Studies have also shown that omega-3 fats are anti-arrhythmic (preventing or counteracting cardiac arrhythmia), anti-thrombotic (prevents thrombosis or a blood clot within a blood vessel), anti-atherosclerotic (preventing fatty deposits and fibrosis of the inner layer of your arteries), and anti-inflammatory (counteracting inflammation – the heat, pain, swelling, etc).
Dry eye disease occurs when tears don’t provide enough moisture, causing eye discomfort and vision problems. Some studies show that getting more omega-3s from foods or supplements—mainly EPA and DHA—helps relieve symptoms of dry eye disease. But a large, recent study found that the symptoms of people with dry eye disease who took fish oil supplements of 2,000 mg EPA plus 1,000 mg DHA daily for 1 year did not improve any more than those who took a placebo (a dummy pill). More research on the effects of omega-3s on dry eye disease is needed.
Omega AD study, Freund-Levi et al. (47) Double-blind, placebo-controlled, randomized 1741 DHA (1.7 g/d) and EPA (0.6 g/d) Decline in cognitive function did not differ between supplemented group and placebo group at 6 mo. However, patients with very mild cognitive dysfunction (n = 32, MMSE score >27) in the EPA+DHA-supplemented group had a significant reduction in MMSE score decline rate at 6 mo

If a chicken eats a diet heavy in omega-3s — such as flaxseed and other nutrient-dense grains — its eggs will be fortified with higher levels of those healthy fatty acids. If you can afford a little extra expense, look for omega-3-enriched eggs from humanely raised chickens that roam free and forage for insects and plants, which give the eggs even further nutrients and health benefits.
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)

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.
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.
A tremendous body of research has been conducted on these important nutrients since it was first discovered in the 1950s that fish oil offered many health benefits and that these benefits were attributable to a type of polyunsaturated fat called omega-3. Despite the volumes of research on omega-3s, it is only in recent years (within the last 15 years or so) that the actions of EPA and DHA have come to be understood individually. Researchers now often investigate the actions of EPA and DHA individually rather than together, no longer simply under the generic label omega-3 as they are widely referred to.
Fish oil supplements came under scrutiny in 2006, when the Food Standards Agency in the UK and the Food Safety Authority of Ireland reported PCB levels that exceeded the European maximum limits in several fish oil brands,[60][61] which required temporary withdrawal of these brands. To address the concern over contaminated fish oil supplements, the International Fish Oil Standards (IFOS) Program, a third-party testing and accreditation program for fish oil products, was created by Nutrasource Diagnostics Inc. in Guelph, Ontario, Canada.[62]
The differing actions of EPA and DHA, together with their competitive uptake, help to explain why studies that attempt to use standard fish oil therapeutically (where DHA and EPA are combined, in a natural ratio of approximately 1.5:1) are either less beneficial than expected, or even completely ineffective. Standard EPA/DHA fish oils are more suitable for everyday wellbeing, to compensate for a lack of fish in the diet and to meet a suggested intake.
One reason omega-3 fatty acids may be so beneficial to this many aspects of health could be that they help decrease system-wide inflammation. (49, 50, 51, 52, 53) Inflammation is at the root of most diseases and is related to the development of nearly every major illness, so by eating a nutrient-dense, anti-inflammatory diet, you give your body its best chance to fight disease like it was designed to do.
Omega 3 fatty acids are monounsaturated fats that come from food sources—primarily cold water fish (eg, salmon, trout, tuna, mackerel, and herring)—that contain EPA (eicosapentaenoic acid) and docosahexaenoic acid (DHA). Other fatty acids are derived from plant-derived sources of food—including nuts (especially walnuts) and seeds (eg, flax, chia, sunflower)—that have primarily ALA (alpha-linolenic acid).

Since EPA and DHA are both essential for health and appear together in nature, many studies have attempted to treat clinical conditions with combined EPA and DHA oils, but the outcomes have been varied, contradictory and disappointing. Consequently, researchers have started to investigate the individual actions of EPA and DHA in isolation, in numerous health conditions where an omega-3 deficiency is related to symptoms or known to play a causative role. The emerging evidence shows marked differences between how these two fatty acids affect us – not just at the cellular level but also the body as a whole.
If you find yourself in a position where you are just not eating any of these foods, and you want to get enough omega-3 fatty acids, then I think fish oil is okay, but I would limit not the amount of fish oil but the amount listed on the label of EPA and DHA combined. I would limit that amount to around 250 milligrams per day because I don’t think most people need more than that. Some signs that you might not be getting enough omega-3 fatty acids include chronic low-grade inflammation, poor visual acuity, slower mental processing, trouble learning, and possibly Alzheimer’s disease and psychiatric conditions, like depression, anxiety, and attention deficit and hyperactivity disorder, ADHD.
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.
ACS Breast Cancer Screening Guideline CDC Guideline for Prescribing Opioids CDC Guideline for Prevention of Surgical Site Infections Consensus Definitions for Sepsis and Septic Shock Global Burden of Cancer, 1990-2016 Global Burden of Disease in Children, 1990-2013 Global Burden of Hypertension, 1990-2015 Global Firearm Mortality, 1990-2016 Health Care Spending in the US and Other High-Income Countries Income and Life Expectancy in the US JNC 8 Guideline for Management of High Blood Pressure President Obama on US Health Care Reform Screening for Colorectal Cancer Screening for Depression in Adults Screening for Prostate Cancer Statins for Primary Prevention of Cardiovascular Disease The State of US Health, 1990-2016 US Burden of Cardiovascular Disease, 1990-2016 WMA Declaration of Helsinki, 7th Revision

There was a significantly greater association of treatment with reduced anxiety symptoms in participants receiving omega-3 PUFAs than in those not receiving omega-3 PUFAs in the subgroup with an EPA percentage less than 60% (k, 11; Hedges g, 0.485; 95% CI, 0.017-0.954; P = .04; Figure 4)35,49,52,54-61 but no significant difference in the association of treatment with reduced anxiety symptoms between participants receiving omega-3 PUFAs and those not receiving omega-3 PUFAs in the subgroup with an EPA percentage of at least 60% (k, 9; Hedges g, 0.092; 95% CI, –0.102 to 0.285; P = .35) (Figure 4).33,34,36,47,48,50,51,53,60 There were no significantly different estimated effect sizes between these 2 subgroups by the interaction test (P = .13).
Mozaffarian D, Marchioli R, Macchia A, Silletta MG, Ferrazzi P, Gardner TJ, Latini R, Libby P, Lombardi F, O'Gara PT, Page RL, Tavazzi L, Tognoni G; OPERA Investigators. Fish oil and postoperative atrial fibrillation: the Omega-3 Fatty Acids for Prevention of Post-operative Atrial Fibrillation (OPERA) randomized trial. JAMA 2012;308(19):2001-11. View abstract.

Three randomized trials assessing more than 600 patients with known malignant ventricular arrhythmia were carried out under the protection of implanted cardioverter defibrillator (ICD) therapy.41–43 In all 3 of the trials, 75% of the patients had ischemic heart disease, survived ventricular tachycardia or ventricular fibrillation and were randomized to 1 to 3 g/d of fish oil. In the first trial of its kind, 402 patients with ICDs were randomized to either a fish oil or an olive oil supplement.41 Although statistical significance was not reached, after approximately 1 year the primary end-point of time to first ICD cardioversion for ventricular tachycardia or fibrillation or death from any cause was longer in the fish oil group. This finding was not replicated in a trial of 200 patients who were randomized to either fish oil or a placebo and followed for a median of approximately 2 years.42 In fact, time to first ICD cardioversion was not changed and the incidence of recurrent ventricular tachycardia and fibrillation was more common in the group assigned to fish oil. In the largest trial, 546 patients were randomized to supplemental fish oil or a placebo and were followed for a mean period of 1 year.43 The primary outcome of the rate of ICD cardioversion or all-cause mortality was not reduced. It was concluded in a recent meta-analysis of these trials that fish oil did not have a protective effect.44
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
Bell, J. G., Miller, D., MacDonald, D. J., MacKinlay, E. E., Dick, J. R., Cheseldine, S., Boyle, R. M., Graham, C., and O'Hare, A. E. The fatty acid compositions of erythrocyte and plasma polar lipids in children with autism, developmental delay or typically developing controls and the effect of fish oil intake. Br J Nutr 2010;103(8):1160-1167. View abstract.
Eicosatetraenoic Acid (ETA): ETA is a lesser-known omega-3 fatty acid that also contains 20 carbons, like EPA, but only four bonds instead of five. It is found richly inroe oil and green-lipped mussel and is only recently being recognized for its potent health benefits. Not only is it anti-inflammatory, like the other omega-3s, but ETA can also limit your body’s production of the inflammatory omega-6 fatty acid arachidonic acid (ARA). In fact, ETA redirects the enzyme that normally creates ARA to convert it to EPA instead!
Findings  In this systematic review and meta-analysis of 19 clinical trials including 2240 participants from 11 countries, improvement in anxiety symptoms was associated with omega-3 polyunsaturated fatty acid treatment compared with controls in both placebo-controlled and non–placebo-controlled trials. The anxiolytic effects of omega-3 polyunsaturated fatty acids were also stronger in participants with clinical conditions than in subclinical populations.
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.
The biggest cause of omega-3 deficiency is the overconsumption of foods high in omega-6 fatty acids. Omega-6 comes from things like fried foods, fast foods and boxed foods that contain vegetables oils like soybean oil, canola oil, sunflower oil, cottonseed oil and corn oil. When you consume too much omega-6, it can decrease your body’s ability to metabolize healthy omega-3 fatty acids. (36)
Fish oil therapy is efficacious and safe for patients with severe to moderate hypertriglyceridemia. Combination therapy with HMG-CoA reductase inhibitors is also efficacious and has not been associated with any serious adverse reactions. Fish oil therapy added to fenofibrate in patients with severe hypertriglyceridemia is also effective and safe. Accordingly, it may be a safe and effective adjunct in the pharmacotherapy of the mixed lipid disorder that is frequently encountered in patients with the metabolic syndrome and/or type II diabetes mellitus.
Katzman  MA, Bleau  P, Blier  P,  et al; Canadian Anxiety Guidelines Initiative Group on behalf of the Anxiety Disorders Association of Canada/Association Canadienne des troubles anxieux and McGill University.  Canadian clinical practice guidelines for the management of anxiety, posttraumatic stress and obsessive-compulsive disorders.  BMC Psychiatry. 2014;14(suppl 1):S1. doi:10.1186/1471-244X-14-S1-S1PubMedGoogle ScholarCrossref
We included 79 RCTs (112,059 participants) in this review update and found that 25 were at low summary risk of bias. Trials were of 12 to 72 months’ duration and included adults at varying cardiovascular risk, mainly in high‐income countries. Most studies assessed LCn3 supplementation with capsules, but some used LCn3‐ or ALA‐rich or enriched foods or dietary advice compared to placebo or usual diet.
So why is an excess of DHA detrimental and an excess of EPA useful? DHA has a larger structure with two extra carbons and two extra double bonds, so it literally takes up more space in cell membranes than EPA. On the one hand, this is important because DHA plays a structural role in maintaining the fluidity of cell membranes ( essential for the normal function of proteins, channels and receptors that are also embedded in the membrane), but if a cell membrane becomes too saturated with DHA it can become too fluid, which can have a negative effect on cell function. EPA, on the other hand, is constantly utilised and always in demand.
Jump up ^ Heartney, Eleanor (2007). "Zhang Huan: Becoming the Body". Zhang Huan: Altered States. Charta and Asia Society. ISBN 978-8881586417. Retrieved 2014-10-23. This becomes abundantly clear in the work of Chinese body artist Zhang Huan. In the course of his career, Zhang Huan has subjected himself to painful trials: sitting motionless for hours in an outhouse covered in honey and fish oil while flies crawled over his body [...].
Anxiety, the most commonly experienced psychiatric symptom, is a psychological state derived from inappropriate or exaggerated fear leading to distress or impairment. The lifetime prevalence of any anxiety disorder is reported to be approximately 1 in 3.1 Anxiety is often comorbid with depressive disorders2 and is associated with lower health-related quality of life3 and increased risk of all-cause mortality.4 Treatment options include psychological treatments, such as cognitive-behavioral therapy and pharmacological treatments, mainly with selective serotonin reuptake inhibitors.5 Individuals with anxiety and related disorders tend to be more concerned about the potential adverse effects of pharmacological treatments (eg, sedation or drug dependence) and may be reluctant to engage in psychological treatments that can be time-consuming and costly, as well as sometimes limited in availability.6 Thus, evidence-based and safer treatments are required, especially for anxious patients with comorbid medical conditions.
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.
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]
Scaly, itchy skin (eczema). Research shows that fish oil does not improve eczema. Most research also shows that taking fish oil during pregnancy doesn't PREVENT eczema in the child. Giving fish oil to an infant also doesn't seem to prevent eczema in children. But children who eat fish at least once weekly from the age of 1-2 years seem to have a lower risk of developing eczema.
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