A perennial favorite on sushi bar menus everywhere, but also a popular canned convenience food; tuna is one of the most consumed fishes on Earth. A large carnivorous fish that feeds in cold water, several varieties of tuna are available, including yellowfin, bluefin, and albacore.
Its raw flesh is deep red and firm, with a salty aroma reminiscent of beef. When cooked, the flesh turns grey, resembling beefsteak.
Famed for its omega 3 fatty acid content and rich, easily digestible protein, tuna also presents significant health risks. Because mercury bioaccumulates as moves up the food chain, and tuna eat lots of smaller fish mercury toxicity tops the list, as several recent studies show that most of the tuna on the market exceeds US and Japanese government standards for mercury levels.
Most of the tuna consumed in Japan is eaten raw, and as sushi gains popularity elsewhere, more and more people enjoy it this way. Tuna sashimi, or raw fish fillets, is one of the most easily digestible proteins available. The quality must be outstanding, though, or you may run into problems with parasites or possible food poisoning.
What to Look for
Quality tuna sashimi is naturally deep, dark red, and almost translucent. As it ages, it becomes more cloudy and pink, and may be dyed to disguise its age. The prominence of fishy odor increases as it ages as well. Fresh fish will smell slightly sweet and salty but with only a hint of fish on the nose. Keep in mind that a bargain at the fish counter may be a catch that?s a bit over the hill.
In choosing canned tuna, look for dolphin-friendly labels to help support our finned mammalian friends, and watch out for cheaply made brands or damaged cans, a potential source of food poisoning or just plain bad-tasting tuna.
When buying fish, much more so than other commodities, you get what you pay for. You may find a deal, but odds are, you'll end up with something "fishy."
Common Pitfalls
Because of its hefty mercury content, pregnant women or those who are seeking enhanced fertility should not consume tuna, swordfish, yellowtail, shark or sea bass at all. These are species with the highest known mercury levels. The rest of us should not consume tuna more than a few times a month. Mercury causes neurological damage, impairs the immune system and slows and degrades metabolism and reproduction. Worse, once mercury enters the body, it?s excreted very slowly, causing buildup over time, which is how the tuna ended up with such high levels in the first place.
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