While some research suggests that a diet high in
omega-3 fatty acids can protect brain health, a
large clinical trial by researchers at the National
Institutes of Health found that omega-3 supplements
did not slow cognitive decline in older persons.
With 4,000 patients followed over a five-year
period, the study is one of the largest and longest
of its kind. It was published yesterday in the
Journal of the American Medical Association.
NIH study raises doubt about any benefits omega-3 and dietary supplements like these may have for cognitive decline. (Photo curtesy of NEI).
“Contrary to popular belief, we didn’t see any
benefit of omega-3 supplements for stopping
cognitive decline,” said Emily Chew, M.D., deputy
director of the Division of Epidemiology and
Clinical Applications and deputy clinical director
at the National Eye Institute (NEI), part of NIH.
Dr. Chew leads the Age-Related Eye Disease Study (AREDS),
which was designed to investigate a combination of
nutritional supplements for slowing age-related
macular degeneration (AMD), a major cause of vision
loss among older Americans.
That study established that daily high doses of
certain antioxidants and minerals — called the AREDS
formulation — can help slow the progression to
advanced AMD.
A later study, called AREDS2, tested the addition of
omega-3 fatty acids to the AREDS formula. But the
omega-3’s made no difference. Omega-3 fatty acids
are made by marine algae and are concentrated in
fish oils; they are believed to be responsible for
the health benefits associated with regularly eating
fish, such as salmon, tuna, and halibut.*
Where studies have surveyed people on their dietary
habits and health, they’ve found that regular
consumption of fish is associated with lower rates
of AMD, cardiovascular disease, and possibly
dementia. “We’ve seen data that eating foods with
omega-3 may have a benefit for eye, brain, and heart
health,” Dr. Chew explained.
Omega-3 supplements are available over the counter
and often labeled as supporting brain health. A
large 2011 study found that omega-3 supplements did
not improve the brain health of older patients with
preexisting heart disease.
With AREDS2, Dr. Chew and her team saw another
opportunity to investigate the possible cognitive
benefits of omega-3 supplements, she said. All
participants had early or intermediate AMD. They
were 72 years old on average and 58 percent were
female. They were randomly assigned to one of the
following groups:
. Placebo (an inert
pill)
. Omega-3 [specifically docosahexaenoic acid (DHA,
350 mg) and eicosapentaenoic acid (650 mg)]
. Lutein and zeaxanthin (nutrients found in large
amounts in green leafy vegetables)
. Omega-3 and Lutein/zeaxanthin
Because all participants were at risk for worsening
of their AMD, they were also offered the original or
a modified version of the AREDS formulation (without
omega-3 or lutein/zeaxanthin).
Participants were given cognitive function tests at
the beginning of the study to establish a baseline,
then at two and four years later. The tests, all
validated and used in previous cognitive function
studies, included eight parts designed to test
immediate and delayed recall, attention and memory,
and processing speed. The cognition scores of each
subgroup decreased to a similar extent over time,
indicating that no combination of nutritional
supplements made a difference.
Alzheimer’s disease, which is the most common cause
of dementia and affects as many as 5.1 million
Americans age 65 and older in the U.S., may triple
in the next 40 years. Some research has examined the
potential benefits of DHA for Alzheimer’s. Studies
in mice specially bred to have features of the
disease found that DHA reduces beta-amyloid plaques,
abnormal protein deposits in the brain that are a
hallmark of Alzheimer’s, although a clinical trial
of DHA showed no impact on people with mild to
moderate Alzheimer’s disease.
“The AREDS2 data add to our efforts to understand
the relationship between dietary components and
Alzheimer’s disease and cognitive decline,” said
Lenore Launer, Ph.D. senior investigator in the
Laboratory of Epidemiology and Population Science at
the National Institute on Aging.
“It may be, for example, that the timing of
nutrients, or consuming them in a certain dietary
pattern, has an impact. More research would be
needed to see if dietary patterns or taking the
supplements earlier in the development of diseases
like Alzheimer’s would make a difference.”
* Other omega-3 fatty acids are found in plant foods
such as flaxseed, walnuts, soy products, and canola
and soybean oils. Specific omega-3 fatty acids from
these sources were not studied.
For more information about AMD and AREDS2, visit
https://nei.nih.gov/areds2.
For more information
Age-Related Eye Disease Study 2 (AREDS2) Research
Group. “Effect of Omega-3 Fatty Acids, Lutein/Zeaxanthin,
or other Nutrient Supplementation on Cognitive
Function: The AREDS2 Randomized Clinical Trial.”
JAMA,
published online August 25, 2015.
National Eye Institute (NEI)
MDN |