Sugar Can Make You Stupid

A new study out of the University of California-Los Angeles shows that a high-fructose diet sabotages learning and memory in rats. The study, published in the Journal of Physiology, also shows how omega-3 fatty acids can counteract that sabotage.

“Our findings illustrate that what you eat affects how you think,” said Dr. 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 revealed how fructose harms the body through its role in diabetes, obesity and fatty liver, this study uncovers how the sweetener influences the brain, according to the researchers.

The UCLA team concentrated on high-fructose corn syrup, an inexpensive liquid six times sweeter than cane sugar that is commonly added to processed foods from soft drinks to baby food. The average American consumes more than 40 pounds of high-fructose corn syrup each year, according to the U.S. Department of Agriculture.

“We’re not talking about naturally occurring fructose in fruits, which also contain important antioxidants,” said Gomez-Pinilla. “We’re concerned about high-fructose corn syrup that is added to manufactured food products as a sweetener and preservative.”

Gomez-Pinilla and study co-author Rahul Agrawal, Ph.D., 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,” he 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 research 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.

“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.”

Those 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. “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. Our study shows that a high-fructose diet harms the brain as well as the body. This is something new.”

Gomez-Pinilla advises people to keep fructose intake to a minimum and swap sugary treats for fresh berries and Greek yogurt. An occasional bar of dark chocolate that hasn’t been processed with a lot of extra sweetener is fine too, he said.

Still have a sweet tooth? Go ahead and indulge, but also eat foods rich in omega-3 fatty acids, like salmon, walnuts and flaxseeds, or take a daily DHA capsule, he said, recommending 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.”