My mum and dad are troopers. Every morning, they down a tablespoon of fish oil in an effort to stave off old age and dry rot. And they do it without any obvious signs that swallowing a few millilitres of fishy oily stinky liquid is probably the worst way to start a morning. Clearly, they’re from a more stoic generation.

Since fish oils – or more accurately, the omega-3 long chain polyunsaturated fatty acids (n-3 PUFAs) in fish oils – have been linked to cognitive performance, the “lubricate the ol’ brainbox!” idea behind getting the stuff into your system has a lot of appeal. Especially when you’re trying to achieve literary perfection in your blog articles (disclaimer: no fish oil was consumed during the writing of this article). But, for some of us, the idea of choking it down in its liquid form is overwhelmingly repulsive.

Enter: fish oil capsules. On the surface, the perfect solution! The fish oil stays safely trapped in its hard shell until it passes down through the stomach and into the upper intestine. Once there, the capsule degrades enough to allow the brain lube to erupt.

There’s just one problem. New research led by Benjamin Albert at the University of Auckland in New Zealand shows that the quality of over-the-counter fish oil capsules is pretty rubbish. Albert and his team bought 32 different brands of fish oil capsules, and measured them for levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), supposedly the “good” n-3 PUFAs responsible for brain gains. They found that 69% (29/32) had lower levels of EPA and DHA than the companies claimed on the label (see the graph below). As an interesting side note, the more expensive capsules were more accurately labelled for EPA and DHA levels.

To achieve such lower-than-advertised levels of EPA and DHA, either the freshly isolated fish oil had lower concentrations to begin with, or the oil within the capsule degraded over time. Both EPA and DHA are prone to oxidation, and break down to form a soup of peroxides, aldehydes and ketones. In fact, fish oil supplement manufacturers typically add anti-oxidants into their capsules to slow this process.

When the New Zealand team tested oxidation values across fish oil capsules, 92% exceeded one or more international recommendations. But older capsules that had been on the shelves for longer didn’t show any difference in oxidation values compared to newer ones. This suggests that there were lower levels of active EPA and DHA at the very beginning of the manufacturing process, and that many companies may be failing to test their individual batches of fish oil.

What might such oxidation values mean for the consumer? While some studies indicate that oxidation breakdown products may in fact be responsible for the anti-inflammatory benefits of fish oil, at high experimental doses, they can cause organ toxicity, stunted growth and accelerated atherosclerosis. The overall effect (if any) of consuming products with high oxidation values on health is still very unclear; hence, levels in fish oil capsules are subject to recommendations based on palatability rather than legal requirements based on safety.

If this research is representative of the global market, consumers have a 1 in 11 chance of buying fish oil capsules that contain robust levels of EPA and DHA. These odds might improve a little if they stick to high-end brands. All in all, until better standards and regulations hit the fish oil supplement market, it’s probably a good idea to look for your brain boost elsewhere.

Albert, B., Derraik, J., Cameron-Smith, D., Hofman, P., Tumanov, S., Villas-Boas, S., Garg, M., & Cutfield, W. (2015). Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA Scientific Reports, 5 DOI: 10.1038/srep07928