- What other names is Fish Oil known by?
- What is Fish Oil?
- Is Fish Oil effective?
- How does Fish Oil work?
- Are there safety concerns?
- Are there any interactions with medications?
- Dosing considerations for Fish Oil.
Fish Oil Safety and Side Effects
Fish oil is safe for most people. It can cause side effects including belching, bad breath, heartburn, nausea, loose stools, rash, and nosebleeds. Taking fish oil supplements with meals or freezing them can often decrease these side effects. Some fish meats are contaminated with mercury and other industrial and environmental chemicals. Fish oil supplements typically do not contain these contaminants.
Taking fish oil supplements can increase levels of the "bad" LDL cholesterol in some people. You will need blood tests periodically to ensure LDL cholesterols do not become too high.
High doses of fish oil might keep blood from clotting and can INCREASE the chance of bleeding.
Do not take fish oil if:
- You have liver disease.
- You are allergic to fish or seafood.
- You have a condition called bipolar disorder.
- You have an implantable defibrillator (a surgically placed device to prevent irregular heartbeat).
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.
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).
There is some scientific evidence that fish oils might have other benefits for the heart. Fish oils seem to help to prevent a second heart attack if started within hours of the first attack and continued for a year. Fish oils might also lower blood pressure in some people who have high blood pressure.
Fish oils might also be helpful for rheumatoid arthritis. People with rheumatoid arthritis seem to be less stiff in the morning if they take fish oils.
There is also some evidence that fish oils can help prevent migraine headaches in some people.
However, fish oils do not help atherosclerosis or "hardening of the arteries." They also do not seem to help for some other conditions people use them for such as gum infections, lupus, kidney or liver disease, or leg pain due to blood flow problems.
There isn't enough information to know if fish oils are effective for the other conditions people use them for, including: asthma, cancer, lung disease, hay fever, cystic fibrosis and many more.
- High triglycerides. Research suggests that fish oil from supplements and food sources can reduce triglyceride levels. The effects of fish oil appear to be the greatest in people who have very high triglyceride levels. Additionally, how much fish oil is consumed appears seems to directly affect how much triglyceride levels are reduced. One particular fish oil supplement called Lovaza has been approved by the FDA to lower triglycerides. A one-gram capsule of Lovaza contains 465 milligrams of EP and 375 milligrams of DHA.
Likely Effective for...
- Heart disease. Research suggests that consuming fish oil by eating fish can be effective for keeping people with healthy hearts free of heart disease. People who already have heart disease might also be able to lower their risk of dying from heart disease by eating fish or taking a fish oil supplement. However, for people who already take heart medications such as a "statin," adding on fish oil might not offer any additional benefit.
Possibly Effective for...
- Preventing an eye disease called age-related macular degeneration (AMD). There is some evidence that eating fish more than one time per week lowers the risk of developing age-related macular degeneration.
- Preventing re-blockage of blood vessels after angioplasty, a procedure to open a closed blood vessel. Fish oil appears to decrease the rate of blood vessel re-blockage by up to 45% when given for at least 3 weeks before an angioplasty and continued for one month thereafter.
- Miscarriage in pregnant women with an autoimmune disorder called antiphospholipid syndrome. Taking fish oil seems to prevent miscarriages and increase live birth rates in pregnant women with antiphospholipid syndrome.
- Asthma. Some research shows that taking fish oil improves symptoms and lowers the need for medications in some, but not all, children with asthma. Other research shows that fish oil can lower the occurrence of asthma in infants and children when taken by women during pregnancy but not during breastfeeding. However, taking fish oil does not seem to improve asthma symptoms in adults.
- Hardening of the arteries (atherosclerosis). Fish oil seems to slow or slightly reverse the progress of atherosclerosis in arteries that bring blood to the heart (coronary arteries), but not in those that bring blood to the neck to the head (carotid arteries).
- Attention deficit-hyperactivity disorder (ADHD) in children. Early research shows that taking fish oil improves attention, mental function, and behavior in children 8-13 years-old with ADHD. Other research shows that taking a specific supplement containing fish oil and evening primrose oil (Eye Q, Novasel) improves mental function and behavior in children 7-12 years-old with ADHD.
- Bipolar disorder. Taking fish oil with conventional treatments for bipolar disorder seems to improve symptoms of depression and increase the length of time between episodes of depression. However, fish oil does not seem to improve manic symptoms in people with bipolar disorder.
- Cancer-related weight loss. Taking a high dose of fish oil seems to slow weight loss in some cancer patients. Low doses of fish oil don't seem to have this effect. Some researchers believe these patients eat more because the fish oil is fighting depression and improving their mood.
- Coronary artery bypass surgery. Taking fish oil seems to prevent coronary artery bypass grafts from re-closing following coronary artery bypass surgery.
- High blood pressure caused by the drug cyclosporine. Cyclosporine is a medication that reduces the chance of organ rejection after an organ transplant. Taking fish oil seems to prevent high blood pressure caused by this drug. .
- 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.
- Damage to the kidneys caused the drug cyclosporine. Taking fish oil seems to prevent kidney damage in people taking cyclosporine. Fish oil also seems to improve kidney function during the recovery phase following the rejection of a transplanted organ in people taking cyclosporine.
- Developmental coordination disorder (DCD). 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 does not seem to improve motor skills.
- Menstrual pain (dysmenorrhea). Research shows that taking fish oil, alone or with vitamin B12, can improve painful periods and reduce the need for pain medications in women with menstrual pain.
- Movement disorder in children (dyspraxia). Taking a fish oil product that also contains evening primrose oil, thyme oil, and vitamin E (Efalex, Efamol Ltd) seems to decrease movement disorders in children with dyspraxia.
- Endometrial cancer. There is some evidence that women who regularly eat about two servings of fatty fish weekly have a reduced risk of developing endometrial cancer.
- Heart failure. Research shows that a higher intake of fish oil from foods or supplements is linked with a reduced risk for heart failure.
- Heart transplant. Taking fish oil seems to preserve kidney function and reduce the long-term rise in blood pressure after heart transplantation.
- Preventing blockage of grafts used in kidney dialysis. Taking high doses of fish oil short-term seems to help prevent blood clot formation in hemodialysis grafts. Taking lower doses long-term does not seem to have this effect.
- Abnormal cholesterol caused by HIV/AIDS treatment. Some research suggests that taking fish oil reduces triglyceride levels in people with abnormal cholesterol levels caused by HIV/AIDS treatment. Taking fish oil might also reduce total cholesterol levels in these people, although results are inconsistent.
- High blood pressure. Fish oil seems to slightly lower blood pressure in people with moderate to very high blood pressure. Some types of fish oil might also reduce blood pressure in people with slightly high blood pressure, but results are inconsistent. Fish oil seems to add to the effects of some, but not all, blood pressure-lowering medications. However, it doesn't seem to reduce blood pressure in people with uncontrolled blood pressure who are already taking blood pressure-lowering medications.
- A certain kidney disease called IgA nephropathy. Some research shows that long-term use of fish oil can slow the loss of kidney function in high-risk patients with IgA nephropathy. Fish oil might have greater effects when taken at higher doses. Also, it might be most effective in people with IgA nephropathy who have higher levels of protein in the urine.
- Weight loss. Some evidence shows that eating fish improves weight loss and decreases blood sugar in people who are overweight with high blood pressure. Early research also shows that taking a specific fish oil supplement (Hi-DHA, NuMega) lowers body fat when combined with exercise. However, other evidence suggests that taking another specific fish oil supplement (Lovaza) does not lower body weight in overweight people.
- Weak bones (osteoporosis). Research suggests that taking fish oil alone or together with calcium and evening primrose oil seems to slow the rate of bone loss and increase bone density at the thigh bone (femur) and spine in elderly people with osteoporosis.
- Psoriasis. There is some evidence that administering fish oil intravenously (by IV) can decrease severe psoriasis symptoms. Also, applying fish oil to the skin also seems to improve some symptoms of psoriasis. However, taking fish oil by mouth does not seem to have any effect on psoriasis.
- Psychosis. Some research shows that taking a fish oil supplement might help prevent full psychotic illness from developing in teenagers and young adults with mild symptoms. These effects of fish oil have not been tested in older people.
- Raynaud's syndrome. There is some evidence that taking fish oil can improve cold tolerance in some people with the usual form of Raynaud's syndrome. However, people with Raynaud's syndrome caused by a condition called progressive systemic sclerosis do not seem to benefit from fish oil supplements.
- Abnormal cholesterol following a kidney transplant. Early research suggests that taking fish oil alone or together with cholesterol-lowering drugs can improve cholesterol levels in people with abnormal cholesterol levels after a kidney transplant.
- Rheumatoid arthritis (RA). Taking fish oil by mouth, alone or together with the drug naproxen (Naprosyn), seems to help improve symptoms of RA. People who take fish oil can sometimes reduce their use of pain medications. Also, administering fish oil intravenously (by IV) reduces swollen and tender joints in people with RA.
- Stroke. Moderate fish consumption (once or twice weekly) seems to lower the risk of having a stroke by as much as 27%. However, very high fish consumption (more than 46 grams of fish per day) seems to increase stroke risk, perhaps even double it. Eating fish does not lower stroke risk in people who are already taking aspirin for prevention.
Possibly Ineffective for...
- Chest pain (angina). Research suggests that taking fish oil supplements does not reduce the risk of death or improve heart health in people with chest pain. Some evidence even suggests that fish oil supplements might actually increase the risk of heart-related death in people with chest pain.
- Liver scarring (cirrhosis). Taking fish oil by mouth does not seem to improve kidney problems associated with liver scarring caused by advanced liver disease.
- Leg pain due to blood flow problems (claudication). Taking fish oil by mouth does not appear to improve walking distance in people with leg pain due to blow flow problems.
- Abnormal cholesterol caused by clozapine. Clozapine is a drug used to treat schizophrenia. Early evidence suggests that taking fish oil reduces triglyceride levels, but increases total cholesterol and low-density lipoprotein (LDL or "bad") cholesterol, in people with abnormal cholesterol levels due to taking clozapine.
- Gum infection (gingivitis). Taking fish oil does not seem to improve gingivitis.
- Helicobacter pylori (H. pylori) infection. Taking fish oil by mouth does not seem to improve H. pylori infections when compared to standard medications.
- HIV/AIDS. Some evidence shows that eating food bars containing fish oil does not increase CD4 cell counts in people with human immunodeficiency virus (HIV).
- Breast pain (mastalgia). Taking fish oil does not appear to reduce long-term breast pain.
- Migraine headaches. Taking fish oil by mouth does not appear to decrease the number or severity of migraine headaches.
- Osteoarthritis. Evidence suggests that taking fish oil along with glucosamine sulfate does not decrease osteoporosis symptoms compared to glucosamine sulfate alone.
- Pneumonia. Population research shows no relationship between fish consumption and the risk of developing pneumonia.
Likely Ineffective for...
- Diabetes. Taking fish oil does not 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. Early 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 early evidence that fish oil might help prevent Alzheimer's disease. However, it does not seem to help prevent a decline in thinking skills for most people who have already been diagnosed with Alzheimer's disease.
- Scaly, itchy skin (eczema). Evidence about the effects of fish oil on atopic dermatitis is inconsistent. Early research suggests that 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. Other research found that fish oil did not reduce the risk of atopic dermatitis in babies. Fish oil does not seem to be effective for treating atopic dermatitis.
- Abnormal heartbeat (atrial fibrillation). Research studies into the effects of fish oil on abnormal heartbeat have produced conflicting results. Some research suggests that eating fish regularly lowers the risk of abnormal heartbeat. Other research suggests it does not.
- Autism. Some early research suggests that taking fish oil might lower hyperactivity in children with autism. Other research suggests it does not.
- Cancer. Research on the effects of fish oil in preventing cancer has produced conflicting results.
- Cataracts. There is some evidence that eating fish three times weekly can slightly lower the risk of developing cataracts.
- Chronic fatigue syndrome (CFS). There is some conflicting evidence about the use of a specific product (Efamol Marine) that combines fish oil and evening primrose oil to reduce the symptoms CFS.
- Chronic kidney disease. Early evidence shows that fish oil might benefit some people with chronic kidney disease who are receiving dialysis treatments.
- Thinking skills (cognitive function). Research on the effects of fish oil on cognitive function has produced conflicting results.
- Crohn's disease. Research studies into the effects of fish oil on Crohn's disease have produced conflicting results. Some research shows that taking a specific fish oil product (Purepa, Tillotts Pharma) can reduce the relapse of Crohn's disease for people who have recovered. However, other research shows that fish oil does not have this effect.
- Cystic fibrosis. Early research suggests that taking fish oil by mouth can improve lung function in people with cystic fibrosis. However, administering fish oil intravenously (IV) does not have this effect.
- Dementia. Some research suggests that eating fish at least once per week reduces the risk of developing dementia. Other research suggests there is not a link between fish consumption and the risk of dementia.
- Depression. There is inconsistent evidence on the effect of taking fish oil for depression. Some research shows that taking fish oil along with an antidepressant might help improve symptoms in some people. Other research shows that taking fish oil does not improve depression symptoms.
- Kidney damage in people with diabetes (diabetic nephropathy). Evidence suggests that taking fish oil does not improve kidney function in people with diabetic nephropathy.
- Dry eye syndrome. Some research shows that eating more fish is linked with a lower risk of getting dry eye syndrome in women. Some early 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.
- Dyslexia. Taking fish oil seems to improve night vision in children with dyslexia.
- Abnormal cholesterol or fat levels in the blood (dyslipidemia). There is conflicting evidence about the effects of fish oil on cholesterol and fat levels in the blood. Some research shows that taking fish oil can lower triglyceride levels, low density lipoprotein (LDL or "bad") cholesterol, and increase high density lipoprotein (HDL or "good") cholesterol in people with abnormal cholesterol levels. However, other research shows that taking fish oil daily does not have this effect.
- Advanced kidney disease (end stage renal disease). Some evidence suggests that taking fish oil reduces markers of swelling (inflammation) in people with advanced kidney disease.
- Muscle soreness due to exercise. Early research shows that taking fish oil before and during physical exercise does not seem to prevent muscle soreness in the arm. However, other evidence suggests that taking fish oil seems to reduce soreness following leg exercises.
- Exercise performance. Some evidence suggests that taking fish oil can improve lung function in athletes. However, other evidence suggests that taking fish oil does not improve endurance, recovery, heart rate, or exercise duration.
- 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 eat fish or take fish oil supplements during pregnancy may improve some aspects of their baby's mental development. Taking fish oil during breast-feeding does not have this effect. However, feeding infants formula fortified with fish oil appears to improve some aspect of the baby's vision by the age of 2 months.
- Multiple sclerosis. Taking a specific fish oil product (MaxEPA) does not appear to improve the duration, frequency, or severity of relapses in patients with multiple sclerosis.
- Swelling of the pancreas (pancreatitis). Evidence suggests that feeding intravenously (IV) with nutrition that has been fortified with fish oil reduces the number of days of renal replacement therapy needed by people with severe inflammation of the pancreas.
- Phenylketonuria (PKU). Some evidence suggests that taking fish oil supplements improves motor skills, coordination, and vision in children with a rare genetic disorder called phenylketonuria.
- Pregnancy complications. There is some evidence that taking fish oil or eating seafood during pregnancy can help prevent premature delivery. However, fish oil does not seem to help prevent high blood pressure during pregnancy.
- Prematurity. Baby formula that has been fortified with fatty acids from fish oil and borage oil seems to improve growth and nervous system development 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 symptoms of schizophrenia in a pregnant woman.
- Sickle cell disease. Early research suggests that taking fish oil can reduce severe pain episodes in people with sickle cell disease.
- Systemic lupus erythematosus (SLE). Some studies suggest that fish oil helps improve symptoms of SLE, while other studies show no effect.
- Ulcerative colitis. Research studies into the effects of fish oil for treating ulcerative colitis show conflicting results.
- Irregular heartbeat affecting the ventricles (ventricular arrhythmias). Research studies into the effect of fish oil on ventricular arrhythmias have produced conflicting results.
- Other conditions.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Next: How does Fish Oil work?
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Tips to keep it under control.