What Is Fish Oil and Is It Really That Good For You?

Earlier trials of fish and omega-3 supplements showed improved cardiovascular disease outcomes, such as decreased all-cause mortality and sudden cardiac death. These trials provided basis for recommendations of supplementation with fish oil. (1) However, since about 2010, results from primary and secondary prevention trials tend to show no benefit, and many studies have shown that fish oil supplements are both highly oxidized and lower in omega-3s than what’s stated on the label. (2)

Quick Guide

  • Fish oil contains concentrated amounts of EPA and DHA

  • Omega-3s are anti-inflammatory, omega-6s are pro-inflammatory

  • Fish, fish oil, and omega-3s have been shown to reduce the risk of cardiovascular disease events, however, recent studies are trending towards no benefit in terms of fish oil supplementation

  • Most fish oil supplements are highly oxidized, and lower in EPA and DHA than what is claimed on the label

  • Real fish contains more nutrients than fish oil

  • For best results, eat real fish a couple times a week


What is Fish Oil?

Fish oil is just that, its concentrated oil from pressed and processed from fish. Fish oil is rich in the omega-3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). If we compare it to the real thing, fish is a better option because it not only contains all of the omega-3s you need, but it’s also nutrient dense. Fatty fish like salmon contains vitamin D, vitamin B12, selenium, potassium, and magnesium. Some of these nutrients are generally under consumed, especially in the US. (100g of Atlantic wild salmon provides 1.429 g of DHA, 0.411 g of EPA, 25 g of high bioavailable protein, 3 μg of B12, 46 gof selenium, over 600 mg of potassium (more than a banana), and 37 mg of magnesium.) Fish oil doesn’t contain any of these nutrients, unless you buy cod liver oil. Cod liver oil does contain vitamin D and vitamin A, but it’s lower in EPA and DHA. (3)


Essential Fatty Acids

There are two essential fatty acids that we have to consume because our bodies can’t synthesize them. They are linoleic acid (LA), better known as omega-6, and alpha-linolenic acid (ALA), better known as omega-3.  We must consume these because we can’t make them with our own enzymes. (4)

LA rich foods are chicken, eggs, nuts, seeds, and various oils like cottonseed, sunflower, and vegetable oils. ALA rich foods are green leafy vegetables, flax, chia seeds, and walnuts. When we consume ALA, we can actually make EPA and DHA from it. That being said, ALA is converted relatively poorly to EPA and DHA. Fish and fish oil supplements are neat in that they are high in EPA and DHA, so our bodies don’t need to convert anything.  This is a good thing.  However, it’s worth noting that ALA is the actual essential fatty acid, and EPA and DHA are not essential fatty acids, technically speaking. Since the conversion rate is slow from ALA to EPA and DHA, it is recommended to consume EPA and DHA from sources like fatty fish. Also, when we talk about omega-3s, we are talking about a category of fatty acids. ALA, EPA, and DHA are all omega-3s. (5)



Omega-3s and Omega-6s can influence inflammation. When we talk about inflammation in health care, we are generally talking about “bad” or pathological inflammation. Inflammation itself isn’t necessarily bad. Inflammation is what heals our injuries like paper cuts, protects us, and helps to fight against infections. Inflammation becomes bad when it’s chronic and not needed. If out of control, excessive, and not regulated properly, it can damage healthy tissue. A bad case of inflammation is inflammatory bowel disease.

A key mechanism by how omega-3s and omega-6s influence inflammation is through the generation of eicosanoids, which mediate and regulate inflammation and immunity. Prostaglandins, thromboxanes, and leukotrienes are all different types of eicosanoids. In general, the eicosanoids derived from omega-3s are anti-inflammatory, whereas the eicosanoids derived from omega-6s are pro-inflammatory. When we begin to eat too much omega-6s and not enough omega-3s, out body can be in a more pro-inflammatory state. (6)


The Benefits of Fish Oil

Omega-3s from fish oil and fish are touted for their potential to be anti-inflammatory, anti-platelet, anti-thrombotic, and they also lower triglycerides. These beneficial effects are particularly important for those with or at risk of developing cardiovascular disease, which is why most of the research on fish oil is geared towards this condition. Even when subjects take a supplement instead of eating fish, they still have improvements in cardiovascular disease events. (7)

A 2013 meta-analysis of randomized, placebo controlled trials found that patients with cardiovascular disease who supplemented with at least 1 g of omega-3s per day for at least 1 year reduced the risk of cardiac death, sudden death, and myocardial infarction. (8)

A recent meta-analysis from 2016 of 19 observational studies found that higher levels of omega-3s in the body are associated with a lower risk of dying from coronary heart disease. (9)  Higher levels of circulating omega-3s can be established by consuming fish oil, but also by eating real fish and sources of ALA.


Fish Oil Might Not Be That Good

There’s definitely a lot of discrepancy between what a supplement label says it contains, and what the supplement actually contains. A study looking at 32 fish oil supplements from New Zealand found that only 3 of them contained quantities of EPA and DHA that were claimed, and most them contained less than 67% of what was claimed. The scary part is that most of the fish oil supplements were above the threshold and safety limits of oxidation, and only 8% met the international recommendations of oxidation values. When EPA and DHA are oxidized, they become a different fatty acid. Consuming oxidized fish oils has also been shown to be harmful in animal studies, but no long term studies on humans have been observed. (10) Basically, you’re buying highly oxidized, unhealthy, and lower levels of EPA/DHA supplements. Although antioxidants that are added to fish oils do reduce the levels of oxidation, they do not prevent it entirely. Some fish oil products contain additives to make them taste better, which can actually increase oxidation. (11) Findings from studies looking at fish oils from other parts of the world are consistent with this, including in North America. (12)

In terms of fish oil supplementation on improving cardiovascular disease, a lot of the new research is pointing towards it not helping much. A meta-analysis from 2012 of 14 randomized, double-blind, placebo-controlled trials, found insufficient evidence of beneficial effects from omega-3 supplementation against cardiovascular events. (13)

A more recent meta-analysis from 2016 of eight randomized controlled trials along with two other meta-analyses also came to the conclusion that there is a lack of evidence to support supplementation of omega-3s for cardiovascular disease prevention. (14) One study actually found supplementation with a blend of krill and salmon oil to be harmful by decreasing insulin sensitivity (increasing insulin resistance). (15) This means that supplementation with fish oil could potentially increase the risk of diabetes and cardiovascular disease.



When I see mixed results like this, I believe that omega-3s might have some benefit in some people, but not everyone. Also, there may be other factors that need to be considered, such as what are the subjects actually eating, what is the source of the omega-3s, are they exercising, etc.  These are randomized controlled trials, but still, the results are mixed, so there’s likely another factor or something we are missing. There is still evidence supporting a lower risk of cardiovascular disease with eating healthy and consuming at least two serving of fatty fish a week. It’s likely that fish oil does not provide the same benefits as eating an actual fish. The Academy of Nutrition and Dietetics recommends two or more servings of fatty fish per week, which should provide the body with an average of at least 500 mg of EPA and DHA per day. The FDA approves that 2,000 mg per day of EPA plus DHA from a supplement is safe, but don’t exceed that amount. (16) I recommend eating the real thing, and only take fish oil supplements if you can’t get fatty fish in your diet.

Disclaimer: Always check with your doctor before trying any of the supplements or diet strategies discussed.