Junk Food Diet Leaves Lasting Damage in Adolescent Brains 

by Denis Storey
May 7, 2024 at 11:55 AM UTC

A new study reveals that rats fed a junk food diet showed impaired memory, potentially linked to decreased acetylcholine levels.

Clinical relevance: A new study reveals that rats fed a junk food diet showed impaired memory, potentially linked to decreased acetylcholine levels.

  • Researchers observed lower acetylcholine levels in the rats fed the unhealthy diet.
  • The results suggest that unhealthy diets – especially during adolescence – could have long-term effects on brain function.
  • Intervention with specific drugs restored memory functions.

It appears the damage from junk food extends far beyond the waistline. A new paper – appearing in the latest issue of Brain, Behavior, and Immunity – reports that rats fed a fatty, high-sugar diet struggled with impaired memory.

“What we see not just in this paper, but in some of our other recent work, is that if these rats grew up on this junk food diet, then they have these memory impairments that don’t go away,” Scott Kanoski, one of the paper’s authors, explained. “If you just simply put them on a healthy diet, these effects unfortunately last well into adulthood.”

Junk Food and Acetylcholine

Anna Hayes, lead author and postdoctoral research fellow at the University of Southern California stumbled across a study a couple of years ago that suggested a link between an unhealthy diet and Alzheimer’s disease. The paper claimed that Alzheimer’s patients suffered from lower levels of the neurotransmitter, which plays a crucial in memory and related tasks, such as learning, attention, arousal, and involuntary muscle movement.

Hayes wondered if the suspect identified in that paper – acetylcholine – might be responsible for any other memory-related issues. So her team sought to find out what happened to children on similar diets, given how crucial adolescence is to brain development.

To that end, the researchers followed the Western diet’s impact on a mischief of rats. The team tracked the subjects’ acetylcholine levels while running the rats through some memory tests, and then analyzed the rats’ brains post-mortem for signs of disrupted acetylcholine levels.

The researchers gauged the rats’ memories by letting them explore new objects in different locations. Days later, the researchers returned the rats to the same setting, but with the addition of a single new object.

Rats on the junk food diet showed signs they couldn’t remember which object they had seen before. Those in the control group showed no such problems.

“Acetylcholine signaling 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 said. “That signal appears to not be happening in the animals that grew up eating the fatty, sugary diet.”

The Importance of Adolescence – and Intervention

Kanoski, a professor of biological sciences at the USC Dornsife College of Letters, Arts, and Sciences, reiterated how sensitive adolescence is to the human brain – and how the damage incurred at that time can linger for years.

“I don’t know how to say this without sounding like Cassandra and doom and gloom,” he said, “but unfortunately, some things that may be more easily reversible during adulthood are less reversible when they [occur] during childhood.”

Kanoski added, though, that there is hope for intervention. Kanoski elaborated that in a subsequent round of tests, the researchers looked at whether the memory damage in the rats raised on the junk food diet could be reversed with treatment. So the team administered two drugs, PNU-282987 and carbachol, and found that those treatments, delivered straight to the hippocampus, restored the rats’ memories.

“Overall, this work identifies a link between early life diet and impaired ACh neurotransmission in the HPC. Whether these findings have translational relevance to the etiology of human dementia warrants further investigation,” the researchers concluded.

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