get really sick from that stuff?
Glad you asked April. Let’s talk about sushi. One of American cuisines biggest challenges, and a mystery to almost everyone. A Japanese staple since the ninth century, sushi is a term that really doesn’t mean what most people think of when sushi is mentioned. Sushi is actually the preparation and combination of ingredients with rice and vinegar. Sashimi (Sa-SHE-me) is usually confused with the term “sushi” and means thinly sliced, raw fish sometimes served with daikon radish or other ingredients. Nigiri (Ni-GEAR-ee) is raw fish served on a small bed of rice. What most people think of when they hear sushi is the maki (MA-key) roll. Rice with seaweed (nori) rolled up with avocado, fruit, crab, fish etc. topped with thin slices of fish and/or roe. It is important to note that there are a million varieties of this, and every restaurant may have a different term for what they call something.
The important thing to know about the safety of sushi is how the fish and rice are handled. In NC, most sushi grade fish is supplied to restaurants from suppliers that have frozen the fish to a temperature of -4 degrees F, and held for 168 hours (7 days). This will effectively kill any parasites that may be present in the fish. Additionally, each food establishment that serves sushi is required to maintain a “parasite destruction form” on site, from the supplier of the fish. Yellowfin, bigeye, northern and southern Bluefin tunas are exempt from the parasite destruction requirement. Rice is handled in a variety of ways. If sushi rice is too hot, it can’t be rolled or formed correctly. If it is too cold, same problem. From a food safety standpoint, we have issues with food (in this case, the rice) being held at room temperature. Therefore, establishments can either choose to create a plan called a HACCP (Hazard Analysis Critical Control Point) plan, that will allow them to add enough vinegar to reach a certain pH so they can leave the rice out for an extended period of time, or they can choose to use time as a public health control (TPHC) which will allow the establishment to keep the rice out of temperature for a period of not more than 4 hours, and is then discarded. Either way is an accepted method, and these are items that are reviewed at each inspection. So, theoretically, sushi, if prepared and handled correctly, is safe.
So let’s talk a little about what makes people sick from sushi. Just a warning before we start…it’s not pretty…
The most common illness associated with eating sushi and other raw or undercooked seafood is anisakis (annie-SOCK-us) simplex. Basically, anisakis is a nematode, or in regular people terms…a worm. It is present on certain types of fish, and through mishandling of fish products after harvesting, it can make its way from the flesh of the fish to the muscle. It is a parasite that is destroyed by freezing at a certain temperature for a certain period of time (there won’t be a test on this, but we covered it above…). So let’s say you eat your favorite maki roll, and it just so happens it is infected with a herring worm…what happens next?
Well, first, the worm you ate is going to attach itself to your intestinal walls, where it will make a home for itself, and begin enjoying its new surroundings. You may notice symptoms in as little as one hour, up to two weeks. Symptoms may include the normal feelings of queasy-ness, up to feelings associated with appendicitis, or you may experience a tingling or tickling sensation in your throat… (In the literary world, this is known as foreshadowing)… So when you get back from vacation, make sure to remember the name of that cute, little out-of-the-way sushi place that the locals recommended… The worm can detach and reattach as often as it likes. After you vomit up, or manually extract (think about that for a second) the matured worm, you can take it to the doctor just to verify that you actually did get it from the raw fish you ingested… (I can only imagine what my doctor would say if I brought that to him in a jar)… In some cases, the doctor may have to use a camera device to look around inside your stomach and intestines to verify the presence of the nematode. An infection can be very painful and if the worm is not removed manually or involuntarily, then surgery may be the only course of action….
I know…awful, right?
The good news is that only about 10 cases are diagnosed each year in the U.S. (that’s 0.2 per state, for all you math nerds) however, there is some suspicion that not all cases are reported. So, the takeaway here is that, though very rare, it is possible to become sick from raw fish. Anisakis is most commonly associated with cod, haddock, fluke, pacific salmon, herring, flounder, and monkfish. Remember those species I mentioned above that are exempt from the parasite destruction form? Well, I’m not going to tell you what to eat, but I know the rolls I’m going to pick. By the way, I know this cute, little out-of-the-way place that has great sushi…you should totally check it out…