Fish-rich diets and their omega-3 fatty acids reduce the risk of stroke, cardiovascular disease, and sudden cardiac death.
These well-documented benefits explain why the American Heart Association and public health agencies praise fish and omega-3 fish oil.
Meanwhile some, though not all, epidemiological (diet-health survey) studies link diets rich in fatty fish to a lower risk for depression and Alzheimer's or other forms of dementia (see the Omega-3s & Brain Health section of our news archive).
Last year, we reported on three studies suggesting that omega-3s boost brain volume and function ... and the growth of brain cells and brain-cell networks.
Now, a study from UCLA shows that older adults with higher blood levels of omega-3s from fish or fish oil performed better on tests of mental functioning – and suffered less age-related brain shrinkage – than participants with lower omega-3 levels (Tan ZS et al. 2012).
“People with lower blood levels of omega-3 fatty acids had lower brain volumes that were equivalent to about two [extra] years of structural brain aging,” said lead author Zaldy S. Tan, M.D., MPH. (AAN 2012)
Blood tests raise study's reliability
For the new study, researchers from the University of California, Los Angeles (UCLA) School of Medicine recruited 1,575 men and women – average age 67 – who were free of dementia.
The volunteers were participating in the Framingham Offspring Study, and were predominately white.
They all underwent MRI brain scans and were given tests measuring mental function, body mass index, and the levels of omega-3 fatty acids in their red blood cells.
The UCLA team found that the participants whose red blood cell levels of omega-3 DHA fell in the bottom fourth (quartile) had smaller brain volumes than those with higher DHA blood levels.
(Of the two major omega-3s found in virtually all human cells – DHA and EPA – only omega-3 DHA is essential to brain-cell structure/function … and consequently necessary to memory, thinking, and mood regulation.)
In addition, the participants whose blood levels of both key omega-3s (EPA+DHA) fell in the bottom fourth scored lower on mental tests covering visual memory and “executive” functions, problem-solving, multi-tasking, and abstract thinking.
Both the brain volume and brain function findings took into account the known effects of age, sex, and other factors on brain volume and mental acuity, in order to isolate the effects of higher or lower omega-3 levels.
Previous research compared the risk of dementia to the amount of omega-3 fatty acids in people's blood plasma, which reflects how much people had eaten in the past few days.
In contrast, by measuring omega-3 levels in the subjects' red blood cell membranes, the UCLA researchers could more accurately estimate the amount of omega-3s that participants had consumed in the past several months.
As Dr. Tan said, “This represents their average intake of fatty acids, not just a snapshot.” (Storrs C 2012)
Authors explain results, praise fatty fish
The UCLA results link lower red blood cell (RBC) levels of DHA and EPA in late middle age to smaller brain volumes and a “vascular” pattern associated with cognitive (thinking, decision-making) impairments in persons who do not yet display clinical signs of dementia.
Dr. Tan has been with the Framingham Heart Study for the past 10 years, where his research focuses on the epidemiology of Alzheimer's disease and related dementias.
He proposed one explanation for their findings: “We feel [that omega-3] fatty-acid consumption exerts a beneficial effect on brain aging by promoting vascular health. This might include reducing blood pressure and inflammation.” (Storrs C 2012)
And Dr. Tan made a key point: “… people who are already consuming fish as part of a balanced diet can take stock in the promising findings of this study that omega-3 fatty acid may benefit not only their heart but their brain as well.” (Brooks M 2012)
American Academy of Neurology (AAN). Low Levels of Omega-3 Fatty Acids May Cause Memory Problems. February 21, 2012. Accessed at http://www.newswise.com/articles/low-levels-of-omega-3-fatty-acids-may-cause-memory-problems
Brooks M. More Evidence Omega-3 Rich Diet May Protect Aging Brain. Medscape.com. February 27, 2012. Accessed at http://www.medscape.com/viewarticle/759296
Storrs C. Omega-3 Fatty Acids May Protect the Aging Brain. Health.com. February 27, 2012. Accessed at http://news.health.com/2012/02/27/omega-3-fatty-acids-may-protect-the-aging-brain/
Tan ZS, Harris WS, Beiser AS, Au R, Himali JJ, Debette S, Pikula A, Decarli C, Wolf PA, Vasan RS, Robins SJ, Seshadri S.Red blood cell omega-3 fatty acid levels and markers of accelerated brain aging. Neurology. 2012 Feb 28;78(9):658-64. Accessed at http://www.neurology.org/content/78/9/658.abstract
Wheeler M. Brain food: Study provides further confirmation that eating fish is good for you; Structural brain aging associated with lack of omega-3 acids in diet. UCLA. February 27, 2012. Accessed at http://newsroom.ucla.edu/portal/ucla/further-confirmation-that-eating-229522.aspx