Diet rich in sugar and fat in adolescence harms memory, study says

A new study led by USC researchers (University of Southern California) showed that a diet rich in “junk food ” — an English term to refer to foods rich in calories and of low nutritional quality such as ultra-processed foods and foods with a high sugar content — during adolescence can damage memory over time.

In the study, researchers fed adolescent mice a high-fat, high-sugar diet and found that the memory capacity of these models was impaired in the long term . The discovery was published in the May issue of the magazine Brain, Behavior, and Immunity.

“What we see not just in this paper, but in some of our other recent work, is that if these mice grew up on this diet of junk foodso they have memory problems that don't go away,” says Scott Kanoski, professor of biological sciences in the USC Dornsife College of Letters, Arts and Sciences in statement. “If you simply put them on a healthy diet, these effects unfortunately last into adulthood.”

Relationship between power and memory

To carry out the study, the researchers took into account that previous research had already shown a relationship between poor diet and Alzheimer's disease which leads to progressive loss of memory and cognitive abilities.

People with Alzheimer's tend to have lower levels of a neurotransmitter called acetylcholine in the brain. It is essential for memory and functions such as learning, attention and involuntary muscle movements.

Given this, the team of researchers wondered whether this could cause long-term harm to young people who are following a diet high in fat and sugar, especially during adolescence, a phase in which the brain is still undergoing significant development.

Therefore, the researchers decided to track acetylcholine levels in a group of rats that were receiving a fatty, sugary diet and in a second control group of rats — which were not receiving the same food.

The team analyzed brain responses to certain tasks designed to test the rodents' memory. The tests included exploring objects in a given scenario. Days later, the rats were reintroduced to the same scene, but with the addition of a new object.

According to the study, mice that followed a diet with “junk food” showed signs that they could not remember which object they had previously seen and in which place. The rats in the control group showed familiarity with the task.

The rats' brains were also examined after their deaths, looking for signs of changes in acetylcholine levels.

“Acetylcholine signaling is a mechanism to help them encode and remember these events, analogous to 'episodic memory' in humans, which allows us to remember events from our past,” explained study lead author Anna Hayes. “This signal does not appear to be happening in animals that grew up eating a fatty, sugary diet.”

Damages may be less reversible when they occur in adolescence

According to the researchers, adolescence is a very sensitive period for the brain , as important developmental changes occur there. “Unfortunately, some things that may be more easily reversible during adulthood are less reversible when they occur during childhood,” says Kanoski.

However, there is still hope for intervention. The researcher says that, in another study, the team examined whether memory damage in rats that were raised on a diet with junk food could be reversed with the use of medications that induce the release of acetylcholine.

For this, two medications were used, PNU-282987 and carbachol. When administered directly to the hippocampus, the region of the brain that controls memory, the ability to remember was restored. However, without this medical intervention, researchers believe that further studies are needed to find out how to reverse memory problems caused by poor diet.