An animal study involving the omega-3 ETA discovered that subjects experienced a drop in overall inflammation similar to that caused by NSAIDs (non-steroidal anti-inflammatory drugs), but without the dangerous gastrointestinal side effects. The study authors also pointed out that eicosapentaenoic acid seems to be even more potent than the conventional omega-3s found in fish oil supplements (EPA/DHA). (56)

Heavy metal poisoning by the body's accumulation of traces of heavy metals, in particular mercury, lead, nickel, arsenic, and cadmium, is a possible risk from consuming fish oil supplements.[medical citation needed] Also, other contaminants (PCBs, furans, dioxins, and PBDEs) might be found, especially in less-refined fish oil supplements.[citation needed] However, heavy metal toxicity from consuming fish oil supplements is highly unlikely, because heavy metals selectively bind with protein in the fish flesh rather than accumulate in the oil. An independent test in 2005 of 44 fish oils on the US market found all of the products passed safety standards for potential contaminants.[107][unreliable source?]
Most Americans take in far more of another essential fat—omega-6 fats—than they do omega-3 fats. Some experts have raised the hypothesis that this higher intake of omega-6 fats could pose problems, cardiovascular and otherwise, but this has not been supported by evidence in humans. (4) In the Health Professionals Follow-up Study, for example, the ratio of omega-6 to omega-3 fats wasn’t linked with risk of heart disease because both of these were beneficial. (5) Many other studies and trials in humans also support cardiovascular benefits of omega-6 fats. Although there is no question that many Americans could benefit from increasing their intake of omega-3 fats, there is evidence that omega-6 fats also positively influence cardiovascular risk factors and reduce heart disease.
Egert, S., Somoza, V., Kannenberg, F., Fobker, M., Krome, K., Erbersdobler, H. F., and Wahrburg, U. Influence of three rapeseed oil-rich diets, fortified with alpha-linolenic acid, eicosapentaenoic acid or docosahexaenoic acid on the composition and oxidizability of low-density lipoproteins: results of a controlled study in healthy volunteers. Eur J Clin Nutr 2007;61(3):314-325. View abstract.
Higher visual acuity after DHA supplementation is a consistent finding in infants born preterm. For infants born at term, the results are less consistent and are better explained by differences in sensitivity of the visual acuity test (electrophysiologic tests being more sensitive than subjective tests) or by differences in the amount of DHA included in the experimental formula.

Recent studies have shown that the consumption of fish oil (or, more specifically, the omega-3 fatty acids found in fish oil) can improve fertility in both men and women. DHA, which is a byproduct of omega-3 fatty acids, plays a key role in the mobility of sperm and health of sperm in men. Low blood levels of DHA have been linked to decreased fertility. Animal studies have found that the DHA in fish is vital to changing dysfunctional round-headed sperm into strong swimmers with cone-shaped heads packed with egg-opening proteins. (29)
Dornstauder, B., Suh, M., Kuny, S., Gaillard, F., MacDonald, I., Michael T. Clandinin, M. T., & Sauvé, Y. (2012, June). Dietary docosahexaenoic acid supplementation prevents age-related functional losses and A2E accumulation in the retina. Investigative Ophthalmology and Visual Science. Retrieved from
Due to the anticipated heterogeneity, a random-effects meta-analysis was chosen rather than a fixed-effects meta-analysis because random-effects modeling is more stringent and incorporates an among-study variance in the calculations. The entire meta-analysis procedure was performed on the platform of Comprehensive Meta-analysis statistical software, version 3 (Biostat). Under the preliminary assumption that the scales for anxiety symptoms are heterogeneous among the recruited studies, we chose Hedges g and 95% confidence intervals to combine the effect sizes, in accordance with the manual of the Comprehensive Meta-analysis statistical software, version 3. Regarding the interpretation of effect sizes, we defined Hedges g values 0 or higher as a better association of treatment with reduced anxiety symptoms of omega-3 PUFAs than in controls. For each analysis, a 2-tailed P value less than .05 was considered to indicate statistical significance. When more than 1 anxiety scale was used in a study, we chose the one with the most informative data (ie, mean and standard deviation [SD] before and after treatment). We entered the primary outcome provided in the included articles or obtained from the original authors. As for the variance imputation, we mainly chose the mean and SD before and after treatment. Later, we entered the mean and SD and calculated the effect sizes based on the software option, standardized by post score SD. In the case of studies with 2 active treatment arms, we merged the 2 active treatment arms into 1 group. If these 2 active treatment arms belonged to different subgroups (ie, different PUFA dosage subgroups), we kept them separate. Regarding the numbers of participants counted, we chose intention-to-treat as our priority. If there were insufficient data in the intention to treat group (ie, some studies only provided the changes in anxiety severity in those participants completing trials), we chose instead the per-protocol numbers of participants.

For slowing weight loss in patients with cancer: 30 mL of a specific fish oil product (ACO Omega-3, Pharmacia, Stockholm, Sweden) providing 4.9 grams of EPA and 3.2 grams of DHA daily for 4 weeks has been used. 7.5 grams of fish oil daily providing EPA 4.7 grams and DHA 2.8 grams has been used for about 6 weeks. In addition, two cans of a fish oil nutritional supplement containing 1.09 grams of EPA and 0.96 grams of DHA per can have been used daily for up to 7 weeks.
It is well known that fish oil has the ability to improve vision. It also helps in avoiding age-related macular degeneration. The National Eye Institute at the National Institute of Health in the United States plans to conduct a nationwide study to evaluate the effect of fish oil in treating macular degeneration. This study will provide strong scientific evidence regarding the benefits of fish oil for eye care, thereby allowing government agencies and physicians to strongly recommend fish oil for macular degeneration.
4. Omega-3 has been found to save the lives of children going through short bowel syndrome (SBS), which is uncommon but impacts thousands of people in the United States. SBS can occur from birth (when a portion of the intestine fails to develop) or due to an infectious inflammatory disease striking premature newborns. In adults, it can be caused by surgery for Crohn's disease or injury.
Several small studies have shown that combination therapy with fish oil and HMG CoA reductase inhibitors is safe.56–61 The largest trial to date, the JELIS trial,32 was an open label trial of 18,645 Japanese adults with hypercholesterolemia who were randomized to a standard statin regimen or a fish oil formulation containing 1.8 g of EPA added to a statin medication. The cohort was made up mostly of postmenopausal, nonobese women with a 15% to 20% incidence of diabetes, tobacco use, or CAD. The primary outcome of any major cardiovascular event, at a mean of 4.6 years, was moderately reduced by a relative risk reduction of 26%. Both unstable angina and nonfatal MI were reduced, but no change was seen in sudden death. Overall, the findings were remarkable because at baseline approximately 90% of Japanese consumed at least 900 mg of EPA and DHA per day.62 The rates of cancer, joint pain, lumbar pain, or muscle pain were similar in the 2 groups. There was a similar rate of increase in measures of creatine phosphokinase, but more patients had an increase in aspartate aminotransferase levels (0.6% vs. 0.4%) in the fish oil group. The rate of bleeding was 1.1% in the fish oil combination group versus 0.6% in the HMG–CoA reductase inhibitor group.
36. Marchioli R, Barzi F, Bomba E, Chieffo C, Di Gregorio D, Di Mascio R, Franzosi MG, Geraci E, Levantesi G, Maggioni AP, et al. Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-Prevenzione. Circulation. 2002;105:1897–903. [PubMed]
42. Cawood AL, Ding R, Napper FL, Young RH, Williams JA, Ward MJ, Gudmundsen O, Vige R, Payne SP, Ye S, et al. Eicosapentaenoic acid (EPA) from highly concentrated n-3 fatty acid ethyl esters is incorporated into advanced atherosclerotic plaques and higher plaque EPA is associated with decreased plaque inflammation and increased stability. Atherosclerosis. 2010;212:252–9. [PubMed]
The absence of DHA in many pure EPA trials, and therefore lack of competition between EPA and DHA during digestion and consequently for uptake, is considered to be partly responsible for the positive outcomes. Simply put, pure EPA delivers more EPA into cells where it is needed than combined EPA & DHA blends. Consequently, oils containing DHA may not be suitable for a variety of conditions when treatment relies on increasing levels of EPA and its end products.
Cancer. Research on the effects of fish oil in preventing cancer has produced conflicting results. Some population research suggests that eating fish or having higher blood levels of omega-3 fatty acids from fish oil is linked to a lower risk of different cancers, including oral cancer, pharyngeal cancer, esophageal cancer, colon cancer, rectal cancer, breast cancer, ovarian cancer, and prostate cancer. But other research suggests that eating fish does not reduce the risk of cancer.