A healthy balance of dietary omega 6 and omega 3 fatty acids is a prerequisite for normal immune function, cognitive health, and cardiovascular health. Among other factors, sufficient dietary levels of EPA, DHA or other omega 3 fatty acids are also important in the regulation of normal blood lipoprotein and healthy cholesterol metabolism. Fish oil supplements can also lower elevated triglyceride levels, improving cardiovascular health and reducing the risk of heart disease.†
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)
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).
McNamara, R. K., Able, J., Jandacek, R., Rider, T., Tso, P., Eliassen, J. C., Alfieri, D., Weber, W., Jarvis, K., DelBello, M. P., Strakowski, S. M., and Adler, C. M. Docosahexaenoic acid supplementation increases prefrontal cortex activation during sustained attention in healthy boys: a placebo-controlled, dose-ranging, functional magnetic resonance imaging study. Am J Clin Nutr 2010;91(4):1060-1067. View abstract.

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).


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.

Fatty predatory fish like sharks, swordfish, tilefish, and albacore tuna may be high in omega-3 fatty acids, but due to their position at the top of the food chain, these species may also accumulate toxic substances through biomagnification. For this reason, the United States Environmental Protection Agency recommends limiting consumption (especially for women of childbearing age) of certain (predatory) fish species (e.g. albacore tuna, shark, king mackerel, tilefish and swordfish) due to high levels of the toxic contaminant mercury. Dioxin, PCBs and chlordane are also present.[13] Fish oil is used as a component in aquaculture feed. More than 50 percent of the world's fish oil used in aquaculture feed is fed to farmed salmon.[14]
Other suspected health benefits of omega-3s and fish are less well established and need further study. They include suggestions of a reduced risk of breast cancer, colorectal cancer and possibly advanced prostate cancer, all related to eating fish rather than taking supplements. Some observational studies have associated omega-3s to a lower risk of cognitive decline, Alzheimer’s disease and dementia, as well as age-related macular degeneration.
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.
However, in both observational studies and controlled clinical trials, eating fish was shown to foster optimal development of a baby’s brain and nervous system, prompting advice that pregnant women and nursing mothers eat more fish rich in omega-3s while avoiding species that may contain mercury or other contaminants like PCBs sometimes found in freshwater fish.

We’ve written about the dose necessary to achieve measurable benefits before. However, a person’s actual omega-3 intake can be tricky to estimate. Even if you eat at least two servings of fatty fish per week, as the American Heart Association recommends (10), your fish might contain more or less omega-3s depending on the fish species, the time of year, and how you cook it. Even taking fish oil supplements isn’t always straightforward, as dose can be impacted by numerous bioavailability factors, as well as genetics, age, gender, medication-use and lifestyle.

Wright, S. A., O'Prey, F. M., McHenry, M. T., Leahey, W. J., Devine, A. B., Duffy, E. M., Johnston, D. G., Finch, M. B., Bell, A. L., and McVeigh, G. E. A randomised interventional trial of omega-3-polyunsaturated fatty acids on endothelial function and disease activity in systemic lupus erythematosus. Ann.Rheum.Dis. 2008;67(6):841-848. View abstract.
DHA is one of the most prevalent fatty acids in the brain. This could partly explain why our brains do better with a greater supply. A Rush Institute for Healthy Aging study analyzed fish-eating patterns of more than 800 men and women, ages 65 to 94. Those eating fish at least once a week were much less likely to develop Alzheimer's disease than those who turned up their nose at it.

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.

Second, quality matters. It is important to purchase fish oil from a reputable manufacturer that follows Good Manufacturing Practices (GMPs) and takes the necessary steps to purify the oil. In choosing a brand like Nature Made®, the #1 Pharmacist Recommended Omega-3/Fish Oil Brand*, you can rest assured knowing Nature Made has a strong commitment to making quality supplements so you can experience the benefits of fish oil.

The current American diet has changed over time to be high in SFA and low in omega-3 fatty acids (12). This change in eating habits is centered on fast food containing high amounts of saturated fat, which has small amounts of essential omega-3 PUFA compared with food prepared in the home (13). Seafood sources such as fish and fish-oil supplements are the primary contributors of the 2 biologically important dietary omega-3 fatty acids, EPA and DHA (14–16). This low intake of dietary EPA and DHA is thought to be associated with increased inflammatory processes as well as poor fetal development, general cardiovascular health, and risk of the development of Alzheimer's disease (AD).
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.

Fortier, M., Tremblay-Mercier, J., Plourde, M., Chouinard-Watkins, R., Vandal, M., Pifferi, F., Freemantle, E., and Cunnane, S. C. Higher plasma n-3 fatty acid status in the moderately healthy elderly in southern Quebec: higher fish intake or aging-related change in n-3 fatty acid metabolism? Prostaglandins Leukot.Essent.Fatty Acids 2010;82(4-6):277-280. View abstract.
According to independent laboratory[which?] tests, the concentrations of EPA and DHA in supplements can vary from between 8 and 80% fish oil content. The concentration depends on the source of the omega-3s, how the oil is processed, and the amounts of other ingredients included in the supplement.[52] A 2012 report claims 4 of 35 fish oil supplements it covered contained less[quantify] EPA or DHA than was claimed on the label, and 3 of 35 contained more[quantify][52] A ConsumerLab.com publication in 2010 claims 3 of 24 fish oil supplements it covered contained less[quantify] EPA and/or DHA than was claimed on the label.[48] However, the bioavailability of EPA and DHA from both capsular and emulsified fish oils has been shown to be high.[53]

So for those people who will not eat liver, cod liver oil on a daily basis can be a very good way of getting that. And you do benefit from the omega-3 fatty acids, and with the cod liver oil, it may even be unimportant to eat fish if you’re getting the cod liver oil, although it’s still better to focus on the fish, the egg yolks, and just add some of the cod liver oil.


Scaly, itchy skin (eczema). Fish oil might help PREVENT eczema, but research is not consistent. Some early research suggests that mothers who take fish oil supplements during pregnancy reduce the risk of severe eczema in their infants. Also, population research suggests that children who eat fish at least once weekly from 1 to 2 years of age have a lower risk of developing eczema. But other research, including recent studies, suggests that neither supplementation during pregnancy nor supplementation during infancy reduces the risk of eczema. Overall, research suggests that fish oil does not help TREAT eczema once it has developed.
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. 

The nutritional value of seafood is important during early development. The Dietary Guidelines for Americans 2015–2020 and guidance from the U.S. Food and Drug Administration and Environmental Protection Agency recommend that women who are pregnant or breastfeeding eat at least 8 ounces but no more than 12 ounces of a variety of seafood each week, from choices that are lower in methyl mercury. Methyl mercury can be harmful to the brain and nervous system if a person is exposed to too much of it. 
Makrides et al. (25) Double-blind, placebo-controlled, randomized 2399 (n = 1197 supplemented, n = 1202 placebo; 726 children were followed up with) DHA (fish-oil capsules providing 800 mg/d DHA) Supplementation did not result in lower levels of postpartum depression in mothers or improved cognitive and language development in offspring during early childhood
About the only exception are wild-caught Alaskan salmon and very small fish like sardines. The highest concentrations of mercury are found in large carnivorous fish like tuna, sea bass, and marlin. You may need to be especially cautious of canned tuna as well, as independent testing by the Mercury Policy Project found that the average mercury concentration in canned tuna is far over the "safe limits" of the Environmental Protection Agency (EPA).
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)
The studies examining the possible benefits of omega-3s continue. Researchers are looking at a range of health outcomes and the impact of a heart healthy diet rich in omega 3 fatty acids on a range of chronic disease. For instance, Dr. Hooper's team is beginning to evaluate the effects that omega-3 fats may have on diabetes, dementia, and some cancers.

A Pregnancy Prerequisite: Omega-3 fatty acids directly affect brain development, making it crucial for expectant mothers. Additionally, research indicates they decrease a mother's risk of depression. When the mother doesn't have enough of these essential fatty acids, the baby borrows from her. Some prenatal vitamins now include omega-3s, so be sure to check the label or grab a handful of walnuts each day.
Omega-3 fatty acids, which are found abundantly in fish oil, are increasingly being used in the management of cardiovascular disease. It is clear that fish oil, in clinically used doses (typically 4 g/d of eicosapentaenoic acid and docosahexaenoic acid) reduce high triglycerides. However, the role of omega-3 fatty acids in reducing mortality, sudden death, arrhythmias, myocardial infarction, and heart failure has not yet been established. This review will focus on the current clinical uses of fish oil and provide an update on their effects on triglycerides, coronary artery disease, heart failure, and arrhythmia. We will explore the dietary sources of fish oil as compared with drug therapy, and discuss the use of fish oil products in combination with other commonly used lipid-lowering agents. We will examine the underlying mechanism of fish oil’s action on triglyceride reduction, plaque stability, and effect in diabetes, and review the newly discovered anti-inflammatory effects of fish oil. Finally, we will examine the limitations of current data and suggest recommendations for fish oil use.
To date, no studies have assessed mortality or nonfatal MI in diabetic patients treated with fish oil.52–54 A recent comprehensive meta-analysis analyzed the effect of fish oil supplements on metabolic parameters when added to usual care in patients with type 2 diabetes mellitus or impaired glucose tolerance.54 The meta-analysis included a total of 23 small, randomized trials with over 1000 patients that were assessed for lipid and insulin resistance parameters. At a mean follow-up of approximately 9 weeks, triglyceride reduction was accomplished but no significant changes were seen in total cholesterol, high-density lipoprotein-cholesterol, HgA1c levels, fasting glucose levels, fasting insulin, or in body weight. The largest randomized trial to date assessed approximately 400 patients with impaired glucose tolerance or insulin-dependent diabetes mel-litus, and as reflected in the larger meta-analysis, found no effect of moderate to high doses of fish oil on diabetic parameters.55 There are insufficient randomized data to comment on the combination of fish oil and specific diabetes medications and related mortality and/or morbidity.

“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.”
Infant development. There is some evidence that mothers who eat fish or take fish oil supplements during pregnancy may improve some aspects of their baby's mental development. Taking fish oil during breast-feeding does not have this effect. However, feeding infants formula fortified with fish oil appears to improve some aspect of the baby's vision by the age of 2 months.
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