Fish oil seems to be a subject of controversy. Some people swear by it, and there are thousands of clinical trials out now trying to study what the latest and greatest thing about the supplement is. The Natural Standard does a really good job collecting and gathering data for those who are interested in delving through what fish oil may or may not be doing to us. Definitive answers, however, may take a little while to get.
Most brands of fish oil have been proven safe, free of detectable traces of mercury, and do not contain unsafe levels of PCBs (polychlorinated biphenyls), a toxin and pollutant believed to pose various health threats. To avoid contaminants in an unrefined supplement, it's best to choose a fish-oil supplement made from small, oily fish like anchovy, sardines or menhaden.
The American Heart Association (AHA) recommends that everyone eats fish (particularly fatty, coldwater fish) at least twice a week. Salmon, mackerel, herring, sardines, lake trout, and tuna are especially high in omega-3 fatty acids. While foods are your best bet for getting omega-3s in your diet, fish oil supplements are also available for those who do not like fish. The heart-healthy benefits of regular doses of fish oil supplements are unclear, so talk to your doctor to see if they're right for you. If you have heart disease or high triglyceride levels, you may need even more omega-3 fatty acids. Ask your doctor if you should take higher doses of fish oil supplements to get the omega-3s you need.
“This idea has since been pretty discredited; we really don’t know if the Eskimos got heart disease or not,” said Malden C. Nesheim, emeritus professor of nutrition at Cornell University, who chaired an Institute of Medicine committee assessing the risks and benefits of seafood in the early 2000s. “I’ve been an omega-3 skeptic since doing this study.”
Fish oils might slow blood clotting. Taking fish oils along with medications that also slow clotting might increase the chances of bruising and bleeding.Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.

Some studies reported better psychomotor development at 30 months of age in infants whose mothers received fish oil supplements for the first four months of lactation.[45] In addition, five-year-old children whose mothers received modest algae based docosahexaenoic acid supplementation for the first 4 months of breastfeeding performed better on a test of sustained attention. This suggests that docosahexaenoic acid intake during early infancy confers long-term benefits on specific aspects of neurodevelopment.[45]

Muñoz MA, Liu W, Delaney JA, Brown E, Mugavero MJ, Mathews WC, Napravnik S, Willig JH, Eron JJ, Hunt PW, Kahn JO, Saag MS, Kitahata MM, Crane HM. Comparative effectiveness of fish oil versus fenofibrate, gemfibrozil, and atorvastatin on lowering triglyceride levels among HIV-infected patients in routine clinical care. J Acquir Immune Defic Syndr 2013;64(3):254-60. View abstract.


Haberka, M., Mizia-Stec, K., Mizia, M., Janowska, J., Gieszczyk, K., Chmiel, A., Zahorska-Markiewicz, B., and Gasior, Z. N-3 polyunsaturated fatty acids early supplementation improves ultrasound indices of endothelial function, but not through NO inhibitors in patients with acute myocardial infarction: N-3 PUFA supplementation in acute myocardial infarction. Clin.Nutr. 2011;30(1):79-85. View abstract.
If, however, we want to target the actions and benefits of either fat for more intensive support or clinical use, we need to alter the natural 1.5:1 EPA:DHA ratio found in most omega-3 sources such as fish oil – which is when concentrated supplements are especially useful. Certain forms of omega-3 called ethyl-ester and re-esterified triglyceride give nature a helping hand – allowing us to achieve targeted ratios of specific fatty acids at high concentration and physiologically active doses.
For rheumatoid arthritis, one systematic review found consistent, but modest, evidence for the effect of marine n−3 PUFAs on symptoms such as "joint swelling and pain, duration of morning stiffness, global assessments of pain and disease activity" as well as the use of non-steroidal anti-inflammatory drugs.[35] The American College of Rheumatology has stated that there may be modest benefit from the use of fish oils, but that it may take months for effects to be seen, and cautions for possible gastrointestinal side effects and the possibility of the supplements containing mercury or vitamin A at toxic levels. The National Center for Complementary and Integrative Health has concluded that "[n]o dietary supplement has shown clear benefits for rheumatoid arthritis", but that there is preliminary evidence that fish oil may be beneficial, but needs further study.[36]
DHA is especially vital for infant and child brain and nervous system development, as well as visual function. In older children, high DHA levels have been shown to improve learning ability, while deficiencies have been linked to learning problems and ADHD. And in adults, some studies have shown that DHA helps protect against cognitive decline and Alzheimer’s disease.
The health benefits of fish oil include its ability to aid in weight loss and healthy pregnancy. It also promotes fertility and skin care (particularly for psoriasis and acne). It is beneficial in the treatment of various heart diseases, high cholesterol, depression, anxiety, ADHD, weak immune system, cancer, diabetes, inflammation, arthritis, IBD, AIDS, Alzheimer’s disease, eye disorders, macular degeneration, and ulcers.

People should get most of their nutrients from food, advises the federal government's Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber, and other substances that benefit health. In some cases, fortified foods and dietary supplements may provide nutrients that otherwise may be consumed in less-than-recommended amounts. For more information about building your own healthy eating pattern, visit ChooseMyPlate.gov. MyPlate offers messages, resources, and tools to help you make the choices that are right for you, based on the Dietary Guidelines for Americans.


Some people who are hypersensitive to fish or have a known allergy to fish products may have a negative reaction to fatty acids which were derived from fish. Some fish oil tablets are also produced with alpha-linolenic acids which come from nuts, which may aggravate those which have an allergy to these products. In many cases these allergies will manifest themselves as a skin rash, but the symptoms could be more severe depending on the severity of your allergies. People with this concern will need to avoid using these products.
Thanks for the informative article. You mentioned that those taking high doses of DHA should supplement it with trace amounts of GLA. What GLA source would you recommend, and how much per day? I will be taking around 3400 mg of epa and 2200 mg DHA per day. I've heard that Borage Oil is more potent in GLA than evening primrose, but that it can lead to increased clotting and increased risk of heart attack, stroke, etc due to increased thromboxane B2. The main reason I want to stay away from the primrose is because it is extremely rich in linoleic acid. Thanks.
A new Cochrane systematic review, published today in the Cochrane Library, combines the results of seventy-nine randomised trials involving 112,059 people. These studies assessed effects of consuming additional omega 3 fat, compared to usual or lower omega 3, on diseases of the heart and circulation. Twenty-five studies were assessed as highly trustworthy because they were well designed and conducted.
Nonetheless, large population studies with solid data both on the participants’ diets and causes of disease and death bolstered the beliefs that eating fish often was a heart-healthy practice linked to reduced rates of cardiovascular disease. For example, a comprehensive analysis conducted by Dr. Dariush Mozaffarian and Eric Rimm of the Harvard T.H. Chan School of Public Health found that eating two servings of fatty fish a week — equal to about two grams of omega-3 fatty acids — lowered the risk of death from heart disease by more than a third and total deaths by 17 percent.

The GISSI-Heart Failure trial was the first blinded, randomized trial to assess the efficacy of fish oil supplements in patients with heart failure.51 The trial enrolled 7046 subjects with heart failure; 60% with New York Heart Association class II symptoms and 40% with a history of MI. The majority of patients were on a standard heart failure regimen, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, beta-blockers, and spironolactone, but only 22% were on a statin. At an average of 3.9 years, the coprimary end points of death and death or hospital admission for cardiovascular reasons were reduced by approximately 9% with fish oil supplementation. Sudden cardiac death, a secondary end-point, showed a statistically nonsignificant relative risk reduction of 7% with fish oil. There was also a reduction in 2 other arrhythmia-related secondary end-points: first hospitalization for ventricular arrhythmia and presumed arrhythmic death.
Human growth and intellectual development – DHA plays a very important role during fetal development, early infancy and old age. High concentrations of DHA are found in the brain and increase 300 to 500 percent in an infant’s brain during the last trimester of pregnancy. Adding DHA to a pregnant mother’s diet may be beneficial for the fetus’s brain development. Elderly people should also take EPA DHA, because as we get older, our bodies form less EPA and DHA, which may cause less mental focus and cognitive function. Taking EPA DHA also may help with mental abnormalities, such as Alzheimer’s disease and dementia.
After a large number of lab studies found that omega-3 fatty acids may be effective in slowing or reversing the growth of hormonal cancers, namely prostate and breast cancer cells, animal and human epidemiological studies have been conducted to see whether this effect occurred in real-life scenarios. The evidence is somewhat conflicting in some reports, but there is some evidence to suggest breast and prostate cancers may be potentially slowed (or the risk reduced) in people who eat a lot of oily fish and possibly those who supplement with omega-3. (66, 67, 68)
People with metabolic syndrome (the combination of central obesity, high blood pressure, disturbed lipid profile, and impaired glucose tolerance) are at increased risk of death from cardiovascular disease, diabetes, cancer, and other apparently “age-related” disorders. Because metabolic syndrome is closely associated with chronic low-grade inflammation, the powerful anti-inflammatory effects of omega-3 fats are especially important as a means of slowing or stopping the progression of this deadly disorder.

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.
Higdon JV, Liu J, Du S, et al. Supplementation of postmenopausal women with fish oil rich in eicosapentaenoic acid and docosahexaenoic acid is not associated with greater in vivo lipid peroxidation compared with oils rich in oleate and linoleate as assessed by plasma malondialdehyde and F(2)- isoprostanes. Am J Clin Nutr 2000;72:714-22. View abstract.
Jump up ^ Talakoub, Lily; Neuhaus, Isaac M.; Yu, Siegrid S. (2008). "Chapter 2: Cosmoceuticals". In Alam, Murad; Gladstone, Hayes B.; Tung, Rebecca. Cosmetic Dermatology. Requisites in dermatology. Elsevier Health Sciences. p. 9. ISBN 9780702031434. Retrieved 2014-10-23. Other oils used as emollients include fish oil, petrolatum, shea butter, and sunflower seed oil.

There are three types of omega-3 fatty acids, which include EPA, DHA and ALA, which is alpha-linoleic acid. Although EPA and DHA are found to have high amounts from animal sources, ALA is found in rich concentrations in plant sources, including certain vegetable oils and flaxseeds, although fatty fish and shellfish are the best sources of EPA and DHA, according to the National Center for Complementary and Alternative Medicine. Examples of these fatty fish and shellfish include salmon, tuna, trout, crab, oysters and mussels.

Children require DHA for growth and development, and the brain, CNS and retina rely heavily on the adequate supply of DHA during growth in the womb. Thus women should emphasise DHA in their diets when they become pregnant and continue to take this until they cease breastfeeding. Children continue to need DHA up until the age they start school, so if children under the age of five are taking an omega-3 supplement, it should contain DHA. The exception is for children with developmental problems – where pure EPA or high EPA omega-3 has been shown to be most effective for supporting cognitive function. We would still recommend, where possible, naturally derived sources of omega-3 such as oily fish to support a balanced EPA and DHA intake.

Participants treated with a daily dose of 2000 mg or more of omega-3 PUFAs showed a significantly greater association of treatment with reduced anxiety symptoms. In addition, participants receiving supplements containing less than 60% EPA showed a significant association, but not those receiving supplements containing 60% or more EPA. The depression literature supports the clinical benefits of EPA-enriched formulations (≥60% or ≥50%) compared with placebo for the treatment of clinical depression.9,13,73-75 This opposite effect of EPA-enriched formations on anxiety and depression is intriguing and possibly linked to a distinct underlying mechanism of omega-3 PUFAs. Exploration of the effects of omega-3 PUFAs on anxiety symptoms is just beginning and studies assessing the dose response anxiolytic effects of omega-3 PUFAs have not yet been performed. Further phase 2 trials of anxiety symptoms among participants with neuropsychiatric illness or physical illness should aim to determine the optimal dose.
Given the wide-ranging importance and benefits of marine omega-3 fatty acids, it is important to eat fish or other seafood one to two times per week, particularly fatty (dark meat) fish that are richer in EPA and DHA. This is especially important for women who are pregnant or hoping to become pregnant and nursing mothers. From the third trimester until the second year of life, a developing child needs a steady supply of DHA to form the brain and other parts of the nervous system. Many women shy away from eating fish because of concerns that mercury and other possible contaminants might harm their babies, (9) yet the evidence for harm from lack of omega-3 fats is far more consistent, and a balance of benefit vs. risk is easily obtained. (To learn more about the controversy over contaminants in fatty fish, read Fish: Friend or Foe.)

The evidence that fish oil consumption should be used for primary prevention of CAD is based on observational studies. The only randomized trial for primary prevention, the JELIS trial, showed a moderate relative risk reduction and was conducted in a very specific group. Nevertheless, to date, there has been no strong signal suggesting any serious adverse effects of having high DHA and EPA oils in the diet. We agree with the national guidelines that one should consume moderate amounts of fish oil— either in supplement or through the dietary intake of fatty fish with low mercury levels.


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).
Chemical structure of alpha-linolenic acid (ALA), an essential omega−3 fatty acid, (18:3Δ9c,12c,15c, which means a chain of 18 carbons with 3 double bonds on carbons numbered 9, 12, and 15). Although chemists count from the carbonyl carbon (blue numbering), biologists count from the n (ω) carbon (red numbering). Note that, from the n end (diagram right), the first double bond appears as the third carbon-carbon bond (line segment), hence the name "n-3". This is explained by the fact that the n end is almost never changed during physiological transformations in the human body, as it is more energy-stable, and other compounds can be synthesized from the other carbonyl end, for example in glycerides, or from double bonds in the middle of the chain.
Preventing re-blockage of blood vessels after angioplasty, a procedure to open a closed blood vessel. Research suggests that fish oil decreases the rate of blood vessel re-blockage by up to 45% when given for at least 3 weeks before an angioplasty and continued for one month thereafter. But, when given for 2 weeks or less before angioplasty, it doesn't seem to have any effect.
×