Question & Answer

Does taking omega 3 or omega 6 fatty acids, either as supplements or through diet, improve brain health or cognitive function? If so what 'dose' is needed.

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The Evidence

  • Cognition is a combination of processes in the brain that includes the ability to learn, remember, and make judgments. Cognitive decline is the experience of worsening or more frequent confusion or memory loss and this can be a normal part of ageing. However, sometimes cognitive decline is associated with dementia. Dementia involves disturbances of memory, thinking, orientation, perception and behaviour, which are often severe enough to affect the ability to perform everyday activities.
  • Omega-3 and/or Omega-6 supplements are sometimes suggested to improve cognitive function.
  • We looked for studies to explore whether taking Omega-3 and/or Omega-6 supplements helps with cognitive function.
  • We found four good-quality systematic reviews on the effect of Omega-3 supplements in cognitive decline and dementia.
    • The first systematic review looked at 3 studies of people living with dementia and found no convincing evidence that Omega-3 supplements help to treat dementia.
    • The second systematic review looked at 3 studies of people aged 60 years or older without dementia or cognitive impairment. This review found no benefit from Omega-3 supplements on cognitive function in these healthy older people.
    • The third systematic review looked at 13 studies of people without dementia or cognitive impairment and found that Omega-3 supplements do not alter cognitive performance.
    • The fourth systematic review looked at the effect of Omega-3 throughout the life span from infancy to old age. While there was no improvement in cognitive performance in children, adults, or the elderly, the review found that Omega-3 supplements might help cognitive development in infants.
  • Overall, the available evidence on the use of Omega-3 supplements in improving cognitive function shows no beneficial effect, apart from cognitive development in infants.  There was no high-quality research evaluating the effects of Omega-6 supplements on cognitive function.

 Guidelines and recommendations

  • We searched several national and international organisations including WHO, CDC, ECDC, HSE, and HSPC for related guidelines and recommendations.
  • We did not find any guidelines or recommendations on the use of Omega-3 and/or Omega-6 supplements in improving cognitive function.

Things to Remember

  • Just because one study shows that people who got a treatment did better or worse than those who did not, does not mean it’s the final answer.
  • If someone gets better after a treatment, it does not necessarily or always mean that the treatment made them better.
  • We can rarely be 100% certain about any claim.


  • Lead Researcher: Dr. KM Saif-Ur-Rahman, Senior Research Methodologist, Evidence Synthesis Ireland and Cochrane Ireland, College of Medicine, Nursing and Health Sciences, University of Galway
  • Reviewed by: Dr. Paula Byrne, Senior post-doctoral researcher, iHealthFacts, Evidence Synthesis Ireland and Cochrane Ireland, College of Medicine, Nursing and Health Sciences, University of Galway.
  • Topic advisor: Dr. Sinéad Lydon, Associate Professor, Discipline of General Practice, School of Medicine, University of Galway.
  • Public and Patient advisor: Deirdre Mac Loughlin, Public and Patient Involvement in research (PPI) advisor, PPI Ignite, University of Galway.
  • Journalist Advisor: Dr. Claire O’Connell, PhD in cell biology, Masters in Science Communication. Contributor to The Irish Times, writing about health, science and innovation.

Conflict of Interest Statement: The authors have no financial or other conflicts of interest for this health claim summary.