By Craig Weatherby
Do diets high in omega-3 fatty acids from fish protect people from cognitive decline and dementia?
Evidence from “observational” studies suggests that they can, but only recently has the strength of this potential protective power been tested in controlled clinical trials.
In observational studies (and other epidemiological studies), researchers compare people’s estimated omega-3 intakes to their brain-health status.
Epidemiological studies can detect statistical correlations between omega-3 intakes and brain health, but they cannot prove them.
Last summer, researchers reviewed the data from three randomized controlled trials of omega-3 supplements considered of high quality.
Each of these trials lasted at least six months and involved participants aged 60 years and over who started out free from dementia or cognitive impairment.
As they wrote, “The [three] available trials showed no benefit of omega-3 supplementation on cognitive function in cognitively healthy older people ...” (Sydenham E et al. 2012)
But we’ve reported positive results from clinical trials using omega-3 supplements, and studies that used blood tests to determine people’s omega-3 levels.
Now, a small trial from Sweden adds a bit more credibility to the idea that supplemental omega-3 fish oil yields real brain anti-aging benefits.
Fish oil trial finds brain and metabolic benefits
This small trial comes from Sweden’s Lund University, and was designed to evaluate the effects of omega-3 fish oil supplements on cognitive performance and metabolic risk measures … and to look for any links between the two (Nilsson A et al. 2012).
The authors described the context and purposes of their trial:
- “Higher [blood omega-3 fatty acid levels] have been associated with a lower risk of age related cognitive decline, and to beneficially affect cardio-metabolic risk factors. A relation exists between metabolic disorders such as type 2 diabetes and cognitive decline.”
- “Results regarding the potential effects of [dietary omega-3 fatty acids] on risk factors in healthy subjects are divergent, and studies regarding the possible relation between cardio-metabolic parameters and cognitive performance are scarce.”
- “The objective was to evaluate the effects of five weeks intake of long chain [omega-3 fatty acids] on cognitive performance in healthy individuals, and to exploit the possible relation between outcomes in cognitive tests to cardio-metabolic risk parameters.”
A research team led by Professor Inger Björck recruited 40 healthy participants aged between 51 and 72 years (Nilsson A et al. 2012).
The volunteers were divided into two groups, each of which followed one of two daily supplement regimens:
The fish oil capsules provided 1,500mg of omega-3 EPA, 1,050mg of omega-3 DHA, and 450mg of other omega-3s (mostly DPA).
Both groups took their capsules for five weeks, stopped taking pills for a five week “washout” period, and then switched groups for another five weeks of taking placebo or fish oil capsules.
After the 15-week period of the trial, their cognitive performance was then determined by tests measuring working memory (WM) and selective attention.
In addition, the researchers measured key metabolic risk factors such as blood pressure, blood triglyceride levels, fasting glucose levels, and levels of a pro-inflammatory protein called TNF-alpha.
As they reported, the results were encouraging: “Daily intake of omega-3 [fatty acids] from fish oil during five weeks significantly improved cognitive functions (working memory capacity) in healthy subjects.” (Nilsson A et al. 2012)
“In addition, inverse relations were obtained between cardio-metabolic risk factors and cognitive performance, indicating a potential of dietary prevention strategies to delay onset of metabolic disorders and associated cognitive decline.” (Nilsson A et al. 2012)
In other words, those whose metabolic risk factors improved also showed improvements in cognitive performance.
The Swedish team stressed that this link highlights the role of dietary choices in preventing or delaying cognitive and metabolic declines.
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Dullemeijer C, Durga J, Brouwer IA, van de Rest O, Kok FJ, Brummer RJ, van Boxtel MP, Verhoef P. n 3 fatty acid proportions in plasma and cognitive performance in older adults. Am J Clin Nutr. 2007 Nov;86(5):1479-85.
Narendran R, Frankle WG, Mason NS, Muldoon MF, Moghaddam B. Improved working memory but no effect on striatal vesicular monoamine transporter type 2 after omega-3 polyunsaturated Fatty Acid supplementation. PLoS One. 2012;7(10):e46832. doi: 10.1371/journal.pone.0046832. Epub 2012 Oct 3.
Nilsson A, Radeborg K, Salo I, Björck I. Effects of supplementation with n-3 polyunsaturated fatty acids on cognitive performance and cardiometabolic risk markers in healthy 51 to 72 years old subjects: a randomized controlled cross-over study. Nutr J. 2012 Nov 22;11(1):99. [Epub ahead of print]
Sydenham E, Dangour AD, Lim WS. Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database Syst Rev. 2012 Jun 13;6:CD005379. Review.
van de Rest O, Spiro A 3rd, Krall-Kaye E, Geleijnse JM, de Groot LC, Tucker KL. Intakes of (n-3) fatty acids and fatty fish are not associated with cognitive performance and 6-year cognitive change in men participating in the Veterans Affairs Normative Aging Study. J Nutr. 2009 Dec;139(12):2329-36. Epub 2009 Oct 14.