Some observational studies show that increased consumption of fish oils rich in omega-3 long-chain polyunsaturated fatty acids (omega-3 PUFA) may reduce the chance of developing dementia.Some do not show any benefit .
PUFAs are postulated to have some role in brain functioning. 1. key component of membrane phospholipids in the brain may help maintain membrane integrity and neuronal function. 2. The oxidative products of PUFAs act as key cellular mediators of inflammation, allergy and immunity, oxidative stress, vascular responses and thrombosis and may thereby influence risk especially of vascular dementia (Uauy 2006) 3. DHA (docosahexaenoic acid ) may modify the expression of genes that regulate a variety of biological functions potentially important for cognitive health, including neurogenesis and neuronal function (Rojas 2003).
Do they do good to those who take it?
Sydenham E, Dangour AD and Lim W-S (The Cochrane Library 2012, Issue 9 ) did a meta analysis to answer this question. They looked in to new cases of dementia diagnosed during the study period where cognitively healthy 60 plus participants were given omega 3 PUFA fish oils. They included 3 methodologically sound RCTs with a total of 3536 participants. Participants in both the intervention and control groups experienced little or no cognitive decline during the studies.tests of cognitive functions showed no difference between groups.Apart from minor GI problems there were no side effects.
The review concludes that adding fish oils is of no benefit for cognitive function . How ever, we do not know whether the outcome will be different among those who have low dietary PUFAs. The longest duration of study was 40 months only. So it is not whether longer duration will have any benefit.
Studies included in the analysis are Van de Rest 2008, Geleijnse 2011 and Dangour 2010.
Please see Sydenham E, Dangour AD and Lim W-S (The Cochrane Library 2012, Issue 9 for further details.