The truth about sushi

Once popular only in Asia, sushi is now a favourite across the world. After all, fish is healthful! Or is it? These tips will help you separate fact from fiction when it comes to consuming sushi.

Maybe. If you eat sushi no more than once a week, you should be fine, especially if you avoid bluefin tuna. Worried about the mercury in your seafood? Overall, experts say the benefits of eating fish far outweigh the risks (except for pregnant women and young children) if you avoid the fish highest in contaminants. The trouble is, many of the prized cuts used in sushi come from long-living, larger fish that are ocean predators, such as tuna, king mackerel, swordfish, tilefish and shark — exactly the ones that contain the most contaminants.

Food safety officials as well as sushi chefs often have little clue how much mercury is in the fish on your plate, as levels can vary greatly even among identical fish in the same catch. One thing is clear, however: research has shown that a great deal of sushi contains more mercury than experts previously thought — and more than is allowed by law.

In 2007, Oceana, a marine conservation organization based in Washington, DC, tested sushi samples from 23 cities in the United States. They found that a third of all tuna samples had higher mercury levels than the Food and Drug Administration (FDA) allows, and half of the samples were pretty close to the bar. Soon after the survey surfaced, The New York Times had labs test sushi samples from 20 restaurants and stores in Manhattan. They found that five of the establishments — or 25 percent — were selling fish that had unacceptably high mercury levels, with bluefin tuna topping the charts. That's no doubt why some environmental groups advise that no one eat bluefin tuna.

Eating just six pieces per week of the sushi the Times tested would put a diner's mercury intake over the FDA's safe threshold. Yet experts noted that these levels would probably cause problems only after months of regular consumption.Yellowfin tuna is a bit lower in mercury than bluefin, according to the Oceana test findings, and will usually be your most prudent tuna option at the sushi bar — but it still contains far more mercury than freshwater fish such as salmon. Of all fish, according to Oceana's report, your lowest-mercury choices include salmon, shrimp, cod, pollock, tilapia, scallops and mackerel (but not king mackerel).

Yes, but it's rare. The flesh of raw or undercooked freshwater fish such as mackerel, herring, cod, trout, striped bass, carp, pike and freshwater eel can have worms that can survive in your gastrointestinal tract — if they manage to get there alive. (Saltwater fish are less likely to carry parasites, although saltwater salmon can be iffy since it spawns in fresh water. Never order your salmon fillet "rare" at a restaurant.)

While they're nauseating to contemplate, the parasites that people sometimes get from eating contaminated sushi rarely cause fatal conditions.