Sugar Might Affect The Brain, UCLA Rat Study Reveals 

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The two researchers devised an experiment in which they trained a group of rats on a complicated maze twice a day for five days. After that, they split the rats into two groups. They gave both groups of rats a high-fructose corn syrup solution in place of water, but one of the groups was additionally given flaxseed oil and docosahexaenoic acid (known more commonly as DHA) -- two high-quality sources of omega-3 fatty acids, which are known to protect against neural damage.

After six weeks of the sugary diet, the researchers reintroduced the maze. They found that the sugar-only group had a much harder time recalling the maze and were slower in their problem solving. The sugar-and-omega-3 group fared better. Gomez-Pinilla theorizes that the high-sugar diet is bad for the brain for the same reason it's harmful to the body: too much fructose disrupts production of the hormone insulin, which is used by the body to regulate blood sugar. Steady blood sugar levels are essential to provide energy for things like walking and running -- but also for recalling and problem-solving.

"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 in a press release.