Oil from fish contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); both are omega-3 fatty acids.
Note: Taking vitamin E with fish oil may protect the oil from undergoing potentially damaging oxidation in the body.
3,000 mg daily omega-3 fatty acids
Many double-blind trials have shown that fish oil containing EPA and DHA lowers triglycerides levels.
3 to 15 grams daily omega-3 fatty acids
EPA and DHA, the omega-3 fatty acids found in fish oil, have been repeatedly shown to lower blood pressure.
Up to 20 grams per day of fish oil after consultation with a doctor
Supplementing with fish oil may improve symptoms and decrease disease activity.
3 grams daily of EPA plus DHA
Fish oil has anti-inflammatory effect and may help reduce pain. Many trials have proven that omega-3 fatty acids in fish oil partially relieve symptoms of rheumatoid arthritis.
Consult a doctor
Fish oil has been shown to reduce chest pain and the need for nitroglycerin.
Consult a doctor
Research shows that fish oil partially reduces reactions to allergens that can trigger asthma attacks. It has also been shown in one study to prevent exercise-induced asthma attacks.
3 to 6 grams fish oil daily, containing at least 30% omega-3 fatty acids
Fish oil may reduce risk factors for atherosclerosis and heart disease. One trial showed that people who took fish oil had a slowing of the progression of their arterial plaque and had a decrease in cardiovascular events such as heart attack and stroke.
Daily omega-3 fatty acids: 9.6 grams for adults, 1,290 to 4,300 mg for children
People with depression may have lower blood levels of omega-3s. Taking fish oil, in addition to prescribed medication, improved symptoms in one study.
2.7 grams daily omega-3 fatty acids in enteric-coated capsules
Fish oil helps relieve the inflammation of the gut that occurs in people suffering from Crohn’s disease.
Where to Find It
EPA and DHA are found in mackerel, salmon, herring, sardines, sablefish (black cod), anchovies, albacore tuna, and wild game. Cod liver oil contains large amounts of EPA and DHA. Fish oil supplements typically contain 18% EPA and 12% DHA, though more purified (that is, higher in EPA and DHA) fish oil supplements are sometimes available. In addition, DHA is available in a supplement that does not contain significant amounts of EPA.
How to Use It
Presumably, healthy people who frequently eat fatty fish (several times per week) have no need to supplement with fish oil. How much EPA and DHA, if any, should be supplemented by healthy people who do not eat much fatty fish, remains unclear.
Most researchers studying the effects of EPA and DHA in people who have a variety of health conditions have given those people at least 3 grams of the total of EPA plus DHA—an amount that may require 10 grams of fish oil, because most fish oil contains only 18% EPA and 12% DHA.
The health benefits for people with Crohn’s disease have been reported with a special, enteric-coated preparation of purified EPA/DHA manufactured from fish oil. This preparation of purified fatty acids does not cause the gastrointestinal symptoms that often result from taking regular fish oil supplements, which makes it a preferable source of EPA/DHA for people with gastrointestinal illnesses.
In one trial, the maximum amount of fish oil tolerated by people being treated for cancer-related weight loss was reported to be approximately 21 grams per day. However, in people who do not have cancer, the maximum tolerated amount may be different.
So-called “primitive” diets have much higher levels of EPA and DHA than modern diets. As a result, some researchers and doctors believe that most people who eat a typical Western diet are likely to be consuming less-than-optimal amounts of EPA and DHA. To a very limited extent, omega-3 fatty acids from vegetable sources, such as flaxseed oil, can be converted in the body to EPA.
At least four studies have reported a reduced blood level of omega-3 fatty acids in people with depression.
People with rheumatoid arthritis have been found to have decreased levels of omega-3 fatty acids, such as are found in fish oil, in their joint fluid and blood.
While those with heart disease and diabetes have often been reported to benefit from supplementation with fish oil, both groups should check with their doctor before taking more than 3 grams of fish oil per day for several months.
Elevations in blood sugar and cholesterol levels may occur in some people who take fish oil. The increase in blood sugar appears to be related in part to the amount of fish oil used. The impairment of sugar metabolism sometimes caused by supplementation with fish oil has been prevented by the addition of half an hour of moderate exercise three times a week.
While supplementation with fish oil consistently lowers triglycerides, the effect of fish oil on LDL (“bad”) cholesterol varies, and in some people, fish oil supplementation has been reported to increase LDL levels.
Interactions with Supplements, Foods, & Other Compounds
People who took fish oil and who also took 15 grams of pectin per day were reported to have reductions in LDL cholesterol. This suggests that pectin may overcome the occasional problem of increased LDL cholesterol reported in people who supplement with fish oil. The LDL-cholesterol-raising effect of EPA and DHA has also been reported to be prevented by taking garlic supplements (or presumably including garlic in the diet) along with EPA and DHA.
Some evidence suggests that adding vitamin E to fish oil may prevent fish oil-induced increase in blood sugar levels.
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