Omega-3s and cognition: dosage matters!

By Adam Ismail

- Last updated on GMT

Newsweek wrote “Omega-3 Supplements Are a Waste of Money.” Well, maybe low-dose versions are...
Newsweek wrote “Omega-3 Supplements Are a Waste of Money.” Well, maybe low-dose versions are...

Related tags Cognitive function Omega-3 fatty acid Fatty acid

Yet another study questioning omega-3 efficacy has been picked up by the mainstream press. Why finger the nutrient when the dosage is all wrong? argues Adam Ismail, executive director of the Global Organisation for EPA and DHA Omega-3s (GOED), in this guest article.

Once again the role of omega-3s in health is being called into question, this time in relation to cognitive decline…and once again I feel compelled to try to remind people that we need to look at the overall body of science before drawing conclusions based on a single study.

As many scientists have noted, no single study is perfect…so no definitive conclusions can be drawn from a single study. Yet, this is exactly what is happening in the consumer media in response to a new paper from Chew et al​ on the role of omega-3s and other nutrients in cognitive decline. The results of the study led the authors to conclude, "Contrary to popular belief, we didn't see any benefit of omega-3 supplements for stopping cognitive decline." 

Newsweek​ went so far as to translate this into the declaration, “Omega-3 Supplements Are a Waste of Money.” ​Really, Newsweek? A single study, on a single area of health, means better nutrition is a waste of money? Would they at least change their view if the totality of evidence for that health condition told a different story?

The paper by Chew et al focused on cognitive function though, so let’s look specifically at this area of research. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are both long-chain omega-3s, but they are actually each thought to play different roles in the body, but especially in the neurological system. DHA is the most prominent fatty acid found in the neurological system and is actually part of the structure of your brain and eyes.

One hypothesis is that DHA is really required in sufficient amounts to see effects in cognitive function studies. In fact, one paper​ has shown that DHA consumption leads to greater blood flow and activity in the prefrontal cortex during cognitive tests than EPA, which indicates that DHA is the key player.

Adam Ismail

Another paper​, a recent meta-analysis of randomized, controlled trials by Yurko-Mauro et al, showed that greater than 1g of DHA per day was required to improve some aspects of cognitive function in older adults.

This is important because the media reporting on the paper by Chew et al is that “high dose”​ omega-3s did not slow the rate of cognitive decline in this population, but the supplement that was given to this group only contained 350mg of DHA. One could argue that this is hardly a high dose of DHA since it is less than you would get from a single serving of salmon, but the real question is whether the dose is sufficient for detecting a benefit.

I went to the scientific literature and pulled out all of the papers studying the effects of omega-3s on cognitive function in adults ranging from healthy individuals to having mild Alzheimer’s disease. I excluded studies with subjects that had full-blown Alzheimer’s disease because Chew et al were not trying to see if omega-3s could reverse that horrible disease, they were only trying to establish whether omega-3s played a role in preventing cognitive decline.


I also excluded two small studies with phospholipid omega-3s because there are questions about whether that changes the absorption of EPA and DHA, meaning the doses would not be comparable to the other studies…both found benefits at very low dosages though. Next, I looked at the primary outcomes for each paper, the DHA dosages in each study, and whether the authors concluded that there was a beneficial effect in their studies for those incomes. You can download a table of these papers here​. The results are pretty clear-cut, as the chart below shows. If a cognitive function study does not include a significant amount of DHA, it is not likely to show a benefit.

So why did Dr Chew and her colleagues use such a low dose of DHA, when literature suggests a higher dose is needed? Well, when the design of their study was completed in early 2006, none of this data existed. All of the clinical trials published in this area came out in 2006 or later. Dr Chew and her fellow authors noted in their paper that the dosage could be one of the factors that affected their findings, and while this point made it deep into the text of many stories in the consumer press, the importance of this point was nowhere to be found in the headlines.

This article first appeared here​.

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1 comment

trial that was designed to fail

Posted by Jerome Burne,

Hi I did a post recently on just why the big trial that found omega-3 did nothing to protect cognitive, was seriously flawed and found nothing of the sort.

Here's the beginning of the post:

If you aren’t confused about whether taking omega-3 will keep your brain sharp or is simply a waste of money, you haven’t been paying attention. Last week the media carried reports of a new study that found that taking a gram of fish oil a day didn’t protect elderly people from failing memory and poorer thinking skills.

So is this another bust for supplements and a chance to dismiss omega-3 supplements as ‘codswallop’ and a ‘waste of millions of pounds’?

Absolutely not. Read on before tipping those golden capsules in the bin because far from being another of those supposedly “scientific” studies showing that they are useless, it is actually a very good example of why randomized controlled trials (RCTs) of supplements can be very unreliable and misleading.

I've commented here because I think the way this an similar supplement trials are run is a disgrace and there seems to be a clear pattern to it. Exactly the same type of irrelevant trials have been used to claim that high dose B vitamins have no benefit on slowing cognitive decline - link to details of that post contained in the one on omega-3.

Do get in touch if you are interested.

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