Studies link omega-3s and the omega-3/6 balance to thinking, memory, and brain aging
Three new studies highlight the rare value of omega-3s to brain health.
One reinforces the brain risks of America’s extreme “omega imbalance”.
Another found novel evidence that plant-source omega-3s may aid brain health.
And the third linked higher blood levels of omega-3s to fuller blood flow in key brain regions and better scores on cognitive tests.
Before diving in, let’s recap the background that led University of Illinois researchers to perform the first study, which examined the brain effects of America’s “omega imbalance”.
The brain-health implications of America’s omega-3/6 imbalance
Historically, most humans consumed about three parts omega-6 fats to one part omega-3 fats.
But that ratio spiked sharply over the past 40 years, and most Americans now consume about 15 parts omega-6 fats to one part omega-3s.
Our genes can’t adapt that rapidly to dietary changes, and evidence from several population studies link omega-imbalanced diets — ones with too many omega-6s and too few omega-3s — to worse brain function.
Likewise, a small Canadian study published earlier this year linked the participants’ estimated omega-3 and omega-6 intakes to the danger of developing dementia … see Alzheimer’s Linked to America’s Omega-3/6 Imbalance.
In the first of our three studies, researchers added substantially stronger, blood-based evidence that Americans’ historically extreme intakes of omega-6 fats and very low omega-3 intakes can harm brain health.
Study #1 — Omega-3/omega-6 imbalance again linked to brain decline
A team from the University of Illinois Champagne-Urbana examined omega-3 and omega-6 blood levels among 94 healthy adults aged 65 to 75 years.
The goal was to look for links between the participants’ blood levels of omega-3 and omega-6 fats, the integrity of their brain structures, and related cognitive abilities known to decline early in aging (Zamroziewicz MK et al. 2018).
According to the lead author, M.D./Ph.D. student Marta Zamroziewicz, “We studied a primary network of the brain — the frontoparietal network — that plays an important role in fluid intelligence and also declines early, even in healthy aging.” (Fluid intelligence means the capacity to solve novel problems.)
She added, “In a separate study, we examined the white matter structure of the fornix, a group of nerve fibers at the center of the brain that is important for memory.” (The fornix is among the first regions damaged by Alzheimer’s disease.)
Zamroziewicz noted that the brain is a collection of interconnected parts — and that some start to deteriorate before others, along with the cognitive capacities they support.
Her team’s results showed that people with lower levels of omega-6 fatty acids and higher levels of omega-3s had a larger fornix and correspondingly better memory capacity.
“These findings have important implications for the Western diet, which tends to be misbalanced with high amounts of omega-6 fatty acids and low amounts of omega-3 fatty acids,” said Zamroziewicz.
Study #2 — Plant-source omega-3s may aid brain health
This study formed a second facet of the University of Illinois investigation led by Marta Zamroziewicz, and it involved 122 healthy adults aged 65 to 75 years (Zamroziewicz MK et al. 2017).
As she said, “Most of the research that looks at these fats focuses on the omega-3 fatty acids DHA and EPA, but those come from fish and fish oil, and most people don’t eat enough of those to really see the benefits.”
People can use a plant-source omega-3 fat called ALA — which occurs in dark, leafy greens and abounds in flaxseed, canola oil, and walnuts — to make the EPA and DHA that they need to survive and thrive.
Of those two omega-3s, DHA is far more critical to brain function, health, and performance, and the body can easily convert it into EPA as needed, while the reverse is not true.
Our bodies convert omega-3 ALA from plant foods into another omega-3 called SA, and then into EPA and DHA.
Ms. Zamroziewicz’s team linked higher blood levels of omega-3 ALA and SA with better fluid intelligence in the study participants.
And further analyses produce two other important findings:
- People with higher omega-3 ALA and SA levels tended to have larger left frontoparietal cortices.
- The size of the frontoparietal cortex predicted a participants’ performance on tests of fluid intelligence.
As Zamroziewicz said, “A lot of research tells us that people need to be eating fish and fish oil to get neuroprotective effects from [omega-3] fats, but this new finding suggests that even the [omega-3] fats that we get from nuts, seeds, and oils can also make a difference in the brain.”
We would caution that there’s little evidence that omega-3 ALA from plant foods has anything like the profound impact of dietary omega-3 DHA on brain health and performance.
Instead, the Illinois teams finding simply reinforces the obvious: Even people who eat little or no seafood can maintain good brain health if they mostly eat whole plant foods — including ones featuring ample ALA and/or antioxidants — and remain physically active.
Study #3 — Higher omega-3 levels linked to better brain blood flow and test scores
This study was led by Daniel G. Amen, M.D., who’s authored best-selling books on brain health, hosts a PBS-TV program on the subject, and operates the Amen Clinics.
We reported on his studies on reducing concussion-related brain damage in contact-sport athletes using omega-3s and exercise … see Fish Oil May Help Blunt Brain Damage and Omega-3-Based Regimen Boosted Battered NFL Brains.
His lead co-author was omega-3 researcher William S. Harris, Ph.D., of the University of South Dakota — who co-authored a related 2014 MRI study: see Omega-3s May Slow Brain Shrinkage — and they were aided by scientists from UCLA and UCSF.
Dr. Amen’s clinic specializes in “single photon emission computed tomography”, or SPECT, a type of 3-D nuclear imaging that can show blood flow in the brain, and help reveal which regions are most active.
Accordingly, SPECT images taken when people perform various cognitive tasks will show higher blood flow in specific brain regions.
In addition, the British authors of a recent evidence review concluded that SPECT scans are 65-85% accurate for diagnosing Alzheimer's disease and 72-87% accurate for diagnosing other forms of dementia (Davison CM et al. 2014).
The new study involved a random sample of 166 people from a psychiatric referral clinic who’d been tested to determine their blood levels of omega-3 EPA and DHA.
The participants were categorized into two groups:
- Lower EPA+DHA blood levels (below the 50th percentile)
- Higher EPA+DHA blood levels (above the 50th percentile)
SPECT scans were performed on 128 brain regions, and each subject also underwent computerized WebNeuro testing of their “neurocognitive” status, which encompassed their sensory-motor, memory, executive planning, attention, and emotion-perception capacities.
When the participants’ SPECT images were compared to their omega-3 levels, the results linked higher omega-3 levels to better blood flow in brain regions important for learning, memory, depression and dementia.
The results also showed statistically significant links between higher omega-3 levels and better performance on the neurocognitive (thinking, memory, and mood) tests.
Overall, the study linked higher omega-3 EPA+DHA blood levels to fuller blood flow in key regions, and to improved brain performance.
Dr. Amen summarized the meaning of their findings: “This is very important research because it shows a correlation between lower omega-3 fatty acid levels and reduced brain blood flow to regions important for learning, memory, depression and dementia.”
Evidence on the power of omega-3 fish oil supplements to reduce the symptoms of diagnosed Alzheimer's and other dementias later in life is mixed, and that's not surprising.
But these studies suggest that it's wise to load your diet with seafood and plant sources of omega-3s — and limit your intake of omega-6 fats —and to start that habit as soon as possible.
To learn more about America's omega imbalance — and the food choices that can fix it — see our Omega-3/6 Balance page, and the "Out of Balance" video you'll find there.
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