Fish oil

Omega-3 and supplements

7 min readOct 19, 2021
Photo by Brandon on Unsplash

The multi-billion dollar supplement industry might have peaked (in the UK at least). It has been a formidably effective industry, selling the promise of better health to the worried healthy.

One supplement is holding out though — fish oil. Coming from a natural source (presumably fish) and with a beneficial nutrient (long-chain omega-3 fatty acids), it has been an easy sell. In fact, it is widely oversold, with claims for health-benefits that can invite comparison to the snake oils of a previous era.

Nonetheless, it is undeniable that these fatty acids are important to our health and that our bodies cannot synthesise them in sufficient amounts for our needs, so they must be consumed in our diet. Just as some vitamins are ‘essential’, so are some fatty acids.

What is an omega-3 fatty acid?

Fatty acids are simple chains of carbon atoms. Each carbon bonds to the carbon before and after it in the chain, as well as to 2 hydrogen atoms. Such an arrangement is a saturated fatty acid.

If two adjacent carbon atoms each release one of their hydrogens and use the loose ends to form another bond with each other (i.e. they double-bond) then the fatty acid is unsaturated. If this happens once in the chain, it is mono-unsaturated. If it happens more than once, it is poly-unsaturated.

If the total number of carbons in the chain is greater than 12 it is said to be a long-chain fatty acid.

Finally, if the last carbon with a double bond occurs 3 carbons in from the end of the chain, it is said to be an omega-3 (⍵-3) fatty acid (omega being the last letter in the Greek alphabet, so ‘3 in from the end’). Fish oil contains long-chain poly-unsaturated ⍵-3 fatty acids.

You might come across a notation like 20:5 (n-3) in some nutritional analyses. This means the fatty acid is 20 carbons long, has 5 double bonds and is an ⍵-3. This is actually one of the four main long-chain ⍵-3s (EPA) that are of interest.

There is also a matching set of long-chain poly-unsaturated omega-6 (⍵-6) fatty acids (meaning the last carbon with a double bond occurs 6 carbons from the end). Also essential.

What is our dietary balance for ⍵-3s and ⍵-6s?

It is estimated that our ancestors probably had a ⍵-3 to ⍵-6 ratio in their diets that was between 1:1 and 1:4. In our modern diet, this ratio has been significantly distorted in favour of ⍵-6. I have seen estimates as high as 1:30.

Why might this balance matter?

Apart from contributing to the the function of multiple body systems (eg brain, retina, skin), the ⍵-3s and ⍵-6s regulate inflammation in complementary ways: ⍵-3s are anti-inflammatory whereas the ⍵-6s are pro-inflammatory. So, they are meant to be in balance. Currently, we have a massive imbalance favouring ⍵-6 (pro-inflammation). There is ongoing interest in the implications for our health.

Why do we even need pro-inflammatory fatty acids?

Managing inflammation is an important part of our physiology. For example, the immune system responds to injury by initiating an inflammatory response to kill damaged cells (or invading cells) before eliminating them and initiating repair mechanisms.

However, uncontrolled inflammatory mechanisms may also be associated with the modern ‘disorders of civilisation’ (eg obesity, type-2 diabetes, arthritis, heart disease, cancer).

Why does our diet favour ⍵-6?

Beacuse we have followed dietary advice. By far the greatest source of ⍵-6s are vegetable oils, margarine and vegetable shortening. The switch from animal fats (our hereditary fat source for aeons) to ultra-processed vegetable oils (only relatively-recently available) is the reason.

We have been urged to give up animal fats because they can raise cholesterol and perhaps increase heart disease (the evidence does not support this though). But, the change to vegetable oils (and excessive ⍵-6 intake) carries the potential for inflammatory up-regulation that could also have adverse effects (e.g. increasing the risk of heart disease, ironically). These subtleties are not spoken of in orthodox dietary advice, even though they are clearly important.

Is this why we need to increase our ⍵-3 intake?

Perhaps. But that only addresses half the problem — reducing excessive ⍵-6 is the other (more important) half. It would help to relax dietary advice on animal fats. I don’t expect we will see that for a long time though. In the meantime, we will just have to remain unhealthy (or ignore the orthodoxy).

Supplements vs. real fish?

Supplements lack the diversity of fish oil consumed with fish. Fish comes with co-nutrients that may influence uptake or be involved in multiple metabolic pathways together with the fatty acids. Eating fish means we don’t eat something else less healthy and take a capsule to compensate.

Fish oil supplements (like other supplements) are not considered to be a medicine — they are not officially regulated. Manufacturers are not required to register their product with the FDA (or equivalent agency), nor are they required to provide proof to an agency that their product contains the ingredients or doses on the label. Apart from misleading-advertising laws, there is nothing else to regulate their contents. Consumers are not in a position to perform mass spectroscopy to find out either. When subject to laboratory analysis, significant deviations from the labels can be found.

Long-chain poly-unsaturated oils such as fish oil are unstable and prone to oxidation that produces damaging free-radicals. We can tell when this has happened in fish because is smells rancid and we don’t eat it. The extent to which this might have happened in a capsule is not apparent, and also not apparent when swallowed. Some manufacturers add vitamin E (an antioxidant) to prolong shelf life and delay rancidity. It is rare to detect significant rancidity in independent analyses of off-the-shelf capsules. However, it is common to find signs of oxidative precursors to free radicals (peroxides). Whether this matters (or also occurs in older but still edible fish), I am not sure. Peroxides have no nutritional value.

Inuit diet

The importance of ⍵-3 fatty acids got a signifiant boost in the early days when it was found that native Inuits had a diet high in fat but suffered little heart disease. The ⍵-3 fatty acids in seal meat and blubber were hailed as the reason, and dietary advice consolidated. However, western dietary organisations were not going to promote blubber (even assuming we had access to it), so they sought (and found) an alternative — fatty fish such as salmon. However, seal meat/blubber has a different ⍵-3 fatty acid profile to oily fish.

Dietary sources besides seal blubber?

Wild game (such as venison, kangaroo) and grass-fed beef and lamb. Human breast milk as well, highlighting its dietary significance.

However, if beef/lamb comes from grain-fed animals, then there is virtually no ⍵-3 in the fat or meat. This subtelty of provenance may not be apparent at point-of-sale.

It also explans why nutritional analysis of beef from Australian laboratories gives high ⍵-3 readings, wheres the equivalent analysis from US laboratories gives low ⍵-3 readings. It turns out that at the time these analyses were performed, most Australian beef was grass-fed while most US beef was grain-fed. Australian beef is currently promoted as being mostly grass-fed.

A diverse diet that includes grass fed animals and oily fish will give a nutritional balance across all three of the main ⍵-3 fatty acids.

Is supplementation a precaution anyway?

I have drawn attention to the subtleties and complexities underlying the health science of ⍵-3. It is for the individual to decide if supplementation is advisable. Currently, there is no convincing scientific evidence that supplementation is effective in preventing any disease or disorder in healthy individuals. It is also not protective in people with risk factors for heart disease.

You may not have a choice though. Adding fish oil supplements to grain-fed beef is under investigation. About half of the fish oil currently manufactured is already used as feed for farmed salmon. Marine fish oil is a dwindling resource and its use compromises the environmental credentials of farmed salmon. About half the fish oil may be replaced by vegetable oils (potentially disturbing the ⍵-3/6 balance).

For us humans, manufacturers are already supplementing (fortifying) their products with ⍵-3s to get coveted ‘ticks’ from nutritional agencies or to drive consumer purchase. Some examples are margarine, oils, milk, yogurt, cereal, chocolate, baked goods and many more — its a rapidly growing list. We are being experimented on, again.


I expect that people who eat diversely can dispose of their fish oil capsules. Maybe ‘touch wood’ once a day instead.

PS: Some things I left out.

  1. There are also omega-9 fatty acids. Less in known about them but they are sure to be important.
  2. Eating a variety of fish (oily and non-oily) does not result in a detectable increase in serum ⍵-3, but is likely to be heathy for other reasons.
  3. Oily fish don’t synthesise ⍵-3, they get it from phytoplankton that they either either eat directly or that is in their food chain.
  4. Most freshwater fish are low in ⍵-3.
  5. Fish oil in supplements comes from unspecified fish offcuts and also from caught fish. The sustainability of the caught fish component is uncertain.
  6. Fish oil won’t ‘oil your joints‘. The synovial fluid that lubricates joints is a protein gel, not an oil. It’s like egg white (the ‘ovia’ in the name means egg). Cartilage is a kind of firm sponge that holds the synovial fluid. When the joint is placed under pressure, fluid is squeezed out of the cartilage and lubricates the joint. It is self-adjusting, the more pressure the joint is under, the more lubricating gel is released.
  7. Krill oil seems popular too. It is disturbing to think what might happen if krill, at the beginning of the marine food chain, became over-harvested for the dubious purpose of meeting (or creating) demand for krill oil capsules.
  8. Fish fat is an oil (i.e. liquid at room temperature) because fish are cold-blooded and their fat must remain fluid at low ocean temperatures (down to 0C in some cases). Animal fat is fluid while it’s inside the animal (warm blooded) and only solidifies into a fat when brought down to room temperature or refrigerated. It may feel solid in our bodies, but that is because of the cellular structures holding it.




Science of cooking, eating and health. Retired neuroscientist.