Junk food is the English term for all unhealthy food, such as sweets, chocolates, soft drinks or hamburgers. This type of food is not recommended for anyone, especially children and young people, who are its main consumers.
Recently, a study carried out by the University of Southern California (USC) concluded that consuming this type of diet during the crucial years of brain development damages long-term memory.
Caused by a reduction in a neurotransmitter associated with Alzheimer's disease, the memory impairment was not reversed by switching to a healthy diet in early adulthood.
The scientists analyzed how a diet high in fat and sugar damages an adolescent's brain, conducting their research on young and adolescent rats.
"What we were able to conclude not only in this article, but in some of our other recent work, is that rats that grew up on a junk food diet have memory problems that don't go away," summarized Scott Kanoski, professor of Biological Sciences at USC. "If we change their diet to a healthy one, the effects remain into adulthood."
In the experiments, the guinea pigs were fed a junk food diet from the 26th postnatal day until the 56th postnatal day, representing the juvenile and adolescent development periods.
Afterwards, the rats on this diet were changed to a healthier one, a change that was accompanied by various tests, in particular to see if the hippocampus-dependent episodic memory had been compromised.
This is the long-term memory of everyday events that occurred at specific times and places, such as memories of a 7th birthday party, for example.
The test consisted of letting the rats explore new objects in different locations. Days later, they were reintroduced to an almost identical scene, which contained a new object.
The scientists found that this diet impaired episodic memory, a damage that continued even after they changed the diet to a healthier one.
Compared to the rats on the control diet, which showed familiarity with the scene, the rats on the junk food diet showed signs that they could not remember the object they had seen before or where they had seen it.
As the hippocampus depends on acetylcholine for proper memory function, and levels of this neurotransmitter also tend to be particularly low in the brains of people with Alzheimer's disease, the scientists were particularly interested in analyzing how this diet would affect their levels.
They concluded that the animals that grew up eating this fatty, sugary diet showed no evidence of acetylcholine signaling, a mechanism that helps them encode and remember certain events.
There were also changes in the gut microbiome, but these were corrected when the healthy diet was introduced. The fact that the health of the microbiome was restored, but memory impairment persisted, suggests that acetylcholine was the cause of these deficiencies.
The researchers were only able to reverse the memory deficits with the use of drugs that mimic acetylcholine.
The scientific article with the latest findings was published this month in Brain, Behavior, and Immunity.
