The results may suggest that omega-3s protect the
brain from the loss of volume that happens with normal aging and is
seen more severely in people with dementia, the researchers say.
"The brain gets smaller during the normal aging process — about 0.5
percent per year after age 70, but dementia is associated with an
accelerated and localized process of brain shrinkage," said James Pottala, who led the study.
Pottala is an assistant professor at the University of South Dakota
Sanford School of Medicine in Sioux Falls and chief statistician for
the Health Diagnostic Laboratory in Richmond, Virginia.
He and his colleagues analyzed data from the Women's Health
Initiative Memory Study to see whether omega-3s were associated with
brain shrinkage in general, and in specific brain regions involved
in memory and other cognitive processes.
The data covered 1,111 women who were, on average, 70 years old and
had no signs of dementia at the beginning of the study. At that
time, the amounts of the omega-3 fatty acids eicosapentaenoic acid
(EPA) and docosahexaenoic acid (DHA) in their red blood cells were
DHA accounts for 30 percent to 40 percent of the fatty acids found
in brain cell membranes, and it's especially concentrated near the
synapses where the cells communicate with one another, Pottala and
his colleagues note in their report, published in the journal
Red blood cell levels of the omega-3s are good indicators of how
much a person has consumed, the researchers add.
The researchers used an omega-3 index to describe the fatty acid
levels seen among women in the study and to divide them into four
groups: women with the highest levels had an average index reading
of around 7.5 percent, while women with the lowest levels had an
average of 3.4 percent.
Eight years after the women's blood was tested, they underwent MRIs
to measure the volume of gray matter and white matter in their
The researchers found that women with the highest EPA and DHA blood
levels at the study's outset had brains that were about 2 cubic
centimeters larger overall than women with the lowest levels.
In addition, the hippocampus, a brain region critical to forming and
storing memories, was 2.7 percent larger in women who had fatty acid
levels twice as high as the average.
Of 13 specific brain regions the researchers looked at, the
hippocampus was the only one where they saw a significant
[to top of second column]
The analysis adjusted for other factors that could
influence the women's brain size, including education, age, other
health conditions, smoking and exercise.
researchers didn't measure cognitive function, only brain volume, so
they cannot say whether the size differences they saw had any link
with differences in memory or dementia risk.
The authors acknowledged other limitations in their report,
including that they did not look at whether the women's omega-3
consumption had changed over time.
It's possible that some of the participants had changed their diets
or started taking fish oil or other forms of omega-3 fatty acids,
Pottala told Reuters Health in an email.
previous study, he and his colleagues showed red blood cell EPA and
DHA levels and people's dietary fish intakes generally don't change
"If some subjects in our MRI study began taking fish oil
supplements, then the reported benefits would be underestimated,"
Pottala says higher blood levels of omega-3 fatty acids can be
achieved by dietary changes, such as eating oily fish twice a week
or taking fish oil supplements.
Since the study does not prove that blood levels of omega-3s are the
cause of the brain-size differences observed, or that those
differences have any effect on cognitive function, the researchers
caution that more research is needed to know whether raising omega-3
levels would make any difference to brain health.
Neurology, online Jan. 22, 2014.
[© 2014 Thomson Reuters. All rights
Copyright 2014 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.