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)
Gajos G1, Rostoff P, Undas A, et al. Effects of polyunsaturated omega-3 fatty acids on responsiveness to dual antiplatelet therapy in patients undergoing percutaneous coronary intervention: the OMEGA-PCI (OMEGA-3 fatty acids after pci to modify responsiveness to dual antiplatelet therapy) study. J Am Coll Cardiol. 2010 Apr 20;55(16):1671-8. View abstract.
“The review provides good evidence that taking long-chain omega 3 (fish oil, EPA or DHA) supplements does not benefit heart health or reduce our risk of stroke or death from any cause.  The most trustworthy studies consistently showed little or no effect of long-chain omega 3 fats on cardiovascular health. On the other hand, while oily fish is a healthy food, it is unclear from the small number of trials whether eating more oily fish is protective of our hearts. 

Both omega−6 and omega−3 fatty acids are essential: humans must consume them in their diet. Omega−6 and omega−3 eighteen-carbon polyunsaturated fatty acids compete for the same metabolic enzymes, thus the omega−6:omega−3 ratio of ingested fatty acids has significant influence on the ratio and rate of production of eicosanoids, a group of hormones intimately involved in the body's inflammatory and homeostatic processes, which include the prostaglandins, leukotrienes, and thromboxanes, among others. Altering this ratio can change the body's metabolic and inflammatory state.[16] In general, grass-fed animals accumulate more omega−3 than do grain-fed animals, which accumulate relatively more omega−6.[86] Metabolites of omega−6 are more inflammatory (esp. arachidonic acid) than those of omega−3. This necessitates that omega−6 and omega−3 be consumed in a balanced proportion; healthy ratios of omega−6:omega−3, according to some authors, range from 1:1 to 1:4.[87] Other authors believe that a ratio of 4:1 (4 times as much omega−6 as omega−3) is already healthy.[88][89] Studies suggest the evolutionary human diet, rich in game animals, seafood, and other sources of omega−3, may have provided such a ratio.[90][91]
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.

Although there are no randomized data on fish oil consumption and protection from sudden death, observational studies have linked omega-3 FA with the prevention of sudden death. In a population-based, case-control study of sudden cardiac death victims, the mean red blood cell membrane omega-3 FA level of the lowest quartile, when compared with the mean level of the third quartile, was associated with a relative risk reduction of 70%.33 A similar finding was appreciated in a nested, prospective, case-control study of the Physician Health Study cohort of 22,000 healthy males. In the 119 patients that succumbed to sudden death, baseline omega-3 FA blood levels were significantly lower than in matched controls.34 Finally, in an analysis of data from the Nurses Health Study, a cohort study of 84,688 women, an inverse association was shown between fish consumption and CAD-related death. The investigators concluded that the reduction in CAD deaths was likely due to a reduction in sudden deaths, as there was no difference in the rate of MI when comparing high and low fish consumption.35


While fish for dinner is one way to get EPA and DHA, most people don’t eat the suggested two to three servings of oily fish per week to reap the benefits of omega-3s. What’s more, there are extremely few food sources, aside from fish, that naturally provide EPA and DHA. With all the benefits that can come from fish oil, it’s no surprise that these supplements are increasing in popularity.
A 2009 metastudy found that patients taking omega-3 supplements with a higher EPA:DHA ratio experienced fewer depressive symptoms. The studies provided evidence that EPA may be more efficacious than DHA in treating depression. However, this metastudy concluded that due to the identified limitations of the included studies, larger, randomized trials are needed to confirm these findings.[40]
Gajos, G., Zalewski, J., Rostoff, P., Nessler, J., Piwowarska, W., & Undas, A. (2011, May 26). Reduced thrombin formation and altered fibrin clot properties induced by polyunsaturated omega-3 fatty acids on top of dual antiplatelet therapy in patients undergoing percutaneous coronary intervention (OMEGA-PCI Clot). Arteriosclerosis, Thrombosis, and Vascular Biology 111.228593. Retrieved from http://atvb.ahajournals.org/content/early/2011/05/26/ATVBAHA.111.228593.abstract
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.

Sekikawa, A., Curb, D., Ueshima, H., El-Saed, A., Kadowaki, T., Abbott, R. D., ... Kuller, L. H. (2008 August 5). Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese Americans, and Whites: a cross-sectional study. Journal of the American College of Cardiology 52(6), 417–424. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2736602/
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 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.
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.
For those who do not eat seafood, another way exists for you to get a healthy dose of EPA and DHA each day. Fish oil supplements, which are rich in EPA and DHA, can be made from a variety of fish, with the most common ones being halibut, tuna, salmon, cod liver, mackerel and herring. On average, one 3.5 ounce serving of fatty fish contains about 1 gram of omega-3s, which can be obtained through fish oil supplements, according to MedlinePlus.
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.
Back in 2013, a study came out that made a lot of people concerned about fish oil supplements and cancer. The study, published in the Journal of the National Cancer Institute, showed that men who consume the largest amount of fish oil had a 71 percent higher risk of high-grade prostate cancer and a 43 percent increase in all types of prostate cancer. The study was conducted on 2,227 men, of which 38 percent of the men already had prostate cancer. (39)
Human diet has changed rapidly in recent centuries resulting in a reported increased diet of omega−6 in comparison to omega−3.[83] The rapid evolution of human diet away from a 1:1 omega−3 and omega−6 ratio, such as during the Neolithic Agricultural Revolution, has presumably been too fast for humans to have adapted to biological profiles adept at balancing omega−3 and omega−6 ratios of 1:1.[84] This is commonly believed to be the reason why modern diets are correlated with many inflammatory disorders.[83] While omega−3 polyunsaturated fatty acids may be beneficial in preventing heart disease in humans, the level of omega−6 polyunsaturated fatty acids (and, therefore, the ratio) does not matter.[78][85]
If you’ve been paying attention to health headlines over the last few decades, you’ve likely heard about essential fatty acids (EFAs) — specifically omega-3s and omega-6s. These nutrients play many vital roles in supporting our overall health, including increasing nutrient absorption, ensuring proper growth and development of the brain and nervous system, and reducing the risk of chronic illnesses, such as heart disease.  Click here for a guide to understanding omega-3 and omega-6 fatty acids and how they influence your health.
A certain kidney disease called IgA nephropathy. Some research shows that long-term but not short-term use of fish oil can slow the loss of kidney function in high-risk patients with IgA nephropathy. Fish oil might have greater effects when taken at higher doses. Also, it might be most effective in people with IgA nephropathy who have higher levels of protein in the urine.
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