Children With Fatty Diets Could Develop Mental Health Issues

16 Nov 2016 --- Children who eat excessive amounts of fatty foods may not only become obese, but could also develop cognitive and psychiatric problems when they are older. That’s according to a new study suggesting that diets rich in fat deplete the levels of a key protein known to help synapses in the brain to work properly.

Researchers say that a high fat diet leads to a dip in several forms of cognitive functions, such as behavioral flexibility and memory.

"These changes from a young age onwards are more the result of the fatty foods themselves, and the impact they have on young brains, rather than arising from the mere fact of being obese," notes Urs Meyer from ETH Zurich in Switzerland in Springer Nature's journal Molecular Psychiatry.

The researchers conducted a study in mice, and observed cognitive defects as early as four weeks after the mice were fed high-fat foods. These were evident even before the animals started gaining weight and appeared specifically in mice fed high-fat foods during adolescence, and not in mice fed the same diets during adulthood.

In order to get at the mechanisms underlying such observations, the authors focused on a frontal region in the brain known as the prefrontal cortex.

In humans, the prefrontal cortex is associated with the planning of complex actions and decision making, expressing one's personality and controlling one's social behavior.

Several human studies had shown how fat-rich diets can reduce performance on executive tasks such as problem solving and working memory, in particular in adolescents.

Researchers add that this finding is worrying in light of a marked drop in the quality of diets over the past few decades and the poor understanding of the impact these diets have on our neurons.

They also add that these effects might be particularly relevant for adolescents, as adolescence is a key period of increased caloric needs and heightened appetite for young people, and is the time when they start making more choices themselves about what to eat.

The researchers explain that adolescents eating high-fat diets may also be prone to cognitive deficits due to the immature character of the prefrontal cortex during this time frame. "This brain region is very interesting," notes French INSERM investigator Chavis, "because, unlike the rest of the brain, it is not fully developed until early adulthood."

The team believes this relative immaturity makes the prefrontal cortex very sensitive to suboptimal experiences occurring during adolescence such as trauma, excessive stress or drug abuse.

"Our study highlights that the quality of the food eaten by teenagers may also be particularly important for an optimal maturation of the prefrontal cortex," says Marie Labouesse, lead author of the study.

"We think this adolescent vulnerability to high-fat foods might be due to the hypersensitivity of a protein known as reelin," notes Labouesse.

"We saw that plasticity in the prefrontal cortex was impaired in animals fed high-fat foods during adolescence; and quite remarkably we then observed that when restoring reelin levels, both synaptic plasticity and cognitive functions went back to normal," adds Chavis.

"Our findings that high-fat diets during adolescence disrupt functioning of the adult prefrontal cortex suggest that a careful nutritional balance during this sensitive period is pivotal for reaching the full capacity of adult prefrontal functions," says Labouesse.

"Although we still need to find out the exact mechanisms by which reelin neurons get depleted during adolescence, it looks like high-fat foods could kick-start changes in how the prefrontal cortex of younger people develops."

Additionally, Reelin deficiency is also a feature repeatedly documented in brain disorders such as schizophrenia or Alzheimer's disease, something that the researchers are keen to explore further.

"Although more studies on this topic are definitely needed," warns Meyer, "high-fat diets could potentially exacerbate the reelin and synaptic deficits in patients with mental illnesses such as schizophrenia or Alzheimer's disease or even aggravate cognitive anomalies."

The researchers hope that these findings may help explain how unhealthy foods and obesity are increasingly linked to the development of neuropsychiatric and neurological conditions.