Eating junk food during childhood may lead to irreversible memory issues

Parents the world over are aware of the detrimental effects of drugs and alcohol on a child’s developing brain, but new research suggests moms and dads may need to start regarding sweets just as bad as beer. 

Research conducted at the University of Southern California found rats fed a diet full of fat and sugar during childhood and adolescence suffered long-term memory impairment continuing well into adulthood.

The study authors believe these findings show that a junk food-filled diet may disrupt a teen’s memory ability for a long time, just like in rats. According to the National Library of Medicine, mice and rats have long served as the preferred species for biomedical research animal models due to their anatomical, physiological, and genetic similarities to humans.

“Even if you put them on a healthy diet later on, the memory impairment persists well into adulthood,”  says Scott Kanoski, a professor of biological sciences at the USC Dornsife College of Letters, Arts and Sciences. 

While developing the study, Prof Kanoski and postdoctoral research fellow Anna Hayes considered prior research that uncovered a link between poor diet and Alzheimer’s disease.

Those diagnosed with Alzheimer’s disease display lower levels of a neurotransmitter called acetylcholine in their brains. The neurotransmitter aids memory and functions like learning, attention, arousal, and involuntary muscle movement.

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The researchers wondered what that might mean for younger individuals following a similar fat-filled, sugary, Western diet, especially when their brains are undergoing significant development during adolescence. By tracking the influence of the diet on the rodents’ levels of acetylcholine and having the rats undergo some memory testing, researchers successfully learned more about the critical relationship between diet and memory.

Next, the study authors tracked acetylcholine levels among a group of rats following a fatty, sugary diet and a control group of rats. They analysed their brain responses to certain tasks intended to test their memory. From there, researchers examined the rats’ brains post-mortem for any signs of disrupted acetylcholine levels.

The memory test used in the study involved allowing the rats to explore new objects in different locations. Days later, researchers reintroduced the rats to a nearly identical scene - except for the addition of one new object. Rats on the junk food diet showed signs of being unable to remember which objects they had previously seen and where. Meanwhile, those in the control group were more familiar with their surroundings.

“Acetylcholine signalling is a mechanism to help them encode and remember those events, analogous to ‘episodic memory’ in humans that allows us to remember events from our past,” Hayes explains. That signal appears not to be happening in the animals that grew up eating the fatty, sugary diet.”

Prof Kanoski emphasises that adolescence is a sensitive period for the brain, as significant brain and physiological changes occur.

“Unfortunately, some things that may be more easily reversible during adulthood are less reversible when they occur during childhood,” he says.

Luckily, the research team gave hope for intervention. Upon administering the drugs PNU-282987 and carbachol directly to the hippocampus, a brain region responsible for memory, the team successfully induced the release of acetylcholine and the rats’ memory ability returned to a good measure.

The study is published in Brain Behavior and Immunity.