Fearon, K. C., Von Meyenfeldt, M. F., Moses, A. G., Van Geenen, R., Roy, A., Gouma, D. J., Giacosa, A., Van Gossum, A., Bauer, J., Barber, M. D., Aaronson, N. K., Voss, A. C., and Tisdale, M. J. Effect of a protein and energy dense n-3 fatty acid enriched oral supplement on loss of weight and lean tissue in cancer cachexia: a randomised double blind trial. Gut 2003;52(10):1479-1486. View abstract.
Under these conditions, it may make sense to try fish oil even at higher doses than what I recommended. There is some evidence that krill oil will get the omega-3 fatty acids better into the brain in the psychiatric conditions that I listed. And there is some evidence that EPA-rich fish oils are better than DHA-rich fish oils for some of those psychiatric conditions as well. So there’s room to play around with the different possibilities if those things apply to you. But for the average case, limit the fish oil to 250 milligrams of EPA and DHA combined when you take it, but in all cases, go for food first, and go for fish oil only after you have exhausted those possibilities.

1. Omega-3 benefits your heart health. An Italian study (GISSI)5 of 11,324 heart attack survivors found that patients supplementing with fish oils markedly reduced their risk of another heart attack, stroke, or death. In a separate study, 6 American medical researchers reported that men who consumed fish once or more every week had a 50 percent lower risk of dying from a sudden cardiac event than do men who eat fish less than once a month.
A scientific review published in 2013 looked at omega-3 polyunsaturated fatty acids and prostate cancer prevention. Researchers concluded that there’s a great deal of evidence suggesting that omega-3s have antiproliferative effects – which means they inhibit cancer cell growth – in cancer cell lines, animal models and humans. In addition, the “direct effects on cancer cells” and indirect anti-inflammatory effects on the immune system fighting the cancer likely contribute to the ability of omega-3 fatty acids to inhibit tumor growth. (14)
Abnormal rapid heart rhythms (ventricular arrhythmias). Population research suggests that eating a lot of fish has no effect on the risk for abnormal rapid heart rhythms. Clinical research is inconsistent. Some research shows that taking fish oil daily does not affect the risk for abnormal heart rhythms. But other research shows that taking fish oil for 11 months delays the development of the condition. However, overall, taking fish oil does not seem to reduce the risk of death in people with abnormal rapid heart rhythms.

6. Krauss-Etschmann S, Shadid R, Campoy C, Hoster E, Demmelmair H, Jimenez M, Gil A, Rivero M, Veszpremi B, Decsi T, et al. Effects of fish-oil and folate supplementation of pregnant women on maternal and fetal plasma concentrations of docosahexaenoic acid and eicosapentaenoic acid: a European randomized multicenter trial. Am J Clin Nutr. 2007;85:1392–400. [PubMed]
What makes omega-3 fats special? They are an integral part of cell membranes throughout the body and affect the function of the cell receptors in these membranes. They provide the starting point for making hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. They also bind to receptors in cells that regulate genetic function. Likely due to these effects, omega-3 fats have been shown to help prevent heart disease and stroke, may help control lupus, eczema, and rheumatoid arthritis, and may play protective roles in cancer and other conditions.
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.
Luo, J Rizkalla SW Vidal H Oppert JM Colas C Boussairi A Guerre-Millo M Chapuis AS Chevalier A Durand G Slama G. Moderate intake of n-3 fatty acids for 2 months has no detrimental effect on glucose metabolism and could ameliorate the lipid profile in type 2 diabetic men. Results of a controlled study. Diabetes Care. 1998;21(5):717-724. View abstract.
Full citation: Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, Deane KHO, AlAbdulghafoor FK, Summerbell CD, Worthington HV, Song F, Hooper L. Omega 3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2018, Issue 7. Art. No.: CD003177. DOI: 10.1002/14651858.CD003177.pub3.
Increased EPA levels in the blood and cell membranes effectively regulates inflammatory pathways and reduces total inflammatory ‘load’, so for any inflammatory conditions or concerns, we recommend a phase of pure EPA supplementation for at least 3-6 months. Pre-loading the body with pure EPA (without the opposing actions of DHA for uptake and utilisation) ensures constant replenishment of EPA ’supplies’ to support its high rate of turnover. Since DHA levels remain fairly stable and much lower daily amounts are required, DHA levels can be supported continually through dietary intake, or increased to 250 mg daily in later stages of treatment through supplementation.
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)

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.
The Department of Ecology of the State of Washington has ranked various seafood based on its EPA and DHA concentrations. The highest-ranking seafood is mackerel, excluding King mackerel, that has a concentration of 1,790 milligrams of combined EPA and DHA per 100 grams, followed by salmon at 1,590; bluefin tuna has between 1173 and 1504 milligrams; sardines contain 980 milligrams; albacore tuna has 862 milligrams; bass has 640 milligrams; tuna has 630 milligrams; trout and swordfish have 580 milligrams; and walleye has 530 milligrams. Other seafood, which includes sea bass, clams, lobster, scallops, catfish, cod, pollock, crayfish and scallops contains between 200 and 500 milligrams of EPA and DHA per 100 grams. Breaded fish products rank lowest on the list with only 0.26 milligram per 100 grams.
Thank you for your kind comment. As pointed out above, the main limitation of our meta-analysis is the heterogeneity, which we address several times in our main manuscript. We included studies with several different situations and participants with different underlying diseases, which would also result in wide heterogeneity in our meta-analysis. Based upon our post-hoc analysis, there was some common characteristics among the six trials with nominally significant results, including specific clinical diagnoses (5/6) and, placebo-control (4/6), which had also previously been addressed in our subgroup meta-analysis. Therefore, we suggested future placebo-controlled trials investigating the treatment effect of omega-3 in participants with specific clinical diagnoses should be warranted. In addition, improving underlying specific clinical diagnoses (5/6), good quality (placebo-control (4/6), low drop-out rate (zero in Exp/control groups: 4/6)), and long treatment duration (>= 12 weeks: 4/6) are all good indicators of high quality.
Oe, H., Hozumi, T., Murata, E., Matsuura, H., Negishi, K., Matsumura, Y., Iwata, S., Ogawa, K., Sugioka, K., Takemoto, Y., Shimada, K., Yoshiyama, M., Ishikura, Y., Kiso, Y., and Yoshikawa, J. Arachidonic acid and docosahexaenoic acid supplementation increases coronary flow velocity reserve in Japanese elderly individuals. Heart 2008;94(3):316-321. View abstract.
for canned sardines i noticed the omega 3 EPA/DHA levels (written on the can) varied between the different company brands (sometimes by a lot!) , and also, the EPA/DHA amounts varied depending on what was added in the can with the sardines (sunflower oil, olive oil, brine, spring water, etc --- little note: there's more fat in the oily fish, than found in the brine/spring water)
It helps maintain a good luster of the hair because omega-3 has growth stimulating properties since it provides nourishment to the follicles. It aids in the development of hair and in preventing hair loss. A good supply of protein is also necessary for hair growth, and since most fish varieties are rich in protein, eating fish helps to keep hair healthy.
Guallar, E., Aro, A., Jimenez, F. J., Martin-Moreno, J. M., Salminen, I., van't Veer, P., Kardinaal, A. F., Gomez-Aracena, J., Martin, B. C., Kohlmeier, L., Kark, J. D., Mazaev, V. P., Ringstad, J., Guillen, J., Riemersma, R. A., Huttunen, J. K., Thamm, M., and Kok, F. J. Omega-3 fatty acids in adipose tissue and risk of myocardial infarction: the EURAMIC study. Arterioscler.Thromb.Vasc.Biol 1999;19(4):1111-1118. View abstract.
Capanni, M., Calella, F., Biagini, M. R., Genise, S., Raimondi, L., Bedogni, G., Svegliati-Baroni, G., Sofi, F., Milani, S., Abbate, R., Surrenti, C., and Casini, A. Prolonged n-3 polyunsaturated fatty acid supplementation ameliorates hepatic steatosis in patients with non-alcoholic fatty liver disease: a pilot study. Aliment.Pharmacol.Ther. 4-15-2006;23(8):1143-1151. View abstract.
Fish oil has only a small benefit on the risk of premature birth.[43][44] A 2015 meta-analysis of the effect of omega−3 supplementation during pregnancy did not demonstrate a decrease in the rate of preterm birth or improve outcomes in women with singleton pregnancies with no prior preterm births.[45] A systematic review and meta-analysis published the same year reached the opposite conclusion, specifically, that omega−3 fatty acids were effective in "preventing early and any preterm delivery".[46]
In 1964 it was discovered that enzymes found in sheep tissues convert omega−6 arachidonic acid into the inflammatory agent called prostaglandin E2[71] which both causes the sensation of pain and expedites healing and immune response in traumatized and infected tissues.[72] By 1979 more of what are now known as eicosanoids were discovered: thromboxanes, prostacyclins, and the leukotrienes.[72] The eicosanoids, which have important biological functions, typically have a short active lifetime in the body, starting with synthesis from fatty acids and ending with metabolism by enzymes. If the rate of synthesis exceeds the rate of metabolism, the excess eicosanoids may, however, have deleterious effects.[72] Researchers found that certain omega−3 fatty acids are also converted into eicosanoids, but at a much slower rate. Eicosanoids made from omega−3 fatty acids are often referred to as anti-inflammatory, but in fact they are just less inflammatory than those made from omega−6 fats. If both omega−3 and omega−6 fatty acids are present, they will "compete" to be transformed,[72] so the ratio of long-chain omega−3:omega−6 fatty acids directly affects the type of eicosanoids that are produced.[72]
Currently, there isn’t a set standard recommendation for how many omega-3s we need each day, but suggestions range from a fish oil dosage of 500 to 1,000 milligrams daily depending on whom you ask. How easy is it to get these recommended amounts? To give you an idea, there are more than 500 milligrams of total omega-3s in one can of tuna fish and one small serving of wild-caught salmon.

Rogers, P. J., Appleton, K. M., Kessler, D., Peters, T. J., Gunnell, D., Hayward, R. C., Heatherley, S. V., Christian, L. M., McNaughton, S. A., and Ness, A. R. No effect of n-3 long-chain polyunsaturated fatty acid (EPA and DHA) supplementation on depressed mood and cognitive function: a randomised controlled trial. Br J Nutr 2008;99(2):421-431. View abstract.
The strongest evidence for a beneficial effect of omega-3 fats has to do with heart disease. These fats appear to help the heart beat at a steady clip and not veer into a dangerous or potentially fatal erratic rhythm. (1) Such arrhythmias cause most of the 500,000-plus cardiac deaths that occur each year in the United States. Omega-3 fats also lower blood pressure and heart rate, improve blood vessel function, and, at higher doses, lower triglycerides and may ease inflammation, which plays a role in the development of atherosclerosis. (1)
Sorgi, P. J., Hallowell, E. M., Hutchins, H. L. & Sears, B. (2007, January 17). Effects of an open-label pilot study with high-dose EPA/DHA concentrates on plasma phospholipids and behavior in children with attention deficit hyperactivity disorder. Nutrition Journal 6(16). Retrieved from http://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-6-16
Children: Fish oil is POSSIBLY SAFE when taken by mouth appropriately. Fish oil has been used safely through feeding tubes in infants for up to 9 months. But young children should not eat more than two ounces of fish per week. Fish oil is also POSSIBLY SAFE when given in the vein by a health care professional to infants who cannot take food by mouth. Fish oil is POSSIBLY UNSAFE when consumed from dietary sources in large amounts. Fatty fish contain toxins such as mercury. Eating contaminated fish frequently can cause brain damage, mental retardation, blindness and seizures in children.