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Definition
Fish fits well in a healthy diet since it replaces red meat, which has a heavy load of saturated fat. But fish may go farther than that. A certain type of fat in fish oil (omega-3 fatty acids) may actually be good for the heart.
Researchers began to explore the possible cardiovascular benefits of fish oil some 20 years ago when they first noted that Greenland Eskimos rarely developed coronary heart disease.
Heredity does not account for this - Eskimos who migrate to other countries eventually assume the same coronary risk as their new compatriots. One study, for example, demonstrated that Eskimos who move to Denmark develop coronary disease at the same rate as Danes - more than 10 times the rate of Eskimos in Greenland.
Instead, the explanation appears to lie in the native diet: Eskimos typically consume just as much fat as Danes do, but in Greenland that fat comes entirely from the sea. In Denmark, on the other hand, dietary fat comes primarily from land animals, much as it does in the U.S.
Effects Of Fish Oil
If fish oil indeed lowers the risk of coronary disease among fish-eating people, how does it do it? Replacing saturated fat in the diet may provide part of the answer, but there seems to be more to it than that. Numerous experiments have shown that fish oil:
- Makes platelets less sticky, decreasing the risk of dangerous blood clots in narrowed arteries
- Lowers blood levels of triglycerides, fats that may help clog arteries with cholesterol and that appear to promote clotting
- Helps reduce blood pressure modestly in people with hypertension.
Researchers suspect that those effects help keep the arteries open and allow blood to flow more smoothly. In studies of laboratory animals fed a high-fat diet, fish oil has slowed the development of arterial deposits.
Research in humans has focused on coronary disease patients undergoing angioplasty, in which a tiny balloon is threaded through clogged arteries and inflated to clear plaque deposits.
Side Effects Of High Doses Of Omega-3
Most of the studies used eight to 20 capsules each day, supplying 3 to 10 grams of omega-3. (You would have to eat nearly two pounds of salmon to get 10 grams of omega-3).
But there are serious concerns about side effects:
- The decreased ability of the blood to clot has a negative effect. The same Eskimos who have a low incidence of heart disease have a high risk of hemorrhagic stroke, perhaps because of the decreased clotting ability of their blood. If you consume lots of fish oil, the anti-clotting effect may be dangerous in an accident or during surgery
- Large doses can cause nausea, diarrhea, belching, and a bad taste in the mouth
- Like all fats, omega-3 is a concentrated source of calories - some recommended doses supply 200 calories a day
- Fish oil in liquid or capsule form may contain pesticides or other contaminants, especially if made from fish livers.
- Cod liver oil is overly rich in vitamins A and D, which can be toxic in high doses
- Prolonged consumption of fish oil may result in a vitamin E deficiency (polyunsaturated fats increase your need for E). Some manufacturers have thus added this vitamin to their supplements.
- Recent studies suggest that large doses of fish oil may suppress certain aspects of the immune system.
Recommendations
Many experts recommend eating fish but not the routine use of fish oil supplements. The evidence to date argues against investing in fish oil supplements such as Cardi-Omega 3 and SuperEPA.
The side effects, such as diarrhea and upset stomach, are often severe. It is, moreover, unclear whether the supplements provide the same benefits as fish. Fish itself is one of the best foods available. Besides the oil, it is rich in protein and iron, B vitamins and other nutrients.
If you have rheumatoid arthritis or psoriasis, fish oil supplements may be worth a try, but consult your doctor first.
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