Fish Oil, and Other Sources of Omega 3s

By Steve Midway

Omega 3 fatty acids are a regular health item in the news cycle. One month these ‘fish oil’  supplements are good for lowering cholesterol, the next month they are linked to prostate cancer, and soon there will undoubtedly be another claim. It would take a lot of sleuthing through the primary literature to even get close to a good idea of what omega 3s are and are not good for, but that’s not the objective here. Although we all want to know what can or might improve our health, this week I wanted to take a closer look at what omega 3s are and why are they synonymous with the term “fish oil.”

Fish oil supplements. (

Omega 3 fatty acids refer to any of three main types: ALA, EPA, and DHA. ALA is typically found in plant oils and most notably seeds such as chia, flax, and hemp. EPA and DHA are the two omega 3 fatty acids commonly thought of fish oil, because they are found in the flesh of many cold-water fish species. It should noted, however, that these fish largely do not produce these omega 3s*, but ingest them from marine algae.

*Fish, like humans, can synthesize EPA and DHA from ALA, but at low efficiencies (< 5%). Therefore it makes sense that fish also get omega 3 fatty acids from other souces.

Menhaden are one species harvested for omega 3 production. (

Here at The Fisheries Blog, we have covered omega 3s, such as why they show up in some foods, and some recent research that is showing amazing results with omega 3s. Although it is debatable whether omega 3s are good for a particular malady and/or preventative care, it is clear that some omega 3 fatty acids are required in the human diet, and the medical consensus is to keep the ratio of omega 6 to omega 3 at around 1–4 to 1. Supplements aside, eating more fish is one way to introduce more DHA and EPA to our diets, but many types of grass-fed livestock turn out to be good sources of omega 3 fatty acids as well.

The idea behind all this is that you are what you eat, and animals raised on corn-based feed or other conventional feeds are typically deficient in omega 3s when compared to the same animal raised on their natural diet. For instance, Daley et al. reviewed several studies in which quantities of omega 3s were several times greater in grass-fed varieties of beef versus conventionally-fed cattle. And the same is true for fish oil in fish. Take fish off of their wild diets of plants and other fish (that eat plants that make the omega 3s), and they won’t accumulate the omega 3s to which they have come to be associated. For instance, farm-raised tilapia have some of the lowest levels of omega 3s among all fish, generally attributed to their conventional diet that does not include substantial amounts of the omega 3-rich algae they would otherwise eat.

Tilapia are often very low in omega 3s. (

As we’ve said before, please don’t take any medical or health advice from The Fisheries Blog. But it is clear that omega 3s are necessary to humans, and many of us consider them throughout our day. While fish (meat or flesh) can often be a great source of omega 3 fatty acids, fish across the board are not all high in omega 3s. And nor are all other animals inherently low in omega 3s. Omega 3s are plant-derived, and while fish oil might give you the dose you need, there are certainly other ways to increase your omega 3 consumption.

2 Comments Add yours

  1. Pescarconganas says:

    I’m surprised there was no mention of supporting sustainable harvest of menhaden. Widespread decline due to over harvest for fish oil has caused detriment to other valuable species such as bluefish and striped bass. Those ugly bunkers are the most important fish in Atlantic/Gulf waters!!!

  2. Dean Bowman says:

    “You are what you eat” will come back to haunt humans in some way or another. I saw a documentary that claimed chicken in the late 60’s contained 10 times the Omega 3 that it does now. It seems the degradation of the chickens food source by our farming practices is solely to blame and we are heading down the same path with aquaculture? It would also seem that if our farming/cultivation practices were in order there would be enough omega 3 naturally in our diet and we would not need to pillage the sea to fill the plastic pill bottles we would no longer require with fish essence. Vicious circle ☺

    Greedy, lazy, lack of understanding, global overpopulation – what is the issue and how can we fix it?

    Regardless, we all need to remember “What you eat is what it is because of what it eats”. Conscientious consumer pressure is something we can all exert.

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