Large study also links high omega-6 levels linked to fuzzy thinking
Everyone would like to preserve optimal brain performance as they age.
While there are no magic bullets, a good deal of evidence links diet and exercise to healthy brain aging.
The foods linked most closely to better brain health are fatty, omega-3-rich fish and “nutrient-dense” plant foods, like fruits, vegetables, beans, nuts, and whole grains.
That said, the results of research on the ability of omega-3s to reduce age-related cognitive decline — while generally positive — have produced mixed results, with some studies finding clear benefits, while others haven’t.
Part of the reason for that mixed performance is that some studies rely on estimates of omega-3 intakes, based on participants’ notoriously unreliable answers to diet questionnaires.
In contrast, findings reported from studies that measure people’s blood levels of omega-3s and compare those to brain performance are much more reliable.
So, the positive results of a new Boston-based study that compared participants’ brain performance to their omega-3 blood levels seem especially compelling and encouraging.
Background to the new findings
Four years ago, we reported some encouraging results from the Boston Puerto Rican Health Study.
A team led by Tammy Scott, Ph.D., examined 895 participants (70 percent female), whose ages ranged from 45 to 75 years.
The volunteers were asked about their diets, to enable estimates of their intakes of omega-3 fats from plant foods, supplements, and seafood — which, as is true of most Americans, were remarkably low.
The participants took brain-function tests at the beginning of the two-year study, and again at the end.
After adjusting the results to account for lifestyle factors known to affect brain performance, the researchers linked the lowest intakes of omega-3 EPA and DHA to the greatest degree of decline in “executive function”.
Executive function is the set of mental processes that we use to plan, organize, strategize, focus attention on and remember details, and manage time and space.
Loss of executive function can also degrade "working" memory … the system that holds multiple pieces of transitory information in the mind.
Those 2014 findings fit with the results of many prior epidemiological studies but should be taken with a grain of salt, given the relative unreliability of people’s answers to diet questionnaires. (For more about the study, see Omega-3 Deficiency Predicts Faster Brain Decline.)
Now, a new group of researchers have produced a more reliable report that also involved participants in the Boston Puerto Rican Health Study — but this one was based on the participants’ actual omega-3 blood levels.
New Boston study links higher omega-3 blood levels to better brain performance
The new study comes from researchers from the University of New Hampshire, Tufts University and the University of Massachusetts Lowell (Bigornia SJ et al. 2018).
It involved 1,032 participants in the Boston Puerto Rican Health study, whose average age at the outset was 57 years, and lasted two years.
The new investigation compared participants’ omega-3 (DHA + EPA) blood levels to their performance on standard tests of brain performance — including executive function — over a two-year period.
The researchers focused on the omega-3s critical to brain and overall health — DHA and EPA — which are found only in seafood. Of the two, DHA is the most important for brain function.
The researchers measured the participants’ blood levels of omega-3 DHA + EPA, and omega-6 fatty acids.
(High blood levels of omega-6 fatty acids are common among Americans and have previously been associated with worse brain performance: see Brain Fog Linked to America’s Omega-3/6 Imbalance and its links to related articles.)
At the beginning and end of the study, the participants took standard tests designed to measure brain performance so that any changes in their scores could be compared with their omega-3 and omega-6 blood levels.
After two years, higher omega-3 blood levels were linked to better executive function.
As study co-author William Harris, Ph.D., said, “The results of this study add to the growing body of evidence correlating [higher] blood levels of omega-3s to [better] cognitive function.”
In contrast, higher blood levels of omega-6 fatty acids were linked to a 26% higher risk for developing signs of cognitive impairment over the course of the two-year study. (Higher omega-3 levels weren’t strongly linked to reduced risk of developing cognitive impairment.)
Recent Finnish study produced similar results
Two years ago, Finnish researchers published the results of a similar study.
Like the New England-based researchers, they compared participants’ omega-3 blood levels to performance on a battery of cognitive tests.
And their study produced equally positive results: “Higher ... [DHA and EPA] ... concentrations were associated with better performance on neuropsychological tests … in older men and women.”
Specifically, higher omega-3 blood levels were linked to better performance on a standard “trail-making” test that measures visual attention, task-switching, and verbal fluency.
Perhaps unsurprisingly — given its more central role in brain function — the link between higher omega-3 blood levels and better brain function was stronger for DHA than for EPA.
Importantly, the Finnish team found no significant link between higher hair levels of fish-related mercury and lesser brain performance: “Mercury exposure … had little impact on cognitive performance.” (D'Ascoli TA et al. 2016)
Why focus on omega-3s from seafood and fish oils?
Seafood-source omega-3s — DHA and EPA — are far more valuable to health, compared with the omega-3 found in dark leafy greens, walnuts, flaxseed, and some other plant foods, called ALA.
The human body can only convert 1% to 10% of dietary omega-3 ALA into omega-3 EPA and even smaller proportions of that EPA into DHA — which is by far the most important omega-3 for brain function.
In other words, seafood and fish oil are by far the best way to raise your blood and brain levels of omega-3 DHA and EPA.
Omega-3 levels in red blood cells (RBCs) that fall between 8% and 12% are strongly linked to a substantially reduced risk for cardiovascular disease, while omega-3 RBC levels of 4% or lower are strongly linked with higher risk for cardiovascular disease.
- Bigornia SJ, Scott TM, Harris WS, Tucker KL. Prospective Associations of Erythrocyte Composition and Dietary Intake of n-3 and n-6 PUFA with Measures of Cognitive Function. Nutrients. 2018 Sep 6;10(9). pii: E1253. doi: 10.3390/nu10091253.
- D'Ascoli TA, Mursu J, Voutilainen S, Kauhanen J, Tuomainen TP, Virtanen JK. Association between serum long-chain omega-3 polyunsaturated fatty acids and cognitive performance in elderly men and women: The Kuopio Ischaemic Heart Disease Risk Factor Study. Eur J Clin Nutr. 2016 Aug;70(8):970-5. doi: 10.1038/ejcn.2016.59. Epub 2016 Apr 13.
- Scott TM et al. Lower dietary intake of long-chain polyunsaturated fatty acids predict cognitive decline. Presentation Number 124.4. Experimental Biology 2014, Sunday, April 27. Accessed at http://experimentalbiology.org/
- Tucker KL, Mattei J, Noel SE, Collado BM, Mendez J, Nelson J, Griffith J, Ordovas JM, Falcon LM. The Boston Puerto Rican Health Study, a longitudinal cohort study on health disparities in Puerto Rican adults: challenges and opportunities. BMC Public Health. 2010 Mar 1;10:107. doi: 10.1186/1471-2458-10-107.