Omega-3 does NOT improve cognitive abilities, memory, and brain function?

Question

Omega-3 is generally found in foods like walnuts, fish, etc. It is generally believed that omega-3 promote cognitive health, memory, and brain function. However, I am quite shocked to read a recent article which consisted of a study that was cited in it. This study claims that omega-3 does NOT improve cognitive abilities, memory, or brain function as commonly believed by several health experts. The study was published on well-known news service called "CBS News". The link to this study can be found here:-

https://www.cbsnews.com/news/omega-3-fatty-acids-wont-help-your-memory-study-finds/

Another study which was also published at the CBS News also found that consuming Omega-3 supplements provided no mental or cognitive benefit:-

https://www.cbsnews.com/news/taking-omega-3-supplements-may-provide-no-mental-or-cognitive-benefit/

THE STUDY CONTRADICTION

These studies contradict other studies that claim that omega-3 might provide benefits when it comes to cognitive abilities or memory. Some of these studies are here:-

https://www.forbes.com/sites/daviddisalvo/2012/10/29/new-study-shows-that-omega-3-supplements-can-boost-memory-in-young-adults/#618d53dc91ab

https://universityhealthnews.com/daily/memory/omega-3-dha-supplement-proven-to-boost-brain-power/

https://www.medicalnewstoday.com/articles/252198.php

See consumption of walnut and improvement of brain memory:-

https://www.huffingtonpost.com/2015/01/22/walnuts-boost-memory-study_n_6525316.html

NOTE: These studies contradict other studies that claim that consumption of omega-3 can lead to improvement in cognitive functionality and memory, and one may argue that the difference between these two studies is that one study was conducted on older adults, while the other one was conducted on young adults and we may conclude that omega-3 works in younger adults but not in older adults. However, this does not explain why the age factor would influence the effectiveness of omega-3 on memory or cognitive health. Could someone provide some insight? Thanks.

Answer 1

Individual studies often contradict each other. Systematic reviews of studies can at least filter out low-quality studies, so they may show more realistic picture.

In short: Omega-3 fatty acids (fish oil supplements) may have a slight beneficial effect on cognition in those who are omega-3 deficient but not in those with normal omega-3 levels.

1. PubMed, 2012

The available trials showed no benefit of omega-3 PUFA supplementation on cognitive function in cognitively healthy older people.

2. PubMed, 2015

There is marginal evidence that n-3 PUFA supplementation [fish oil containing EPA and DHA] effects cognition in those who are n-3 PUFA deficient. However, there is no evidence of an effect in the general population or those with neurodevelopmental disorders.

3. Cochrane, 2016

...we found no evidence for either benefit or harm from omega-3 PUFA supplements in people with mild to moderate Alzheimer's disease.

4. PubMed, 2018

Current evidence indicates that n-3 LC-PUFAs administered during pregnancy or breastfeeding have no effect on the skills or cognitive development of children in later stages of development. Evidence regarding the improvement of cognitive function during childhood and youth or in attention deficit/hyperactivity disorder is inconclusive. Moreover, it is still unclear if n-3 LC-PUFAs can improve cognitive development or prevent cognitive decline in young or older adults.