For a long time, difficulty concentrating among students and young professionals has been attributed to lack of sleep, stress or study pressure. A new study provides another clue: the quality of the diet could also influence the functioning of the brain on a daily basis. The researchers, however, urge caution: it is not a question of proving a direct cause, but of better understanding a link which could become a public health issue.

When the plate could influence the way of thinking

An oversight during an exam. Difficulty staying focused in front of a screen. The feeling of having “my head elsewhere” after several hours of work. These small moments of cognitive fatigue are part of the daily life of many young adults. But behind these often trivialized disorders, research is beginning to explore a factor that is still little considered: diet.

A study looked at the consumption of ultra-processed foods among young adults and its association with their cognitive abilities. These products, classified according to the NOVA classification, include industrial biscuits, sodas, prepared meals, salty snacks and even certain products rich in sugars, fats and additives.

“Ultra-processed foods have become a major feature of modern diets, particularly among young adults.explain authors Sara Rafiei and Mohammadreza Vafa from Iran University of Medical Sciences.

Their question is simple but important: could these foods, already associated with many chronic diseases when consumed in excess, also have an impact on the brain in the short term?

More than 400 students screened: what the cognitive tests reveal

To try to answer this, the researchers followed 416 students aged 18 to 35, with an average age of just over 22 years. All were medical students at an Iranian university. Participants’ diet was assessed using two 24-hour dietary recalls carried out several days apart. Each food consumed was then classified according to the level of processing defined by the NOVA classification.

Result: ultra-processed foods represented on average 29.5% of their daily energy intake.

The researchers then assessed their cognitive abilities using two tests:

• THE Numerical Learning Testintended to measure short-term memory;
• THE Toulouse-Piéron Testwhich assesses sustained attention and the ability to concentrate.

The results show a particularly clear association with memory. In statistical analyses, each 10% increase in the share of ultra-processed foods in daily calorie intake was associated with a 0.54 point decrease in memory score. Students in the group consuming the most ultra-processed foods had an average memory score of 17.59, compared to 19.60 among those who consumed the least.

For concentration, the link also existed, but it was much weaker: each 10% increase in ultra-processed foods was associated with a drop of 0.138 points on the attention test. After statistical adjustment, however, the differences between groups were no longer significant. “What surprised us the most was the consistency of the association with memory.”said the authors.

A young brain, but perhaps already exposed

These results take on a particular dimension because they concern a period of life when cognitive abilities are generally considered optimal. Until now, research on ultra-processed foods and cognitive decline has mostly focused on older adults, with associations observed with the risk of dementia or Alzheimer’s disease. This new study explores another question: is it possible that certain effects appear much earlier?

Researchers observe in particular that memory performance remains relatively stable when ultra-processed foods represent less than 20% of daily energy intake, then seems to decrease further beyond that. However, they specify that this is not an established medical threshold, but only a statistical trend observed in their data.

Several biological mechanisms could explain this association.

• A diet very rich in ultra-processed products may be less favorable for intake of micronutrients essential to brain function;
• It can also promote an excess of sugars and saturated fats, inflammatory phenomena, insulin resistance or even a disruption of the intestinal microbiota, whose interactions with the brain – via what scientists call the gut-brain axis – are today the subject of much research.

“Our study suggests that associations between ultra-processed food consumption and cognitive performance may already be detectable as early as early adulthood.”summarize the researchers.

An alert, not a condemnation: what science still needs to demonstrate

Faced with these results, the authors caution against drawing any definitive conclusions. The study has a major limitation: it is cross-sectional. In other words, researchers observed an association at some point, but they cannot demonstrate that ultra-processed foods directly cause a decline in memory or concentration.

Other limitations exist: the participants self-reported their diet, which can lead to memorization errors, and all were medical students at the same university. Their profile therefore does not necessarily represent all young adults.

Despite these precautions, the researchers’ message is clear: diet could play a much more immediate role than previously imagined in brain health.

“The key message is that diet can matter not only to your future health, but also to how your brain works today.”they emphasize.

The next step will be to follow populations over several years and test whether reducing the importance of ultra-processed foods in favor of less processed foods can really improve memory and cognitive abilities. Because behind the numbers, the issue is profoundly human: understanding how our daily choices can preserve, from a very young age, what is most precious to us — our ability to learn, think and remember.