Study of the Day: A Diet Loaded With Sugar Makes Rats Dumber

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New research in the Journal of Physiology suggests that fructose disrupts learning and memory, but omega-3 fatty acids can help.

Study of the Day
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PROBLEM: The average American consumes roughly 47 pounds of cane sugar and 35 pounds of high-fructose corn syrup per year, mostly through processed foods like soft drinks, condiments, and desserts. Though previous studies have shown how these sweeteners harm the body through its role in diabetes, obesity, and fatty liver, it was unclear if they had impact on mental processes.

METHODOLOGY: University of California, Los Angeles, researchers Rahul Agrawal and Fernando Gomez-Pinilla trained two groups of rats on a maze twice daily for five days before serving them a fructose solution as drinking water for six weeks. The second group also received omega-3 fatty acids, which protect against damage to the synapses or the chemical connections between brain cells that enable memory and learning. After this experimental diet period, the researchers tested the rats' ability to recall the visual landmarks the scientists installed to help them escape the maze.

RESULTS: The second group of rats remembered the correct route and were able to exit much faster than the rats that did not receive omega-3 fatty acids in the form of docosahexaenoic acid (DHA) and flaxseed oil. A closer look at the brains of the DHA-deprived mammals showed a decline in synaptic activity and signs of resistance to insulin, a hormone that controls blood sugar and regulates synaptic function.

CONCLUSION: A high-fructose diet sabotages learning and memory, but omega-3 fatty acids can partially offset the damage.

IMPLICATION: Gomez-Pinilla says consuming one gram of DHA per day through foods rich in omega-3 fatty acids like salmon, walnuts, and flaxseeds can protect the brain against fructose's dumbing effects. "It's like saving money in the bank," he says in a statement. "You want to build a reserve for your brain to tap when it requires extra fuel to fight off future diseases."

SOURCE: The full study, "Metabolic Syndrome' in the Brain: Deficiency in Omega-3 Fatty Acid Exacerbates Dysfunctions in Insulin Receptor Signalling and Cognition," is published in the Journal of Physiology.

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Hans Villarica writes for and produces The Atlantic's Health channel. His work has appeared in TIME, People Asia, and Fast Company.

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