"Irashaimase!" My family has become obsessed with sushi. For many years, my most adventurous foray was a California Roll. Thanks to a friend's persistence, now even my youngest daughter will, without hesitation, reach for eel before her napkin hits her lap. It has been a fun transformation to watch, but it has also raised a whole set of questions about the risks and benefits of eating raw fish. So, sushi is today's topic, and "Irashaimase!" is the greeting you may hear as you enter a sushi bar.The Japanese have eaten sushi for centuries, but sushi as we know it originated as a fast-food option in Edo, Japan, in the mid-19th century. Customers ate it with their hands or carried it with them as they went to the theater. Visit a sushi cart or restaurant today, and you'll see two main kinds of rolls: nigiri and maki. Nigiri consists of a mound of vinegared rice topped with a dab of hot wasabi (horseradish) and a slab of fish, crab, egg, or other topping. A small, thin bamboo mat is used to roll maki, a cylinder of rice wrapped in nori (seaweed). Sushi comes in such a staggering variety that it's common to use a pictorial glossary when ordering. Because of this diversity, the nutritional value of one item to the next varies. In general, fish provides a lean source of low-calorie, high quality protein. It's also low in saturated fats and cholesterol, making it a heart-healthy food choice. Should we be concerned, however, that much of the fish used in sushi comes from deep cold water, where fish tend to have more fat? Fortunately, that fat is Omega-3 of both the DHA and EPA types. Both of those are utilized in the development of the central nervous system, and since we don't manufacture it, it must be consumed. Also note that DHA is involved in the development of the "good" cholesterol, HDL, and consuming DHA not only increases the level of HDL, it also decreases the level of LDL, the "bad" cholesterol. DHA also appears to help maintain normal blood sugar levels. Further studies are examining the link between consumption of omega 3 fatty acids and the delay or prevention of Alzheimer's disease, and potential positive effects on depression, arthritis, and the immune system. It is in the fattiest fish that we find the highest levels of omega 3 fatty acids, including salmon and sardines. Interestingly, raw fish has more fat than cooked fish, and thus more omega 3 fatty acids! One concern is that when fish is farmed (raised in a controlled environment) it frequently contains less fat and thus lower amounts of omega 3 fatty acids, and also may contain harmful chemicals - often antibiotics. Some sushi lovers request only wild-raised fish and avoid farmed fish. The thin sheets of seaweed, which are flattened, cut, and wrapped around maki and hand rolls, are rich in minerals. Iodine, essential for proper hormone function, is abundant in this dried sea vegetable, as are magnesium, calcium, iron, antioxidants, and folic acid. What are the health risks of eating sushi? •Sushi can be high in calories, although these calories are hidden in a number of ways. A simple tuna roll may have 200 calories, but if the chef includes mayonnaise, fried tempura pieces, or cream cheese, the additional fat may bring it to 500 calories. It's difficult to eat just one, and the calories mount. Both soy sauce and wasabi are low in calories, but can have astronomical amounts of salt. •Foodborne pathogens can hide in raw fish. Eating uncooked fish may expose us to bacteria, viruses and parasites. Roundworm, for example, is a threadlike parasite that can burrow into the stomach and cause painful symptoms. Some bacteria cause intestinal symptoms including nausea, vomiting, diarrhea and abdominal pain. Reputable chefs include fish that has been frozen, a process that kills bacteria and parasites, rendering these fish safe to consume. I should add that none of my family members, or for that matter anyone I know personally or professionally, has experienced any of these infections. Nonetheless, it is important to carefully choose where you eat your sushi. •The open waters of rivers, lakes and the sea expose fish to mercury, a known neurotoxin. When mercury gets into the water, it is converted into methylmercury and builds up in fish. Too much methylmercury in the human bloodstream can damage the developing nervous system in fetuses, infants, and young children. In adults, it can cause vision problems, memory loss, headaches and hair loss. Large predatory fish, including tuna, swordfish, marlin, and shark have the highest mercury levels. Fish that are lower in mercury include salmon, cod, cooked shellfish, canned light tuna, pollock, haddock, tilapia and catfish. Most adults needn't worry about a few meals per week containing these fish, though. According to the FDA, periodic consumption doesn't change the level of methylmercury in the body significantly. However, young children, pregnant women, nursing women, and women planning to get pregnant are advised to minimize their consumption. Interestingly, the USDA advises that the benefits of consuming these fish outweigh the risks. My suggestions for safe sushi consumption: •Leave sushi preparation to the experts. Don't make your own; that's when you run the highest risk of exposure to disease. •Make eating sushi a treat and not a staple. That will minimize your exposure to potentially harmful levels of mercury or disease pathogens. •Balance your sushi meal.Tofu is a good source of omega-3 fatty acids. Eat vegetables with your sushi. Enjoy fun, nutritious, and safe dining! Dr. Alan Frischer is former chief of staff and current chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.
********** Published: February 26, 2010 - Volume 8 - Issue 45