The human body can make most of the types of fats it needs from other fats or raw materials. That isn’t the case for omega-3 fatty acids (also called omega-3 fats and n-3 fats). These are essential fats—the body can’t make them from scratch but must get them from food. Foods high in Omega-3 include fish, vegetable oils, nuts (especially walnuts), flax seeds, flaxseed oil, and leafy vegetables.

Omega-3s have been studied in various mood disorders, such as postpartum depression, with some promising results. In bipolar disorder (manic depression), the omega-3s may be most effective for the depressed phase rather than the manic phase of the illness. The omega-3s have also been proposed to alleviate or prevent other psychiatric conditions including schizophrenia, borderline personality disorder, obsessive compulsive disorder, and attention deficit disorder. However, there is still not enough evidence to recommend the omega-3s in these conditions.
I now suspect that those thousands of gel-covered capsules I’ve swallowed over the years may have done little more than enrich the pockets of supplement producers and sellers. A number of extensive analyses have been conducted, some supporting and others refuting the value of fish oils to the cardiovascular system, along with studies of other purported health benefits that also have had mixed results.

Fish Oil capsules contain omega-3 polyunsaturated fatty acids. Omega-3 polyunsaturated fatty acids are found in oils from certain types of fish, vegetables, and other plant sources. These fatty acids are not made by the body and must be consumed in the diet. Omega-3 polyunsaturated fatty acids work by lowering the body's production of triglycerides. High levels of triglycerides can lead to coronary artery disease, heart disease, and stroke.
The GISSI-Prevenzione trial40 showed similar findings. In this open-label trial, 11,324 post-MI patients were followed for 3.5 years after randomization to either 1 g/d of omega-3 FA, vitamin E, both, or none. In the 2836 patients assigned to only omega-3 FA, the primary end point of death, nonfatal MI or stroke, was reduced by 10%. This decreased risk occurred despite a minimal triglyceride-lowering effect because of the relatively low dose of omega-3 FA. Of note, the GISSI-Prevenzione trial was done prior to the pervasive use of lipid-lowering agents. Only about 40% of patients were on any form of lipid-lowering therapy.
Your concerns are very valid. The quality of commercially available omega-3 preparations can vary greatly. In our clinical trials we use preparations made by reputable manufacturers with high standards. We also have the preparations analyzed by 2 independent labs to confirm omega-3 content, impurities, and degree of oxidation, prior to initiating the study. While omega-3 fatty acids–like most nutrients–are ideally obtained through dietary practice, because many people may not enjoy omega-3 containing foods, supplements may be a good option for these individuals. Anyone who is interested in using an omega-3 preparation for treating a psychiatric condition should do so preferably under the supervision of a psychiatrist.
Omega-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential nutrients that have potential preventive and therapeutic effects on psychiatric disorders, such as anxiety and depression,7-15 as well as comorbid depression and anxiety in physically ill patients,16-19 patients with coronary heart disease,20,21 and pregnant women.22,23 Preclinical data support the effectiveness of omega-3 PUFAs as treatment for anxiety disorders. Song et al24,25 found that an EPA-rich diet could reduce the development of anxiety-like behaviors in rats as well as normalize dopamine levels in the ventral striatum. In addition, Yamada et al26 showed that a high dietary omega-3 to omega-6 PUFA ratio reduced contextual fear behaviors in mice and that these effects were abolished by a cannabinoid CB1 receptor antagonist.
Omega 3 fatty acids—found in supplements and naturally in some foods like certain fish, and nuts and seeds—have long been touted for their health benefits, especially heart health. Yet, a lot is still unknown, including whether it's better to get your omega 3 fats from pills or in food—and the debate continues regarding how much they may actually help you avoid heart disease.
Human studies also confirm cognition and memory improvement with omega-3 supplementation. For example, a study showed that both fish oil and krill oil enhanced cognitive function in a group of older men by increasing oxygen delivery to their brains. Interestingly, for those taking krill oil this effect was more prominent than those taking fish oil, though both groups were significantly better than placebo.30 As we pointed out earlier, because the omega-3 DHA is bound to phospholipids in krill it may be more effectively incorporated into the critical cell membrane in brain cells.
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Scientific studies have found that fish oil can help to prevent and kill various cancers, including colon, prostate and breast. (13a) Not only has research proven that it makes conventional cancer drugs more effective, but it’s also an effective stand-alone therapy in natural cancer treatment. Intravenous fish oil lipid emulsions, in particular, are rich in omega-3 polyunsaturated fatty acids, which exhibit anti-inflammatory and immunomodulatory effects. (13b)
All people need to consume omega-3 fats regularly. The recommended daily intake for adults is 1.6 grams for males  and 1.1 grams for females, according to the National Institutes of Health. The omega-3 family encompasses numerous fatty acids, but three primary forms are eicosapentaenoic acid, docosahexaenoic acid, and alpha-linolenic acid. The first two forms primarily occur in fish, such as salmon, mackerel, and tuna. The third can be found in plant oils, including flaxseed, soybean, walnut, and canola oils.
Omega-3s have been studied for other conditions, with either inconclusive or negative results. These conditions include allergies, atopic eczema (an allergic skin condition), cystic fibrosis, diabetes, inflammatory bowel diseases (Crohn’s disease or ulcerative colitis), intermittent claudication (a circulatory problem), nonalcoholic fatty liver disease, and osteoporosis. 
There’s evidence that points to the mechanism behind the effects of fish oil on body composition, showing that fat burning at rest is increased with 6 grams/day of fish oil supplementation, and additional research suggests that higher omega-3 levels may be helpful for enhancing satiety during weight loss efforts. Other evidence suggests that fat loss may be a side-effect of the reduction in inflammation that fish oil can help with. Any way you look at it, supporting your dietary habits with 4 or more grams of fish oil per day is probably a good idea!
The US National Institutes of Health lists three conditions for which fish oil and other omega-3 sources are most highly recommended: hypertriglyceridemia (high triglyceride level), preventing secondary cardiovascular disease, and hypertension (high blood pressure). It then lists 27 other conditions for which there is less evidence. It also lists possible safety concerns: "Intake of 3 grams per day or greater of omega-3 fatty acids may increase the risk of bleeding, although there is little evidence of significant bleeding risk at lower doses. Very large intakes of fish oil/omega-3 fatty acids may increase the risk of hemorrhagic (bleeding) stroke."[12]
Another small study had all volunteers consume the same exact control diet and substituted fish oil for visible fats (things like butter and cream). The volunteers consumed six grams of fish oil each day for three weeks. They found that body fat mass decreased with the intake of fish oil. The researchers conclude that dietary fish oil reduces body fat and stimulates the use of fatty acids for the production of energy in healthy adults. (33a)

Mercury and polychlorinated biphenyls (PCBs) are common toxins in seafood. Although the U.S. banned the use of PCBs and DDT in 1976, these and other chemicals are still used in half the world's commercial chemical processes. Substances like these can hang around in the air, soil, and water for many years. They end up in the bodies of fish and animals.

The health benefits of fish oil can be incredible for the body’s largest organ, the skin. This source of essential fats improves the health and beauty of human skin in several ways. Fish oil benefits and nourishes the skin with fats and contributes fat-soluble vitamins that help skin maintain a smooth, elastic texture. There is also evidence that fish oil prevents wrinkles and works against the aging process.
Lok CE, Moist L, Hemmelgarn BR, Tonelli M, Vazquez MA, Dorval M, Oliver M, Donnelly S, Allon M, Stanley K; Fish Oil Inhibition of Stenosis in Hemodialysis Grafts (FISH) Study Group. Effect of fish oil supplementation on graft patency and cardiovascular events among patients with new synthetic arteriovenous hemodialysis grafts: a randomized controlled trial. JAMA 2012;307(17):1809-16. View abstract.

There is also evidence that mothers who use EPA and DHA supplementation during pregnancy and breastfeeding may protect their children against allergies. This may be due to the fact that fish-oil supplementation has been associated with decreased levels of body cells associated with inflammation and immune response (26). In a study about food allergy and IgE-associated eczema, the period prevalence of food allergy was lower in the maternal EPA+DHA supplementation group compared to placebo (P < 0.05), and the incidence of IgE-associated eczema was also lower in the maternal EPA+DHA supplementation group compared to placebo (P < 0.05) (27).
Humans can convert short-chain omega−3 fatty acids to long-chain forms (EPA, DHA) with an efficiency below 5%.[73][74] The omega−3 conversion efficiency is greater in women than in men, but less studied.[75] Higher ALA and DHA values found in plasma phospholipids of women may be due to the higher activity of desaturases, especially that of delta-6-desaturase.[76]
A six week, double-blind study on fish oil supplementation for body composition showed that the group taking 4 grams/day of fish oil (contained 1600mg if EPA & 800mg of DHA) experienced a significant increase in lean body mass and significant decrease in fat mass compared to a group that took safflower oil (an omega-6 oil). The fish oil group also saw a tendency for decreases in cortisol, a hormone associated with belly fat gain when elevated.
Bo and I worked with Dr. Harris many years ago to measure the impact of eating one Omega Cookie® daily on the study participants’ omega-3 index levels, and we recently ran into him at ISFFAL. At the conference, we remeasured our omega-3 index and omega-6/omega-3 ratios, and a few weeks later, we got our results in the mail. For the two of us, it was exciting to get another concrete measure of how our daily omega-3 consumption impacted our scores. For the record, we take one vial of Omega Restore™ per night and frequently sneak an Omega Heaven® or Omega Cookie during the day.

Even healthy oils form trans fats when heated. Each oil has a different temperature at which it forms its own trans fats. Generally, when the oil begins to smoke is when trans fats are formed. Did this study consider how and at what temperatures the fish were cooked? Are some of the suppliments heated before being made into capsules? Did it also consider that many types of fish have dangerous levels of mercury?
Omega-3s are important components of the membranes that surround each cell in your body. DHA levels are especially high in retina (eye), brain, and sperm cells. Omega-3s also provide calories to give your body energy and have many functions in your heart, blood vessels, lungs, immune system, and endocrine system (the network of hormone-producing glands).
First difference is in the area of omega-6 fatty acid metabolism. Whereas EPA is the inhibitor of the enzyme (D5D) that directly produces AA, DHA is an inhibitor of another key enzyme delta-6-desaturase (D6D) that produces the first metabolite from linoleic acid known as gamma linolenic acid or GLA (6). However, this is not exactly an advantage. Even though reduction of GLA will eventually decrease AA production, it also has the more immediate effect of reducing the production of the next metabolite known as dihomo gamma linolenic acid or DGLA. This can be a disaster as a great number of powerful anti-inflammatory eicosanoids are derived from DGLA. This is why if you use high-dose DHA it is essential to add back trace amounts of GLA to maintain sufficient levels of DGLA to continue to produce anti-inflammatory eicosanoids.
We hypothesized that omega-3 PUFAs might have anxiolytic effects in patients with significant anxiety- and fear-related symptoms. However, there have been no systematic reviews of this topic to date. Thus, we examined the anxiolytic effects of omega-3 PUFAs in participants with elevated anxiety symptoms in the results of clinical trials to determine the overall efficacy of omega-3 PUFAs for anxiety symptoms irrespective of diagnosis.
If you want to take higher doses of omega-3 fish oil supplements, talk to your doctor first. Your doctor can guide you in supplementing your diet with omega-3 fish oil. Also, your doctor can monitor all aspects of your health if you take higher doses of fish oil.For people with very high triglyceride levels, prescription omega-3 preparations are also available.
Fish oils seem to help reduce some fat levels in the blood. These fats are called triglycerides. Birth control pills might decrease the effectiveness of fish oils by reducing these fat levels in the blood.Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.