evidence
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:
The effectiveness ratings for FISH OIL are as follows:
Effective for...
- 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. Fish oil supplements also appear to cause small improvements in high-density lipoprotein ("good cholesterol"); however, increases (worsening) in low-density lipoprotein levels (LDL/"bad cholesterol") are also observed. It is not clear if alpha-linolenic acid significantly affects triglyceride levels, and there is conflicting evidence in this area. The American Heart Association has published recommendations for EPA + DHA. Because of the risk of bleeding from omega-3 fatty acids, a qualified healthcare provider should be consulted prior to starting treatment with supplements. There is growing evidence that reducing C-Reactive Protein (CRP) is beneficial towards favorable cardiovascular outcomes, although additional research is pending in this area. The data on fish oils and CRP levels is mixed.
- High blood pressure. Multiple human trials report small reductions in blood pressure with intake of omega-3 fatty acid. DHA may have greater benefits than EPA. However, high intakes of omega-3 fatty acids per day may be necessary to obtain clinically relevant effects, and at this dose level, there is an increased risk of bleeding. Therefore, a qualified healthcare provider should be consulted prior to starting treatment with supplements. A meta-analysis of several studies revealed changes in blood pressure with the use of fish oil.17,18 The benefits tended to occur in older populations (>45 years) and generally required higher doses. Although the blood pressure changes were minor, they may nonetheless be clinically significant since even small changes in blood pressure can influence mortality rates from CHD and stroke. It is likely that the positive effects of fish oil on blood pressure are the result of an improvement in endothelial function.
- Secondary cardiovascular disease prevention (fish oil / EPA plus DHA). Several well-conducted randomized controlled trials report that in people with a history of heart attack, regular consumption of oily fish or fish oil/omega-3 supplements reduces the risk of non-fatal heart attack, fatal heart attack, sudden death, and all-cause mortality (death due to any cause). Most patients in these studies were also using conventional heart drugs, suggesting that the benefits of fish oils may add to the effects of other therapies.
- Sudden cardiac death. Strong evidence for the cardioprotective mechanism of omega-3 FAs at the lower doses achievable by fish ingestion relates to effects on fatal cardiac events rather than a general reduction in all cardiac events. For example, in the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto (GISSI) Miocardico Prevenzione trial there was no decrease in cardiac events overall, but those given EPA+DHA were at lower risk for fatal myocardial infarctions. Therefore, a reduction in SCD is most likely to be effected by an increased intake of omega-3 FAs at lower doses. In animal models, all three omega-3s—ALA, EPA, and DHA—have been shown to be equally capable of inhibiting the accumulation of high concentrations of cytosolic-free calcium in cardiac myoctes and stabilizing the electrical activity of the cell, potentially being the means of reduction of sudden death seen in the GISSI trial.
- Thrombosis, atherosclerosis, inflammation. Numerous effects of omega-3 FAs on thrombosis, atherosclerosis, and inflammation have been reported. These benefits require the higher doses of EPA afforded by highly concentrated high-EPA omega-3 supplements.
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.” Several large studies of populations ("epidemiologic" studies) report a significantly lower rate of death from heart disease in men and women who regularly eat fish. Other epidemiologic research reports no such benefits. It is not clear if reported benefits only occur in certain groups of people, such as those at risk of developing heart disease. Overall, the evidence suggests benefits of regular consumption of fish oil. However, well-designed randomized controlled trials which classify people by their risk of developing heart disease are necessary before a firm conclusion can be drawn.
- Protection from cyclosporine toxicity in organ transplant patients. There are multiple studies of heart transplant and kidney transplant patients taking cyclosporine (Neoral®), who were administered fish oil supplements. The majority of trials report improvements in kidney function, and less high blood pressure compared to patients not taking fish oil. Although several recent studies report no benefits on kidney function, the weight of scientific evidence favors the beneficial effects of fish oil.
- Rheumatoid arthritis (fish oil). Multiple randomized controlled trials report improvements in morning stiffness and joint tenderness with the regular intake of fish oil supplements for up to three months. Benefits have been reported as additive with anti-inflammatory medications such as NSAIDs (like ibuprofen or aspirin). However, because of weaknesses in study designs and reporting, better research is necessary before a strong favorable recommendation can be made. Effects beyond three months of treatment have not been well evaluated.
Possibly effective for...
- 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.
- Recurrent miscarriage in pregnant women with antiphospholipid syndrome. Taking fish oil seems to prevent miscarriage and increase live birth rate in pregnant women with a condition called antiphospholipid syndrome.
- High blood pressure and kidney problems after heart transplant. Taking fish oil seems to preserve kidney function and reduce the long-term continuous rise in blood pressure after heart transplantation.
- Damage to the kidneys and high blood pressure caused by taking a drug called cyclosporine. Cyclosporine is a medication that reduces the chance of organ rejection after an organ transplant. Fish oil might help reduce some of the unwanted side effects of treatment with this drug.
- Movement disorder in children (dyspraxia). Taking fish oil orally, in combination with evening primrose oil, thyme oil, and vitamin E (Efalex, Efamol Ltd), seems to improve movement disorders in children with dyspraxia.
- Developmental coordination disorder. A combination of fish oil (80%) and evening primrose oil (20%) seems to improve reading, spelling, and behavior when given to children age 5-12 years with developmental coordination disorder. However, it doesn’t seem to improve motor skills.
- Preventing blockage of grafts used in kidney dialysis. Taking fish oil orally seems to help prevent clot formation in hemodialysis grafts.
- Psoriasis. There is some evidence that administering fish oil intravenously (by IV) can decrease severe psoriasis symptoms. But taking fish oil by mouth doesn’t seem to have any effect on psoriasis.
- High cholesterol. There is interest in using fish oil in combination with “statin” drugs for some people with high cholesterol. Doctors were worried at first that taking fish oil might interfere with statin treatment, but early studies show this is not a problem, at least with the statin called simvastatin. Scientists think fish oil may lower cholesterol by keeping it from being absorbed in the intestine. There is some evidence that using vitamin B12 along with fish oil might boost their ability to lower cholesterol.
- Coronary artery bypass surgery. Taking fish oil seems to prevent coronary artery bypass grafts from re-closing following coronary artery bypass surgery.
- Cancer-related weight loss. Taking a high dose (7.5 grams per day) of fish oil seems to slow weight loss in some cancer patients. Some researchers believe these patients eat more because the fish oil is fighting depression and improving their mood.
- Asthma. Some research suggests fish oil may lower the occurrence of asthma in infants and children when taken by women late in pregnancy. Furthermore, fish oil seems to improve airflow, reduce cough, and lower the need for medications in some children with asthma. However, fish oil treatment doesn’t seem to provide the same benefit for adults.
Possibly ineffective for...
- Gum infection (gingivitis).
- Liver disease.
- Leg pain due to blood flow problems (claudication).
- Preventing migraine headaches.
- Preventing muscle soreness caused by physical exercise.
- Breast pain.
- Skin rashes caused by allergic reactions.
- Stomach ulcers.
Likely ineffective for...
- Type 2 diabetes. Taking fish oil doesn’t seem to lower blood sugar in people with type 2 diabetes. However, fish oil can provide some other benefits for people with diabetes, such as lowering blood fats called triglycerides.
Insufficient evidence to rate effectiveness for...
- Allergies. Some research suggests that mothers who take fish oil supplements during the late stages of pregnancy may lower the occurrence of allergies in their children.
- Alzheimer’s disease. There is some preliminary evidence that fish oil may help prevent Alzheimer‘s disease. But it doesn’t seem to help prevent a decline in thinking skills for most people who already have mild-to-moderate Alzheimer’s disease.
- Atopic dermatitis. Mothers who take fish oil supplements during pregnancy might reduce the occurrence and severity of atopic dermatitis in babies and children who are at risk for this condition. But fish oil doesn’t seem to be effective for treating atopic dermatitis.
- Atrial fibrillation. Research studies into the effects of fish oil on atrial fibrillation have produced conflicting results.
- Depression. There is inconsistent information about the effect of taking fish oil on depression. Some research shows that taking fish oil along with an antidepressant might help improve symptoms. But other research shows that taking fish oil does not improve symptoms.
- Dry eye syndrome. Some research links eating more fish with a lower risk of getting dry eye syndrome in women. Some preliminary clinical research also suggests that taking a specific product containing fish oil plus flaxseed oil (TheraTears Nutrition) might reduce symptoms of dry eye and increase tear production.
- Cancer. Research studies into the effects of fish oil on cancer prevention have produced conflicting results.
- Cataracts. There is some evidence that eating fish three times a week can modestly lower the risk of developing cataracts.
- Chronic fatigue syndrome (CFS). There is some conflicting evidence about the use of a product (Efamol Marine) that combines fish oil and evening primrose oil to reduce the symptoms CFS.
- Chronic kidney disease. Preliminary evidence shows that fish oil might have benefit for some people with chronic kidney disease who are receiving dialysis treatments.
- Thinking skills (cognitive function). Research studies into the effects of fish oil on cognitive function have produced conflicting results.
- Crohn’s disease. Research studies into the effects of fish oil on Crohn’s disease have produced conflicting results.
- Prediabetes. Early studies suggest that fish oil may help prevent prediabetes from advancing to type 2 diabetes.
- Infant development. There is some evidence that mothers who take 4 grams of fish oil daily during the last half of pregnancy may improve their baby’s cognitive development by some measures, but not others. At age 2.5 years, these children seem to have better hand and eye coordination, but reasoning, social, motor, and speech skills are not significantly improved.
- Ulcerative colitis. Research studies into the effects of fish oil on ulcerative colitis have produced conflicting results.
- Pregnancy complications. There is some evidence that taking fish oil during the last ten weeks of pregnancy can help prevent premature delivery. However, fish oil doesn’t seem to help prevent high blood pressure during pregnancy.
- Prematurity. Baby formula that has been fortified with fatty acids from fish oil and borage seems to improve growth and the development of the nervous system in premature infants, especially boys.
- Salicylate intolerance. Some limited research suggests that taking fish oil might improve symptoms of salicylate intolerance such as asthma attacks and itching.
- Schizophrenia. There is one report of fish oil improving schizophrenia in a pregnant woman.
- Systemic lupus erythematosus (SLE). Research shows conflicting results. Some studies suggest that fish oil helps the symptoms of SLE, while others show no effect.
- Irregular heartbeat affecting the ventricles (ventricular arrhythmias). Research studies into the effect of fish oil on ventricular arrhythmias have produced conflicting results.
- Improving night vision in children with a disorder called dyslexia. Children with dyslexia who take fish oil seem to be significantly better able to adapt to the dark.
Other conditions.
More evidence is needed to rate fish oil for these uses.
Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Acute myocardial infarction (heart attack), acute respiratory distress syndrome (ARDS), age related macular degeneration, aggressive behavior, agoraphobia, AIDS, allergies, Alzheimer's disease, anticoagulation, antiphospholipid syndrome, attention deficit hyperactivity disorder (ADHD), anthracycline-induced cardiac toxicity, bacterial infections, psychological disorders (borderline personality disorder), breast cysts, breast tenderness, chronic fatigue syndrome (postviral fatigue syndrome), chronic obstructive pulmonary disease, cirrhosis, common cold, congestive heart failure, critical illness, deficiency (omega-3 fatty acid), dermatomyositis, diabetic nephropathy, diabetic neuropathy, dyslexia, dyspraxia, endocrine disorders (glycogen storage diseases), exercise performance enhancement, fibromyalgia, gallstones, gingivitis, glaucoma, glomerulonephritis, gout, hay fever, headache, hepatorenal syndrome, hypoxia, ichthyosis (skin disorder), immunosuppression, inflammatory conditions (Behcet's syndrome), joint problems (cartilage repair), kidney disease prevention, kidney stones, leprosy, leukemia, malaria, male infertility, mastalgia (breast pain), memory enhancement, menopausal symptoms, menstrual cramps, methotrexate toxicity, multiple sclerosis, myopathy, nephritis (autoimmune), neuropathy, night vision enhancement, obesity, osteoarthritis, osteoporosis, otitis media (ear infection), panic disorder, peripheral vascular disease, pregnancy nutritional supplement, premature birth prevention, premenstrual syndrome, prostate cancer prevention, protection from isotretinoin drug toxicity, Raynaud's phenomenon, Refsum's syndrome, retinitis pigmentosa, Reye's syndrome, seizure disorder, Sjogren's syndrome, suicide prevention, tardive dyskinesia, tennis elbow, urolithiasis (bladder stones), vision enhancement, weight loss.
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