Nine Questions About America's
#1 Fish
For: Fish Can Do's, July 2002
Never have there been so many choices in canned tuna. You can even buy tuna in a vacuum-sealed pouch—so you needn't drain it or recycle the can. There's tuna in a jar: Portuguese ventresca (the tender belly of albacore tuna). Fresh tuna, which tastes like an entirely different fish, is also more widely available than ever. Here's what you need to know about tuna.
What kind of tuna is used in cans? Is "solid" better than "chunk"?
Albacore, firm and light-colored, is the most prized variety,
the only one that can be identified as "white" on the can. Bonito
albacore is a gourmet item. Skipjack, bluefin, and yellowfin tuna are
also popular, usually packaged as "chunk light" or "solid
light." Tongol may also be packaged as "chunk light"—it's
a small tuna from the waters of Thailand and the western Pacific with
very white flesh and a less fishy flavor than larger fish. Usually packed
in water, it's sold in health-food stores. "Solid" on a
label means larger pieces; "chunk," smaller. Choose whichever
you like best. Chunk is usually cheaper. Oil-packed chunk tuna absorbs
more of the oil than solid white.
What are omega-3s? Does tuna have any?
The fat in fish is rich in polyunsaturated fatty acids called omega-3s. These reduce blood clotting and may lower the risk of coronary artery disease and fatal heart attacks. They may even be beneficial against rheumatoid arthritis and psoriasis, and possibly reduce the risk of macular degeneration (a cause of blindness). There's no U.S. government recommendation for omega-3 intake, but you should include some in your diet (food is the best source, not pills). To get omega-3s, the American Heart Association advises eating at least two servings of fish weekly. Like fresh tuna, canned tuna (particularly albacore) is a good source of omega-3s. These fats are not listed on the label. One reason to choose tuna packed in water rather than oil is that you can drain the water without losing any omega-3s, but draining off the oil takes about one-fourth of the fish's omega-3s with it.
Is the "spring water" in which some tuna is packed really from a spring?
Chicken of the Sea says its cannery in Pago Pago (American
Samoa) taps directly into a natural spring. But since you throw away most
of the water—and the tuna is subjected to high heat during canning—it
doesn't matter where the water comes from.
What kind of tuna is most nutritious?
There's not a lot of difference from one species to another. Albacore does have slightly more omega-3s than other types. And water-packed is almost always lower in fat and calories than oil-packed, even when you drain off the oil.
What about fat and cholesterol in tuna?
Cholesterol isn't an issue with tuna. The fish contains 10 to 20 milligrams in 2 ounces—less than poultry. Fat content, including omega-3s, varies according to the fish, depending on what it ate, where it was caught, and water temperature. While water-packed solid white tuna generally has only 1 or 2 grams of fat per 2-ounce serving, occasionally cans of the leading brands supply 5 grams in 2 ounces, as much as drained oil-packed tuna. The varieties used for chunk light tuna are usually low in fat, supplying only 1/2 gram per 2-ounce serving. But all you have to do is read the label—fat content is always listed. If you're concerned about calories, it makes sense to choose the water-packed tuna lowest in fat. If you want more omega-3s, choose the higher-fat albacore.
What kind of tuna is oil-packed and what kind of oil is used?
Most surface tuna is canned in oil—soy, canola, or
olive—because these fish have a lower fat content and a drier texture.
Deepwater tuna, such as albacore, are smaller and have more fat, and they
are often packed in water.
What about sodium?
Canned fish, including tuna, is usually high in added sodium
(about 250 milligrams per 2-ounce serving). Another plus for water-packed
tuna: you can cut the sodium content by draining and rinsing the fish.
You can also buy low-sodium varieties.
What about mercury?
Mercury gets into the ocean via pollution—and it's
also there naturally. Nearly all fish contain a little mercury; large,
long-lived fish that feed on other fish have more. But this should not
be a worry with tuna—the levels are generally quite low. Pregnant
and nursing women (or those who might become pregnant) should be concerned
about mercury in fish, but tuna is not on the "don't eat"
list. (Tilefish, king mackerel, swordfish, and shark may contain enough
mercury to harm a fetus, so pregnant women should avoid them.) Still,
it's always a good idea to vary your fish intake, whether you are
pregnant or not. Don't eat the same type of fish every day.
What about dolphins?
Yellowfin tuna in the Eastern Tropical Pacific tend to swim
below schools of dolphins, and huge nets can encircle them all, resulting
in injury or death for the dolphins. Bumble Bee, Chicken of the Sea, and
StarKist are committed to a dolphin-safe policy: they won't buy tuna
caught with dolphins. Tuna sold fresh, by the way, are caught by other
means, such as long lines. The claim "dolphin safe" must be
verified by the National Marine Fisheries, which inspects the fishing
vessels. Some companies put the label on all their canned tuna, even albacore—which
don't swim with dolphins.
UC Berkeley Wellness Letter, September 2001
