Fish oil – who would have thought something that tastes and smells so awful could evolve into a $2.5 billion business? But are the health benefits real, or is it all a con? Could the supplement, as some have suggested, actually be bad for you?
The Claims
Fish oil supplements are advertised as a way to support heart health, brain function, and vision, while simultaneously lowering the risk of cardiovascular disease. This is a pretty tall order of claims, but nothing compared to the things you might hear from "health influencers" who market the product as everything from a weight loss cure to preventing Alzheimer's. And to be clear, there is not one bit of scientific literature that supports those claims.
The basis for all these fantastical and wondrous properties stems from the high presence of Omega-3 fatty acids in fish oil. Omega-3 is an essential part of a balanced diet and can come from a number of natural sources apart from fatty fish, such as vegetables and nuts. Chances are, you probably already consume the recommended daily intake.
But for those who don’t and choose instead to take a supplement as a top-up, you may be wondering what’s the harm? As it turns out, more than you thought.
Lipid Oxidation
Oxidation, in a sentence or less, refers to the chemical reaction in which a substance reacts and combines with oxygen. Oxidation in lipids (or fats) changes the way the human body metabolises them.
Although there isn’t a huge range of studies that specifically investigate the effects of oxidation in fish oil, there is a general consensus that they interact with the body in a similar way as other, more documented lipid forms. That is, they generate an inflammatory response, increase cholesterol volumes, and potentially generate plaque buildup in the artery walls, all of which, unsurprisingly, have an adverse effect on health.
Now, the bad news is that these fish oil supplements don’t store well for a whole host of reasons. But even more concerning than that is the fact that they are often sold and consumed in an oxidised state. So, if you have ever had a supplement that smelt and looked a little bit off, it probably was.
This isn’t guesstimation either; a study performed in 2015 in Canada tested the oxidation levels of 171 over-the-counter supplements from 49 brands and found that 39% exceeded international voluntary safety recommendations. Other studies conducted in New Zealand and South Africa found this number to be as high as 80%. And it’s really bad news if you are ordering online, as this figure is likely to be higher due to the well-earned reputation of poor storage conditions and product quality.
Heavy Metals
The sea, for the last few decades, has been a dumping ground for global industry, and although some effort has been made to address this, ultimately there remains an ever-increasing amount of pollutants and heavy metals in the marine ecosystem. This toxic content, in trace amounts, makes its way into the fish oil supplements and onto shelves, despite the fact there should have been a purification process.
Now, the average supplement dose isn’t going to have lethal amounts of heavy metals or cause immediate damage, but prolonged exposure to these levels is likely to have long-term health implications. Which is unfortunate, as regularly consuming these supplements is how they’re advertised and expected to be taken.
Increased Risk Of Stroke & Atrial Fibrillation
There is a growing volume of research that indicates that the regular consumption of fish oil supplements by healthy people may increase the risk of cardiovascular disease.
One of the more recent studies conducted in 2024, using data from around 416,000 participants in the UK Biobank study, found an adjusted hazard ratio of 1.13 for the transition from a healthy state to atrial fibrillation, which, as a percentage increase conversion, is 13%. It was also found that healthy regular supplement takers increased their risk of a first-time stroke.
Now, the exact mechanisms of why this occurs have yet to be fully understood; however, research published on this topic at the time of writing supports this trend.
Is There Any Evidence That Fish Oil Supplements Make You More Healthy?
In short, no. Well, nothing that's been found yet. Studies that have previously found a slight reduction in cardiovascular disease and better health are now suspected to have suffered from false causal attribution.
So, for instance, individuals who take multivitamins and other supplements are more likely to be healthier not because they take them but because they are proactively trying to be healthy and are more likely to exercise. The price tag of these supplements also suggests that their consumers are in a better socio-economic position, which increases the likelihood of better healthcare access and a higher-quality diet with less ultra-processed food.
Indeed, the number of double-blind studies conducted over the last two decades involving fish oil supplements and placebos found no evidence of heart-related health benefits, suggesting the benefits may not actually exist.
The TLDR
There are no clear-cut health benefits of consuming fish oil supplements. In fact, they are more likely to do harm if taken over a prolonged period of time by a healthy individual, owing to oxidation, heavy metal content, and the propensity to increase the risk of atrial fibrillation and first-time stroke.
Are they a scam? Most likely. At the very least, the health benefits advertised have no scientific basis, nor indeed do the manufacturers make clear the risk of adverse health effects.
Naturally sourced omega-3, such as the kind found in vegetables, nuts, and fatty fish, is good for you and essential. So, if you are worried about heart health and can’t afford the price tag of regular salmon steaks, incorporate more vegetables in your diet, like spinach.
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