"Should Vegans Take DHA to Preserve Brain Function?"
We are all fatheads.
About a half of the dry weight of our brain is fat.
Lower levels of the long-chain omega 3 fat, DHA,
in some areas of Alzheimer's brains
got people thinking that maybe DHA was protective.
Since the level of DHA in the brain tends to correlate
with the level of DHA in the blood,
one can do cross-sectional studies of dementia and pre-dementia patients,
and they do tend to have lower levels of both long-chain omega 3's, EPA and DHA,
circulating in their bloodstream.
Now this doesn't necessarily mean that lower omega 3 levels
cause cognitive impairment.
It was just a snapshot in time, so you don't know which came first.
Maybe the dementia led to a dietary deficiency,
rather than a dietary deficiency leading to dementia.
What you want is to measure long-chain omega-3 levels at the beginning
and then follow people over time,
and indeed there may be a slower rate of cognitive decline
in those that start out with higher levels.
And you can actually see the difference on MRI.
Thousands of older men and women had their levels checked
and were scanned and then re-scanned,
and the brains of those with higher levels looked noticeably healthier 5 years later.
The size of our brain actually shrinks as we get older, starting around age 20.
Between ages 16 and 80 our brain loses about 1% of its volume
every two to three years, such that by the time
we're in our 70's, our brain has lost
26% of its size, and ends up smaller than that of 2 to 3 year old children.
As we age, our ability to make the long chain omega 3s like DHA
from the short chain omega 3s in plant foods such as flaxseeds,
chia seeds, walnuts, and greens may decline.
And so researchers compared DHA levels to brain volumes
in the Framingham study and lower DHA levels were associated
with smaller brain volumes, but this was just from a snapshot in time,
until this study was published.
Higher EPA and DHA levels correlated with larger brain volume eight years later.
While normal aging results in overall brain shrinkage,
having lower long-chain omega-3's may signal increased risk.
The only thing one would need now to prove cause and effect
is a randomized controlled trial showing we can actually slow brain loss
by giving people extra long-chain omega 3's,
but the trials to date showed no cognitive benefits from supplementation until now.
Double-blind randomized interventional study providing evidence
for the first-time that extra long chain omega 3's exert positive effects
on brain functions in healthy older adults,
a significant improvement in executive function after six and a half months
of supplementation, and significantly less brain shrinkage compared to placebo.
This kind of gray matter shrinkage in the placebo
might be considered just normal brain aging,
but it was significantly slowed in the supplementation group.
They also described changes in the white matter of the brain,
increased fractional anisotropy, and decreases in mean and radial diffusivity—
terms I've never heard of, but evidently they imply greater structural integrity.
So having sufficient long-chain omega 3's, EPA and DHA,
may be important for preserving brain function and structure.
The next question becomes what's sufficient, and how do you get there?
The Framingham study found what appears to be a threshold value
around an omega 3 index of 4.4, which is a measure of our EPA and DHA levels.
Having more or much more than 4.4 didn't seem to matter,
but having less was associated with accelerated brain loss,
equivalent to like an extra two years of brain aging.
That comes out to be about a teaspoon less brain matter,
so it's probably good to have an omega 3 index over 4.4.
The problem is that people who don't eat fish may be under 4.4.
Nearly two-thirds of vegans may fall below 4,
suggesting a substantial number of vegans
have an omega-3 status associated with accelerated brain aging.
The average American just exceeds the threshold at about 4.5, though if your age
and gender match for the vegans, ironically the omnivores did just as bad—
there's not a lot of long-chains in Big Macs either.
But having a nutrient status no worse
than those eating a standard American diet is not saying much.
All we need now is a study that gives those with such low levels
some pollutant-free EPA and DHA and see how much it takes
to push people past the threshold, and here we go.
They took those eating vegan with levels under 4,
gave them algae-derived EPA and DHA,
and about 250 mg a day took them from an average of 3.1
over the line to 4.8 within four months.
And so that's why I recommend everyone eat a plant-based diet
along with contaminant-free EPA and DHA
to get the best of both worlds: omega 3 levels associated
with brain preservation while minimizing exposure to toxic pollutants.