This is your brain on sugar: UCLA study shows high-fructose diet sabotages learning, memory

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Eating more omega-3 fatty acids can offset damage, researchers say
By Elaine Schmidt May 15, 2012

A new UCLA rat study is the first to show how a diet steadily high in
fructose slows the brain, hampering memory and learning — and how
omega-3 fatty acids can counteract the disruption. The peer-reviewed
Journal of Physiology publishes the findings in its May 15 edition.

"Our findings illustrate that what you eat affects how you think," said
Fernando Gomez-Pinilla, a professor of neurosurgery at the David Geffen
School of Medicine at UCLA and a professor of integrative biology and
physiology in the UCLA College of Letters and Science. "Eating a
high-fructose diet over the long term alters your brain's ability to
learn and remember information. But adding omega-3 fatty acids to your
meals can help minimize the damage."

While earlier research has revealed how fructose harms the body through
its role in diabetes, obesity and fatty liver, this study is the first
to uncover how the sweetener influences the brain.

Sources of fructose in the Western diet include cane sugar (sucrose) and
high-fructose corn syrup, an inexpensive liquid sweetener. The syrup is
widely added to processed foods, including soft drinks, condiments,
applesauce and baby food. The average American consumes roughly 47
pounds of cane sugar and 35 pounds of high-fructose corn syrup per year,
according to the U.S. Department of Agriculture.

"We're less concerned about naturally occurring fructose in fruits,
which also contain important antioxidants," explained Gomez-Pinilla, who
is also a member of UCLA's Brain Research Institute and Brain Injury
Research Center. "We're more concerned about the fructose in
high-fructose corn syrup, which is added to manufactured food products
as a sweetener and preservative."

Gomez-Pinilla and study co-author Rahul Agrawal, a UCLA visiting
postdoctoral fellow from India, studied two groups of rats that each
consumed a fructose solution as drinking water for six weeks. The second
group also received omega-3 fatty acids in the form of flaxseed oil and
docosahexaenoic acid (DHA), which protects against damage to the
synapses — the chemical connections between brain cells that enable
memory and learning.

"DHA is essential for synaptic function — brain cells' ability to
transmit signals to one another," Gomez-Pinilla said. "This is the
mechanism that makes learning and memory possible. Our bodies can't
produce enough DHA, so it must be supplemented through our diet."

The animals were fed standard rat chow and trained on a maze twice daily
for five days before starting the experimental diet. The UCLA team
tested how well the rats were able to navigate the maze, which contained
numerous holes but only one exit. The scientists placed visual landmarks
in the maze to help the rats learn and remember the way.

Six weeks later, the researchers tested the rats' ability to recall the
route and escape the maze. What they saw surprised them.

"The second group of rats navigated the maze much faster than the rats
that did not receive omega-3 fatty acids," Gomez-Pinilla said. "The
DHA-deprived animals were slower, and their brains showed a decline in
synaptic activity. Their brain cells had trouble signaling each other,
disrupting the rats' ability to think clearly and recall the route
they'd learned six weeks earlier."

The DHA-deprived rats also developed signs of resistance to insulin, a
hormone that controls blood sugar and regulates synaptic function in the
brain. A closer look at the rats' brain tissue suggested that insulin
had lost much of its power to influence the brain cells.

"Because insulin can penetrate the blood–brain barrier, the hormone may
signal neurons to trigger reactions that disrupt learning and cause
memory loss," Gomez-Pinilla said.

He suspects that fructose is the culprit behind the DHA-deficient rats'
brain dysfunction. Eating too much fructose could block insulin's
ability to regulate how cells use and store sugar for the energy
required for processing thoughts and emotions.

"Insulin is important in the body for controlling blood sugar, but it
may play a different role in the brain, where insulin appears to disturb
memory and learning," he said. "Our study shows that a high-fructose
diet harms the brain as well as the body. This is something new."

Gomez-Pinilla, a native of Chile and an exercise enthusiast who
practices what he preaches, advises people to keep fructose intake to a
minimum and swap sugary desserts for fresh berries and Greek yogurt,
which he keeps within arm's reach in a small refrigerator in his office.
An occasional bar of dark chocolate that hasn't been processed with a
lot of extra sweetener is fine too, he said.

Still planning to throw caution to the wind and indulge in a hot-fudge
sundae? Then also eat foods rich in omega-3 fatty acids, like salmon,
walnuts and flaxseeds, or take a daily DHA capsule. Gomez-Pinilla
recommends one gram of DHA per day.

"Our findings suggest that consuming DHA regularly protects the brain
against fructose's harmful effects," said Gomez-Pinilla. "It's like
saving money in the bank. You want to build a reserve for your brain to
tap when it requires extra fuel to fight off future diseases."

The UCLA study was funded by the National Institute of Neurological
Disorders and Stroke. Gomez-Pinilla's lab will next examine the role of
diet in recovery from brain trauma.

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