The Evidence

There is compelling evidence that supplementing omega-3 helps protects against cognitive decline. A 2023 study in the American Journal of Clinical Nutrition of over 100,000 people showing that an increased intake of omega-3, either from diet or supplements, or having a higher omega-3 blood level, cuts the risk for dementia by a fifth (20%).[i]  A 2023 study, by psychologists at the Linda Loma University in California and published in the journal Brain Sciences[ii], have found that the higher a person’s omega-3 index was in their blood, the more white matter there was in their brain, and the better they performed on cognitive tests that predict less risk for dementia. A 2022 study using data from the UK BioBank reports a 9% lower risk of all-cause dementia in those using fish oil supplements.[iii]

Dr Veronica Witte and colleagues from the Department of Neurology at the Medical University in Berlin, decided to find out by giving 65 healthy 50-75 year olds 2.2g a day of omega 3 fish oils a day for 26 weeks and seeing what happened to their brains.[iv] Not only did they get some significant cognitive improvements, with better memory, more flexible thinking and ability to focus, but their brains also got a physical upgrade with an increase in grey matter volume and more white matter integrity, which indicates better wiring. In just six weeks you could see evidence of a brain upgrade! Also, the higher their blood levels of omega-3 the greater were the improvements.

Philippa Jackson, Associate Professor of Biological Psychology and the Associate Director of the Brain, Performance and Nutrition Research Centre in Northumbria University in Newcastle, devised a study to find out if similar effects could be seen in younger people. She gave healthy 18 to 29 years old either 1 or 2 grams of DHA, not only looking at the effects on cognitive tasks, but also what happens in the brain during cognitive tasks. She found both doses increased brain function by improving blood brain flow. Her research suggests studies which administer less than 2 grams of omega-3 per day, which would give you in the order of 1g of DHA, are unlikely to produce clinically relevant cognitive performance enhancements in healthy younger people.

How Much?

All of this evidence broadly concurs with the decades of research by Captain Joe Hibbeln MD, advisor to the US National Institutes of Health, concluding that the majority are protected from chronic diseases, not just brain disease, with an intake of 750mg a day of omega-3 EPA, DHA and DPA.[v]  That is the ADDITION of the levels of these three essential fatty acids that you’ll find listed on the back of a supplement.

DHA is the omega-3 fat that builds the brain and the body can synthesise it from EPA or DHA. Most fish oils are roughly 50/50 EPA and DHA. Some hame more EPA (important for mood) others a higher proportion of DHA (a structural brain essential).

Looked at from all these different points of view an intake of 2 grams of omega-3 from fish or fish oil, providing at least 750mg of DHA (and about the same amount of EPA), and at least a total of EPA+DHA of over 1,000mg, seems to be optimal. More may be better for those suffering from omega-3 related health problems.

If you are eating fish three times a week, with at least two servings of oily fish, your contribution from diet is likely to average out at 215mg of DHA a day. (A serving of mackerel or salmon, for example, will give you over 2 grams of omega-3 fats and at least 750mg of DHA).

So, if we assume you will achieve at least 200mg of DHA from diet (you could get more if you eat more fish or less if you don’t eat fish at all), then it is wise to supplement in the order of 500mg of DHA a day, which will probably give you an equivalent amount of EPA.

The following supplements give 500mg of DHA, or more, in one or two capsules and at least 750mg of combined DHA+DPA+EPA.


[i] Wei BZ, Li L, Dong CW, Tan CC; Alzheimer’s Disease Neuroimaging Initiative; Xu W. The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline: Evidence from Prospective Cohort Studies of Supplementation, Dietary Intake, and Blood Markers. Am J Clin Nutr. 2023 Jun;117(6):1096-1109. doi: 10.1016/j.ajcnut.2023.04.001. Epub 2023 Apr 5. PMID: 37028557; PMCID: PMC10447496.

[ii] Loong, S.; Barnes, S.; Gatto, N.M.; Chowdhury, S.; Lee, G.J. Omega-3 Fatty Acids, Cognition, and Brain Volume in Older Adults. Brain Sci.2023,13,1278. 10.3390/brainsci13091278

[iii] Huang Y, Deng Y, Zhang P, Lin J, Guo D, Yang L, Liu D, Xu B, Huang C and Zhang H (2022) Associations
of fish oil supplementation with incident dementia: Evidence from the UK Biobank cohort study.
Front. Neurosci. 16:910977. doi: 10.3389/fnins.2022.910977

[iv] Witte AV, Kerti L, Hermannstädter HM, Fiebach JB, Schreiber SJ, Schuchardt JP, Hahn A, Flöel A. Long-chain omega-3 fatty acids improve brain function and structure in older adults. Cereb Cortex. 2014 Nov;24(11):3059-68. doi: 10.1093/cercor/bht163. Epub 2013 Jun 24. PMID: 23796946.

[v] Hibbeln JR, Nieminen LR, Blasbalg TL, Riggs JA, Lands WE. Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity. Am J Clin Nutr. 2006 Jun;83(6 Suppl):1483S-1493S. doi: 10.1093/ajcn/83.6.1483S. PMID: 16841858.