One fish, two fish....
Over the years, media reports on whether to eat fish have flopped around like a trout out of water. But if you read enough studies, a pattern becomes clear: Eating fish seems to lower the risk of sudden death heart attacks ... and once a week may be enough.
"We need more data, but the evidence is compelling that having some fish in your diet is better than having no fish," says Christopher O'Donnell of the Framinghain Heart Study in Massachusetts.
The Beat Goes On
Nearly half a million Americans will die of a heart attack this year. That's about one every minute.
Roughly half will suffer a myocardial infarction--that is, some of the heart muscle (myocardium) will die because the coronary arteries that nourish the heart muscle get blocked, usually by a blood clot that gets stuck in an artery that's already clogged.
The other half will suffer sudden cardiac death--that is, they'll die within an hour after the heart attack begins. In most cases, the heart stops beating because the electrical impulses that control its rhythm go awry (arrhythmia). More than half of the victims have no history of heart disease.
"People collapse and die unexpectedly if they're not resuscitated," says David Siscovick of the University of Washington. "Even in Seattle, where the paramedics are some of the best in the world, eight out of ten people who go into cardiac arrest die. It's highly lethal."
Researchers know less about how to prevent this less-common but more-deadly kind of heart attack. The omega-3 fatty acids in fish oils offer a clue.
"In animals, we can prevent sudden death with these fatty acids," says Alexander Leaf of Massachusetts General Hospital in Boston. In monkeys, dogs, and rats, it's tougher to induce arrhythmia if the animals are fed diets rich in fish oil instead of other fats.
And in test tubes, says Leaf, "fish oils stabilize each cell in the heart so that it's electrically more resistant to abnormal stimuli that can set off an arrhythmia."
Once a Week
In people, the evidence is messier, perhaps because it's harder to measure how much fish--and what else--they eat. Among the key findings:
* The Physicians' Health Study followed more than 20,000 men for 11 years. Those who initially reported eating fish at least once a week were half as likely to die of sudden death over the next decade as those who ate it less than once a month.
* Siscovick interviewed 334 patients (or spouses of patients) who had suffered cardiac arrest in Seattle. Those who had been eating a fatty fish meal at least once a week had half the risk of cardiac arrest of those who had been eating none at all.
* In Wales, researchers randomly assigned male heart attack survivors to eat at least two weekly portions of fatty fish I like salmon, trout, mackerel, herring, or sardines or to follow other advice (to eat more fiber, for example). After two years, the fish-eaters had a 29 percent lower risk of dying.
But not all studies agree. One found a link with myocardial infarctions, but not sudden death. Others found no link at all--perhaps because they included few people who ate no fish. "We still have crude instruments for teasing out what foods and what types of fish people are eating," says O'Donnell.
The answer to the uncertainty, says Leaf, is a clinical trial. "We want to take patients who miraculously survive cardiac arrest an now have an imp an defibrillator," a device that corrects the heart's rhythm whenever it becomes irregular.
"We would randomly assign them to take either olive oil or fish oil and see if either can reduce the number of times the defibrillator has to fire." Until then, researchers have only imperfect evidence to go on.
Fish has less saturated fat than red meat or chicken. That alone is good reason to eat it at least once a week.
Of course, that's the fresh fish you buy and cook at home without cream sauce, butter, or cheese. Fish from restaurants could be chock full of saturated or trans fats that threaten your heart (see "Restaurant Roulette," p. 7).
Does your heart care which species you buy?
It's not clear. Fatty fish are richer in the omega-3 fatty acids--eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)--that seem to prevent arrhythmias in animals. In people, one study found a lower risk whether the fish was fatty or not.
Our advice: Go for at least some fatty fish, since its benefits are backed by stronger evidence. "If you have a choice and you like both, you're better off with the fatty fish," says William Harris of the University of Missouri in Kansas City. If lower-fat fish is the only kind you like, it's better than no fish at all.
What about vegetarians? Plants like flax and purslane have alpha-linolenic acid, a fatty acid that's similar to EPA and DHA. But it's not clear if it acts exactly like fish oils in the body.
Only one preliminary study has compared them. Researchers in India gave fish oil, mustard seed oil (a good source of alpha-linolenic acid), or a placebo to 360 people suspected of having had a heart attack, After one year, both groups of oil-takers had fewer arrythmias than the placebo group, but only the fish-oil-takers had a lower death rate.
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RELATED ARTICLE: RESTAURANT ROULETTE
Yes, seafood is healthy...when it's first caught, and (maybe) if you cook it at home. But seafood's fat and sodium numbers can climb sky-high when you're dining out, Fried seafood is even high in artery-clogging (saturated plus trans) fat.
Restaurant Seafood Calories Total Fat (g) Broiled or grilled scallops (6 oz.) 150 3 Broiled low-fat fish (cod, haddock, flounder, etc.) (6 oz.) 210 5 Subway 6" Tuna Sub, made with light mayo (9 oz.)(1) 380 15 Broiled salmon (8 oz.) 420 21 Fried fish (9 oz.) 520 24 Fried shrimp (7 oz.) 520 26 McDonald's Fish Filet Deluxe (8 oz.) 560 28 Tuna salad sandwich (11 oz.) 720 43 Fried seafood combo (14 oz.) 970 50 Tuna salad sandwich with mayo on the bread (11 oz.) 830 56 Restaurant Seafood Artery-Clogging Fat (g) Broiled or grilled scallops (6 oz.) 1 Broiled low-fat fish (cod, haddock, flounder, etc.) (6 oz.) 1 Subway 6" Tuna Sub, made with light mayo (9 oz.)(1) 2(*) Broiled salmon (8 oz.) 4 Fried fish (9 oz.) 8 Fried shrimp (7 oz.) 10 McDonald's Fish Filet Deluxe (8 oz.) 6(*) Tuna salad sandwich (11 oz.) 8(*) Fried seafood combo (14 oz.) 19 Tuna salad sandwich with mayo on the bread (11 oz.) 10(*) Restaurant Seafood Sodium (mg) Broiled or grilled scallops (6 oz.) 1,000 Broiled low-fat fish (cod, haddock, flounder, etc.) (6 oz.) 360 Subway 6" Tuna Sub, made with light mayo (9 oz.)(1) 930 Broiled salmon (8 oz.) 340 Fried fish (9 oz.) 840 Fried shrimp (7 oz.) 970 McDonald's Fish Filet Deluxe (8 oz.) 1,160 Tuna salad sandwich (11 oz.) 1,320 Fried seafood combo (14 oz.) 1,920 Tuna salad sandwich with mayo on the bread (11 oz.) 1,360
(1) = Numbers do not include optional cheese, oil, or mayo on bread
(*) = does not include trans fat.
Foods are ranked from least to most total fat. All numbers have been rounded.
Source: Company information and Nutrition Action Healthletter restaurant studies.
RELATED ARTICLE: FISHING FOR OMEGAS
Looking for fish oils to (maybe) cut your risk of a heart attack? No one knows exactly how much it takes. In some studies, the risk was lower in people who ate one serving of fatty fish (about 1.5 grams of omega-3 fats) a week,
In general, fattier fish are richer sources, but some--like farmed catfish--are relatively low in omega-3s. Farmed fish are higher in fat than their wild cousins (most of the extra fat is unsaturated, so it's not a real threat to your heart). More fat usually means an extra 30 to 80 calories a serving.
For most species, our serving size is six ounces of cooked fish because that's a typical portion served at seafood restaurants. To get that much, start with about eight ounces raw.
Omega-3 Fish Fat Fats(*) (6-oz. cooked, unless specified) (grams) (grams) Salmon, Atlantic, farmed 21# 3.7 Salmon, Atlantic, wild 14 3.1 Sardines, in sardine oil (3 oz.) 13 2.8 Salmon, coho, farmed 14# 2.2 Trout, rainbow, farmed 12# 2.0 Salmon, coho, wild 7 1.8 Herring, kippered (3 oz.) 11 1.8 Trout, rainbow, wild 10# 1.7 Swordfish 9 1.4 Sardines, in tomato sauce (3 oz) 10 1.4 Herring, pickled (3 oz.) 15 1.2 Oysters (3 oz., steamed) 4 1.1 Mackerel, canned (3 oz.) 5 1.0 Pollock 2 0.9 Flounder or Sole 3 0.9 Whiting 3 0.9 Rockfish 3 0.8 Halibut 5 0.8 Sardines, in vegetable oil (3 oz.) 10 0.8 Tuna, white, canned (3 oz) 3 0.7 Scallops 2 0.6 Perch, ocean 4 0.6 Cod, Pacific 1 0.5 Tuna, fresh 2 0.5 Crab, blue (3 oz., steamed) 2 0.4 Haddock 2 0.4 Catfish, wild 5 0.4 Fish sticks (6) 21# 0.4 Cod, Atlantic 1 0.3 Crab, Dungeness (3 oz, steamed) 1 0.3 Shrimp (3 oz., steamed) 1 0.3 Catfish, farmed 14# 0.3 Tuna, light, canned (3 oz.) 1 0.2 Clams (3 oz, steamed) 2 0.2 Crayfish, farmed (3 oz., steamed) 1 0.1 Lobster (3 oz, steamed) 1 0.1
# includes 3 to 5 grams of saturated fat (most other fish are lower).
(1) canned in water.
(*) Includes EPA and DHA only.
Sources: USDA and (for sardines in sardine oil) Amer. 1. Clin. Nutr, 66: 1029S, 1997.
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|Title Annotation:||includes related articles on fish in restaurants; fat in fish; eating fish to prevent heart attacks|
|Publication:||Nutrition Action Healthletter|
|Date:||Jun 1, 1998|
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