In a U.K. study, children of mothers who ate more than 12 ounces a week actually scored better on tests of verbal I.Q., social behavior, and development and communication than children of mothers who ate none. In the Seychelles Islands, where people average 12 fish meals -- not ounces -- a week, there are no reports of links between mercury exposure and poor outcomes in children. These studies suggest that eating less than 12 ounces of fish each week could do more harm to a child's developing neurological system than mercury poisoning.
Sala-Vila A, Díaz-López A, Valls-Pedret C, et al.; Prevención con Dieta Mediterránea (PREDIMED) Investigators. Dietary marine ?-3 fatty acids and incident sight-threatening retinopathy in middle-aged and older individuals with type 2 diabetes: Prospective investigation from the PREDIMED trial. JAMA Ophthalmol. 2016;134(10):1142-1149. View abstract.
Weight loss. Some research shows that eating fish improves weight loss and decreases blood sugar in people who are overweight with high blood pressure. Early research also shows that taking a specific fish oil supplement (Hi-DHA, NuMega) lowers body fat when combined with exercise. But other evidence suggests that taking another specific fish oil supplement (Lovaza) does not lower body weight in overweight people.
Metagenics offers a wide range of educational opportunities including webinars, group meetings, and seminars as part of our commitment to continuing functional medicine education. Our goal is to give our practitioners further insight to help address their patients’ unique health needs for a higher level of personalized, lifetime wellness care. We have been sharing this ever-growing body of nutritional and lifestyle research for over 25 years.
Evidence in the population generally does not support a beneficial role for omega−3 fatty acid supplementation in preventing cardiovascular disease (including myocardial infarction and sudden cardiac death) or stroke.[4][19][20][21] A 2018 meta-analysis found no support that daily intake of one gram of omega-3 fatty acid in individuals with a history of coronary heart disease prevents fatal coronary heart disease, nonfatal myocardial infarction or any other vascular event.[6] However, omega−3 fatty acid supplementation greater than one gram daily for at least a year may be protective against cardiac death, sudden death, and myocardial infarction in people who have a history of cardiovascular disease.[22] No protective effect against the development of stroke or all-cause mortality was seen in this population.[22] Eating a diet high in fish that contain long chain omega−3 fatty acids does appear to decrease the risk of stroke.[23] Fish oil supplementation has not been shown to benefit revascularization or abnormal heart rhythms and has no effect on heart failure hospital admission rates.[24] Furthermore, fish oil supplement studies have failed to support claims of preventing heart attacks or strokes.[7]

This fact sheet by the Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.
Despite this one study, you should still consider eating fish and other seafood as a healthy strategy. If we could absolutely, positively say that the benefits of eating seafood comes entirely from omega-3 fats, then downing fish oil pills would be an alternative to eating fish. But it’s more than likely that you need the entire orchestra of fish fats, vitamins, minerals, and supporting molecules, rather than the lone notes of EPA and DHA.
Studies have also found that omega-3 fatty acids from fish oil are associated with improved survival rates for heart attack victims. A study published in the medical journal Circulation found that people who took a high dose of fish oil each for six months following the occurrence of a heart attack actually improved their hearts’ overall functioning and also reduced biomarkers of systemic inflammation. (20)
Krill oil is a source of omega−3 fatty acids.[116] The effect of krill oil, at a lower dose of EPA + DHA (62.8%), was demonstrated to be similar to that of fish oil on blood lipid levels and markers of inflammation in healthy humans.[117] While not an endangered species, krill are a mainstay of the diets of many ocean-based species including whales, causing environmental and scientific concerns about their sustainability.[118][119][120]
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.
Corresponding Author: Yutaka J. Matsuoka, MD, PhD, Division of Health Care Research, Center for Public Health Sciences, National Cancer Center Japan, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan (yumatsuo@ncc.go.jp); Kuan-Pin Su, MD, PhD, China Medical University Hospital, No. 2, Yude Road, North District, Taichung City, Taiwan 404 (cobolsu@gmail.com).
However, since the dosage of fish oil required for an ideal effect in the improvement of a patient is unknown, the Arthritis Center in the Department of Rheumatology at John Hopkins University considers including omega-3 fatty acids and fish oil in the treatment of arthritis as controversial. The University also cautions that arthritis patients must be wary of all the other side effects that can come from using fish oil. You can read more about arthritis on the web page of the Arthritis Foundation and the Arthritis Center.

In a 2009 joint study by the USDA and researchers at Clemson University in South Carolina, grass-fed beef was compared with grain-finished beef. The researchers found that grass-finished beef is higher in moisture content, 42.5% lower total lipid content, 54% lower in total fatty acids, 54% higher in beta-carotene, 288% higher in vitamin E (alpha-tocopherol), higher in the B-vitamins thiamin and riboflavin, higher in the minerals calcium, magnesium, and potassium, 193% higher in total omega−3s, 117% higher in CLA (cis-9, trans-11 octadecenoic acid, a cojugated linoleic acid, which is a potential cancer fighter), 90% higher in vaccenic acid (which can be transformed into CLA), lower in the saturated fats linked with heart disease, and has a healthier ratio of omega−6 to omega−3 fatty acids (1.65 vs 4.84). Protein and cholesterol content were equal.[86]
Jump up ^ Bloch MH, Qawasmi A (October 2011). "Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis". Journal of the American Academy of Child and Adolescent Psychiatry. 50 (10): 991–1000. doi:10.1016/j.jaac.2011.06.008. PMC 3625948. PMID 21961774.
Hooper, L., Thompson, R. L., Harrison, R. A., Summerbell, C. D., Ness, A. R., Moore, H. J., Worthington, H. V., Durrington, P. N., Higgins, J. P., Capps, N. E., Riemersma, R. A., Ebrahim, S. B., and Davey, Smith G. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ 4-1-2006;332(7544):752-760. View abstract.

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. 
Nine studies with 10 data sets used omega-3 PUFA dosages of less than 2000 mg/d.35,47,48,51,53,55,56,60,61 The main results revealed that there was no significant difference in the association of treatment with reduced anxiety symptoms between patients receiving omega-3 PUFA treatment and those not receiving it (k, 9; Hedges g, 0.457; 95% CI, –0.077 to 0.991; P = .09) (Figure 3B). Ten studies with 10 data sets used omega-3 PUFA dosages of at least 2000 mg/d.33,34,36,49,50,52,54,55,57-59 The main results revealed a significantly greater association of treatment with reduced anxiety symptoms in patients receiving omega-3 PUFA treatment than in those not receiving it (k, 11; Hedges g, 0.213; 95% CI, 0.031-0.395; P = .02) (Figure 3B). Furthermore, there was no significantly different estimated effect sizes between these 2 subgroups by the interaction test (P = .40).
One of the most well-known benefits of omega-3s are the way they positively affect risk factors associated with heart disease. That’s one reason the American Heart Association is very clear about encouraging people to get enough in their diets. (8) Heart disease and stroke are the leading causes of death worldwide, but communities who eat diets rich in fish have remarkably low instances of these diseases, which is at least partially due to their high omega-3 consumption. (9, 10)
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.
Several large trials have evaluated the effect of fish or fish oils on heart disease. In the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardio (known as the GISSI Prevention Trial), heart attack survivors who took a 1-gram capsule of omega-3 fats every day for three years were less likely to have a repeat heart attack, stroke, or die of sudden death than those who took a placebo. (2) Notably, the risk of sudden cardiac death was reduced by about 50 percent. In the more recent Japan EPA Lipid Intervention Study (JELIS), participants who took EPA plus a cholesterol-lowering statin were less likely to have a major coronary event (sudden cardiac death, fatal or nonfatal heart attack, unstable angina, or a procedure to open or bypass a narrowed or blocked coronary artery) than those who took a statin alone. (3)
ALA is an essential fatty acid, which means that you need it but you must get this fat from your diet because your body is unable to produce it. In general, omega 3 fats are a crucial component of all cell membranes, including the eye (retina) and brain as well as aiding in the process of energy production to support functions involving the heart, lungs, immune system, and hormones (endocrine system), work properly.1
My estimate is that close to 90 percent of fish oils on the market today may contain mercury and pesticide residues plus hydrogenated oils. Of course, this is my opinion based on my own research from visiting different manufacturing plants, interviewing companies, and studying the research and the listed ingredients of typical fish oils. I would stay away from ALL fish oils that do not have antioxidants like astaxanthin, which help stabilize the oil from going rancid. I always look for astaxanthin as part of any high-quality fish oil supplement.
If you have a bleeding disorder, bruise easily or take blood-thinning medications, you should use fish oil supplements with extra caution since large doses of omega-3 fatty acids can increase bleeding risk. This bleeding risk also applies to people with no history of bleeding disorders or current medication usage. If you have type 2 diabetes, you should only use fish oil supplements under your doctor’s supervision. Individuals with type 2 diabetes can experience increases in fasting blood sugar levels while taking fish oil supplements.

Some studies suggest that people who get higher amounts of omega-3s from foods and dietary supplements may have a lower risk of breast cancer and perhaps colorectal cancer. More research is needed to confirm this possible link. Whether omega-3s affect the risk of other cancers is not clear. Clinical trials to examine this possibility are in progress.


Additionally, total polychlorinated biphenyl (PCB) content was measured in every product. All product recorded PCB levels within the Food and Drug Administration’s (FDA) 2 PPM limit for the edible parts of fish/shellfish as well as the stricter standards enacted by California’s Proposition 65, which requires products containing greater than 0.09 PPM of PCB content to bear a cancer warning. The worst offender, Now Foods Ultra Omega-3 Fish Oil, recorded 0.04 PPM of PCB content.
Cast about for healthy canned tuna. Think all tuna is created equal? Think again. Choose canned light tuna instead of tuna steaks or albacore tuna. It tends to have less mercury. Albacore may contain three times the mercury of chunk light tuna. Check fish guides for the latest information about foods low in toxins but high in omega-3. Two good online sources are:

The chemical structure of eicosapentaenoic acid and docosahexaenoic acid. Eicosapentaenoic acid consists of 20 carbons (C20) with 5 double bonds, and the last unsaturated carbon is located third from the methyl end (n-3). Do-cosahexaenoic acid consists of 22 carbons (C22) with 6 double bonds, and also with the3 last unsaturated carbon located third from the methyl end (n-3). Adapted with permission from Frishman et al, eds. Cardiovascular Pharmacotherapeutics. New York, NY: McGraw Hill; 2003.3
During pregnancy and breastfeeding, eating 8 to 12 ounces per week of fish and other seafood may improve your baby’s health. However, it is important to choose fish that are higher in EPA and DHA and lower in mercury. Examples are salmon, herring, sardines, and trout. It is not clear whether taking dietary supplements containing EPA and DHA during pregnancy or breastfeeding affects a baby’s health or development. However, some studies show that taking these supplements may slightly increase a baby’s weight at birth and the length of time the baby is in the womb, both of which may be beneficial. Breast milk contains DHA. Most commercial infant formulas also contain DHA.
Jump up ^ Bloch MH, Qawasmi A (October 2011). "Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis". Journal of the American Academy of Child and Adolescent Psychiatry. 50 (10): 991–1000. doi:10.1016/j.jaac.2011.06.008. PMC 3625948. PMID 21961774.
The University of East Anglia (UEA) is a UK Top 15 university. Known for its world-leading research and outstanding student experience, it was awarded Gold in the Teaching Excellence Framework and  is a leading member of Norwich Research Park, one of Europe’s biggest concentrations of researchers in the fields of environment, health and plant science. www.uea.ac.uk.
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.

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ALA is an essential fatty acid, which means that you need it but you must get this fat from your diet because your body is unable to produce it. In general, omega 3 fats are a crucial component of all cell membranes, including the eye (retina) and brain as well as aiding in the process of energy production to support functions involving the heart, lungs, immune system, and hormones (endocrine system), work properly.1
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.
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