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.

There is strong scientific evidence from human trials that omega-3 fatty acids from fish or fish oil supplements (EPA + DHA) significantly reduce blood triglyceride levels. Benefits appear to be dose-dependent. 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.

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.

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.

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.

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.

Preliminary studies report reductions in angina associated with fish oil intake. Better research is necessary before a firm conclusion can be drawn.

Several studies in this area do not provide enough reliable evidence to form a clear conclusion, with some studies reporting no effects, and others finding benefits. Because most studies have been small without clear descriptions of design or results, the results cannot be considered conclusive.

Some research reports that regular intake of fish or fish oil supplements reduces the risk of developing atherosclerotic plaques in the arteries of the heart, while other research reports no effects. Additional evidence is necessary before a firm conclusion can be drawn in this area.

Several studies in this area do not provide enough reliable evidence to form a clear conclusion.

Several population (epidemiologic) studies report that dietary omega-3 fatty acids or fish oil may reduce the risk of developing breast, colon, or prostate cancer. Randomized controlled trials are necessary before a clear conclusion can be drawn.

There is promising evidence that omega-3 fatty acids may decrease the risk of cardiac arrhythmias. This is one proposed mechanism behind the reduced number of heart attacks in people who regularly ingest fish oil or EPA + DHA. Additional research is needed in this area specifically before a firm conclusion can be reached.

Omega-3 fatty acids are commonly taken by cancer patients. Although preliminary studies report that growth of colon cancer cells may be reduced by taking fish oil, effects on survival or remission have not been measured adequately.

It has been suggested that effects of omega-3 fatty acids on inflammation may be beneficial in patients with Crohn's disease when added to standard therapy, and several studies have been conducted in this area. Results are conflicting, and no clear conclusion can be drawn at this time.

A small amount of research in this area does not provide enough reliable evidence to form a clear conclusion.

Well-designed clinical trials are needed before omega-3 fatty acids can be recommended for the prevention of cognitive impairment or dementia.

Several studies on the use of omega 3 fatty acids in depression, including positive results in postpartum depression, do not provide enough reliable evidence to form a clear conclusion or replace standard treatments. However, based on one recent study, omega-3 fatty acids may have therapeutic benefits in childhood depression. Promising initial evidence requires confirmation with larger, well-designed trials.

There is preliminary evidence suggesting possible benefits of fish oil/omega-3 fatty acids in patients with dysmenorrhea. Additional research is necessary before a firm conclusion can be reached.

Several studies of EPA for eczema do not provide enough reliable evidence to form a clear conclusion.

There are conflicting results from several trials in this area.

Well-designed research is necessary before a clear conclusion can be reached.

There is not enough reliable evidence to form a clear conclusion in this area.

There is not enough reliable evidence to form a clear conclusion in this area.

Several studies of fish oil do not provide enough reliable evidence to form a clear conclusion in this area.

There is limited study of the use of fish oils in patients after undergoing coronary artery bypass grafting (CABG). Additional evidence is necessary before a firm conclusion can be drawn in this area.

Several randomized controlled trials have evaluated whether omega-3 fatty acid intake reduces blockage of arteries in the heart following balloon angioplasty (percutaneous transluminal coronary angioplasty/PTCA). The evidence in this area remains inconclusive.

Additional research is necessary before a conclusion can be drawn in this area.

Several studies in this area do not provide enough reliable evidence to form a clear conclusion.

There is promising preliminary evidence from several randomized controlled trials in this area. Additional research is necessary before a firm conclusion can be reached.

Several randomized controlled trials have examined the effects of alpha-linolenic acid in people with a history of heart attack. Although some studies suggest benefits, others do not. Additional research is necessary before a conclusion can be drawn in this area.

Several large studies of populations ("epidemiologic" studies) have examined the effects of omega-3 fatty acid intake on stroke risk. Some studies suggest benefits, while others do not. Effects are likely on ischemic or thrombotic stroke risk, and very large intakes of omega-3 fatty acids ("Eskimo" amounts) may actually increase the risk of hemorrhagic (bleeding) stroke. At this time, it is unclear if there are benefits in people with or without a history of stroke, or if effects of fish oil are comparable to other treatment strategies.

It has been suggested that effects of omega-3 fatty acids on inflammation may be beneficial in patients with ulcerative colitis when added to standard therapy, and several studies have been conducted in this area. Better research is necessary before a clear conclusion can be drawn.

There is preliminary evidence that fish oil supplementation does not improve appetite or prevent weight loss in cancer patients. Further study is warranted.

The available scientific evidence suggests that there are no significant long-term effects of fish oil in patients with diabetes. Most studies in this area are not well designed.

Although fish oil is able to reduce triglycerides, beneficial effects on blood cholesterol levels have not been demonstrated. Fish oil supplements appear to cause small improvements in high-density lipoprotein ("good cholesterol"); however, increases (worsening) in low-density lipoprotein levels ("bad cholesterol") are also observed. Fish oil does not appear to affect C-reactive protein (CRP) levels.

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 (glomerular filtration rate, serum creatinine), and less hypertension (high blood pressure) compared to patients not taking fish oil. However, several recent studies report no benefits on kidney function, and no changes have been found in rates of rejection or graft survival.