Does omega-3 fatty acids protect against cognitive decline in older adults? The debate is still on.
Omega-3 fatty acids are essential fatty acids that play a crucial role in brain function and visual acuity. Unfortunately, the body can't make them. They have to be derived from the food such as fatty fish (salmon, tuna, etc.), seafood including algae and krill, flaxseed, soy and nut oils.
AdvertisementAlthough Omega-3 fatty acids have become popular because they may reduce heart disease, a number of studies have found increased dietary consumption of omega-3 (n-3) fatty acid - DHA (docosahexaenoic acid) to be useful in protecting against cognitive decline, including Alzheimer's disease and dementia, in elderly people.
However, the results of the studies are not entirely consistent. So far only two randomized, controlled trials have assessed the effect of n-3 LC PUFA supplementation on the cognitive function in the older population. Out of this only one study could establish a link between omega-3 long-chain polyunsaturated fatty acids and cognitive decline. According to the 2005 study published in the Archives of Neurology 'there was little evidence that the omega-3 polyunsaturated fatty acids were associated with cognitive change'. But they concluded that 'fish consumption may be associated with slower cognitive decline with age'. They recommended further studies to determine 'whether fat composition is the relevant dietary constituent'. On the other hand, a Canadian study published in the Journal of Alzheimer's disease did not support the hypothesis that n-3 LC PUFAs (omega-3 long chain polyunsaturated fatty acids) play a protective role in cognitive function and dementiadespite adjusting the results for age, sex, education, smoking, alcohol intake, BMI, history of cardiovascular disease and most importantly apolipoprotein E epsilon4 (APOE epsilon4) gene.
The difference in results may be because of the differences in design and methods of studies, but scientists are finding evidence that the genetic make-up (especially the effect of the gene APOE epsilon4) and physiological wellbeing of the subjects also significantly influence the study outcome.
Thus, the benefits of n-3 LC PUFA supplementation on cognitive function in older normal people still remains unclear. So, a controlled trial to investigate the potential of n-3 LC PUFA, with special focus on APOE epsilon4 gene, as moderating factor to slow cognitive decline in cognitively healthy older adults has been undertaken by Vanessa Danthiir and her colleagues from Australia. The researchers hypothesized that 'over 18 months, the n-3 LC PUFA supplementation group would show slower cognitive decline than the control group'. This methodology study paper has been published in the Nutrition Journal.
The study dose was 1720mg DHA and 600mg EPA (another n-3 LC PUFA -eicosapentaenoic acid) daily. Each capsule contained 430mg DHA and 150mg EPA. Participants were administered four capsules a day, two in the morning and two in the evening. The total n-3 LC PUFAs in the daily supplement were equivalent to approximately 150g of salmon. Other factors including nutritional intervention were also considered and closely monitored.
Participants were scheduled one visit to the laboratory for assessment, every 6 months, for 18 months. For each assessment visit, participants attended the clinic after an overnight fast, and a blood sample and physical measurements (height, weight, and blood pressure) were undertaken. Carotenoids, folate, and vitamin B12 - all associated with cognitive functioning in the elderly - were assessed.
Apolipoprotein E (ApoE) genotyping was also conducted in order to examine any differential effect of treatment due to APOE-epsilon4 allele. Blood was taken at the second and third assessment points in order to assess 'erythrocyte membrane fatty acid composition' at each time point. The researchers said, 'n-3 LC PUFA status will be used to assess compliance/uptake post-hoc and we will also assess whether changes in n-3 LC PUFA status are associated with any changes on our outcomes'.
This paper is on methodology and protocol of the study undertaken by the researchers where they will be looking into the outcome measures such as:
• Primary outcome - Rate of change in cognitive performance
• Secondary outcome - Change in perceived health status, depressive symptoms, positive and negative affect, life satisfaction, self-reported cognitive functioning, and functional capacity; blood pressure; biomarkers of glucose, glycated haemoglobin, triglycerides, total cholesterol, HDL, LDL, homocysteine, CRP, MDA, and telomere length
Since there is no definitive evidence of cognitive domains that could change by n-3 LC PUFAs, comprehensive assessment was done on all domains that might benefit from a nutritional intervention.
In conclusion the researchers stated, 'This is one of the few trials to date to examine the impact of n-3 LC PUFA supplementation on cognitive decline in cognitively healthy older adults. Advantages of the current study are the comprehensive assessment of cognitive functioning and the multiple measurement points, which allow for assessment of an intervention effect on a trajectory, rather than effects at a specific time point. The significance for society could be wide-ranging if such an available and inexpensive dietary treatment has the possibility to safely reduce cognitive decline in ageing, given the links between cognitive functioning and the societal and personal burden of dependency and decreased quality of life in older age'.
Danthiir,Vanessa et al. The Older People, Omega-3, and Cognitive Health (EPOCH) trial design and methodology: A randomised, double-blind, controlled trial investigating the effect of long-chain omega-3 fatty acids on cognitive ageing and wellbeing in cognitively healthy older adults. Nutrition Journal 2011, 10:117 doi:10.1186/1475-2891-10-117 http://www.nutritionj.com/content/pdf/1475-2891-10-117.pdf
• Morris MC, Evans DA, Tangney CC, Bienias JL, Wilson RS. Fish consumption and cognitive decline with age in a large community study. Arch Neurol. 2005 Dec;62(12):1849-53. http://www.ncbi.nlm.nih.gov/pubmed/16216930
• Laurin D, Verreault R, Lindsay J, Dewailly E, Holub BJ. Omega-3 fatty acids and risk of cognitive impairment and dementia. J Alzheimers Dis. 2003 Aug;5(4):315-22. http://www.ncbi.nlm.nih.gov/pubmed/14624027