What is Fish oil?
Fish oil can be obtained from eating fish or by taking supplements. Fish that are especially rich in the beneficial oils known as omega-3 fatty acids include mackerel, tuna, salmon, sturgeon, mullet, bluefish, anchovy, sardines, herring, trout, and menhaden. They provide about 1 gram of omega-3 fatty acids in about 3.5 ounces of fish.
Fish oil supplements are usually made from mackerel, herring, tuna, halibut, salmon, cod liver, whale blubber, or seal blubber. Fish oil supplements often contain small amounts of vitamin E to prevent spoilage. They might also be combined with calcium, iron, or vitamins A, B1, B2, B3, C, or D.
What is the function of fish oil?
Fish oil is used for a wide range of conditions. It is most often used for conditions related to the heart and blood system. Some people use fish oil to lower blood pressure or triglyceride levels (fats related to cholesterol). Fish oil has also been tried for preventing heart disease or stroke. The scientific evidence suggests that fish oil really does lower high triglycerides, and it also seems to help prevent heart disease and stroke when taken in the recommended amounts. Ironically, taking too much fish oil can actually increase the risk of stroke.
Fish may have earned its reputation as “brain food” because some people eat fish to help with depression, psychosis, attention deficit-hyperactivity disorder (ADHD), Alzheimer’s disease, and other thinking disorders.
Some people use fish oil for dry eyes, glaucoma, and age-related macular degeneration (AMD), a very common condition in older people that can lead to serious sight problems.
Women sometimes take fish oil to prevent painful periods; breast pain; and complications associated with pregnancy such as miscarriage, high blood pressure late in pregnancy, and early delivery.
Fish oil is also used for diabetes, asthma, developmental coordination disorders, movement disorders, dyslexia, obesity, kidney disease, weak bones (osteoporosis), certain diseases related to pain and swelling such as psoriasis, and preventing weight loss caused by some cancer drugs.
Fish oil is sometimes used after heart transplant surgery to prevent high blood pressure and kidney damage that can be caused by the surgery itself or by drugs used to reduce the chances that the body will reject the new heart. Fish oil is sometimes used after coronary artery bypass surgery. It seems to help keep the blood vessel that has been rerouted from closing up.
When fish oil is obtained by eating fish, the way the fish is prepared seems to make a difference. Eating broiled or baked fish appears to reduce the risk of heart disease, but eating fried fish or fish sandwiches not only cancels out the benefits of fish oil, but may actually increase heart disease risk.
Two of the most important omega-3 fatty acids contained in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). See separate listings for EPA and DHA.
How effective is it?Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings for FISH OIL are as follows:
High triglycerides. High triglycerides are associated with heart disease and untreated diabetes. To reduce the risk of heart disease, doctors believe it is important to keep triglycerides below a certain level. Doctors usually recommend increasing physical activity and restricting dietary fat to lower triglycerides. Sometimes they also prescribe drugs such as gemfibrozil (Lopid) for use in addition to these lifestyle changes. Now researchers believe that fish oil, though not as effective as gemfibrozil, can reduce triglyceride levels by 20% to 50%. One particular fish oil supplement called Lovaza has been approved by the FDA to lower triglycerides. Lovaza contains 465 milligrams of EP and 375 milligrams of DHA in 1-gram capsules.
Likely effective for…
Heart disease. Fish oil may be effective in keeping people with healthy hearts free of heart disease. People who already have heart disease may be able to lower their risk of dying from heart disease by taking fish oil. Though not all researchers agree, some investigators believe that fish oil may be even more effective in reducing death from heart attacks than a group of commonly used cholesterol-lowering drugs called “statins.”
Possibly effective for…
High blood pressure. Fish oil seems to produce modest reductions in blood pressure in people with high blood pressure. The omega-3 fatty acids in fish oil seem to be able to expand blood vessels, and this brings blood pressure down.
Rheumatoid arthritis. Fish oil alone, or in combination with the drug naproxen (Naprosyn), seems to help people with rheumatoid arthritis get over morning stiffness faster. People who take fish oil can sometimes reduce their use of pain medications such as nonsteroidal anti-inflammatory drugs (NSAIDs).
Menstrual pain (dysmenorrhea). Taking fish oil alone or in combination with vitamin B12 seems to improve painful periods and reduce the need for pain medications such as nonsteroidal anti-inflammatory drugs (NSAIDS).
Attention deficit-hyperactivity disorder (ADHD) in children. Taking fish oil seems to improve thinking skills and behavior in 8 to 12 year-old children with ADHD.
Raynaud’s syndrome. There’s some evidence that taking fish oil can improve cold tolerance in some people with the usual form of Raynaud’s syndrome. But people with Raynaud’s syndrome caused by a condition called progressive systemic sclerosis don’t seem to benefit from fish oil supplements.
Stroke. Moderate fish consumption (once or twice a week) seems to lower the risk of having a stroke by as much as 27%. However, eating fish doesn’t lower stroke risk in people who are already taking aspirin for prevention. On the other hand, very high fish consumption (more than 46 grams of fish per day) seems to increase stroke risk, perhaps even double it.
Weak bones (osteoporosis). Taking fish oil alone or in combination with calcium and evening primrose oil seems to slow bone loss rate and increase bone density at the thigh bone (femur) and spine in elderly people with osteoporosis.
Hardening of the arteries (atherosclerosis). Fish oil seems to slow or slightly reverse the progress of atherosclerosis in the arteries serving the heart (coronary arteries), but not in the arteries that bring blood up the neck to the head (carotid arteries).
Kidney problems. Long-term use (two years) of fish oil 4-8 grams daily can slow the loss of kidney function in high-risk patients with a kidney disease called IgA nephropathy. Fish oil also seems to reduce the amount of protein in the urine of people who have kidney disease as a result of diabetes.
Bipolar disorder. Taking fish oil with the usual treatments for bipolar disorder seems to improve symptoms of depression and increase the length of time between episodes of depression. But fish oil doesn’t seem to improve manic symptoms in people with bipolar disorder.
Psychosis. Taking a fish oil supplement might help prevent full psychotic illness from developing in people with mild symptoms. This has only been tested in teenagers and adults up to age 25.
Weight loss. Some evidence shows that eating fish improves weight loss and decreases blood sugar in overweight people and people with high blood pressure. Preliminary research also shows that taking a specific fish oil supplement 6 grams daily (Hi-DHA, NuMega), providing 260 mg DHA/gram and 60 mg EPA/gram, significantly decreases body fat when combined with exercise.
Endometrial cancer. There is some evidence that women who regularly eat about two servings of fatty fish per week have a reduced risk of developing endometrial cancer.
Age-related eye disease (age-related macular degeneration, AMD). There is some evidence that people who eat fish more than once per week have a lower risk of developing age-related macular degeneration.
Reducing the risk of blood vessel re-blockage after heart bypass surgery or “balloon” catheterization (balloon angioplasty). Fish oil appears to decrease the rate of re-blockage up to 26% when given for one month before the procedure and continued for one month thereafter. Apparently, taking fish oil before surgery is important. When taken for less than one month before angioplasty, fish oil doesn’t help protect the blood vessel against closing down.