A soda as a snack, a soft drink in front of the screens, a sports drink after training: for many teenagers, it has become automatic. Parents think first of sugar and excess weight, rarely of the brain. However, a new American study looked at what these drinks do to the memory and concentration of high school students, with an angle that is still little known in France.
Soda, sleep and cognitive difficulties
According to this work published in the journal Nutritional Neuroscienceled by Shuo Feng of the Department of Health Behavior at Texas A and M University, the adolescent brain in full reorganization would be particularly sensitive to
daily soda consumption and sports drinks. Researchers explored a key link between these sugary drinks and cognitive difficulties: sleep.
For this analysis, Shuo Feng relied on 2021 data from the Youth Risk Behavior Surveillance Survey, a large national survey conducted by the Centers for Disease Control and Prevention (CDC) among 8,229 American high school students. Adolescents reported how often they drank soda and sports drinks, how many hours they slept on average, and whether they had “severe difficulty concentrating, remembering, or making decisions“.
Comparing non-drinkers, occasional drinkers, and daily drinkers, the study shows that teens who drink soda every day are about one and a half times more likely to report cognitive difficulties. Daily sports drinks are especially associated with these difficulties among girls (+39%), the effect being less clear among boys.
Sugar and caffeine affect teens’ sleep and brains
Analyzes also show that high consumption of sugary drinks goes hand in hand with fewer hours of sleep, and that this reduction in sleep duration explains part of the link with cognitive disorders. The caffeine found in many sodas works by blocking adenosine, a molecule that signals the brain that it’s time to sleep. Sugar, for its part, stimulates the dopaminergic reward system, located mainly in the hypothalamus, which regulates sleep and memory. Excessive and continuous stimulation of the reward system during adolescence can alter gene expression in the hypothalamus. This part of the brain is responsible for regulating several bodily functions, including sleep cycles and memory. Over time, these chemical changes can increase the risk of developing cognitive disorders.
During adolescence, synaptic plasticity is maximal and the
prefrontal cortexinvolved in impulse planning and control, is still under construction. Estrogens, particularly estradiol, influence this plasticity and cerebral blood flow, which could explain certain differences between girls and boys.
A bottle of sports drink of around 600 ml contains around 34 g of sugar, whereas an equivalent volume of soda provides almost double, while sometimes being highly caffeinated. This difference in sugar could lead to less stimulation of the dopamine reward system in those who consume sports drinks. In addition, these drinks are often ingested during physical activities. Indeed, physical activity is known to promote metabolism and hormonal regulation. This could allow the body to eliminate harmful substances more effectively, and thus reduce certain harmful effects on the brain. However, the study indicates that in girls who consume these drinks daily, the negative cognitive effects persist.
What these results change for teenagers and those around them
The authors point out that this data remains a snapshot at a given moment: it is impossible to say if sodas cause the problems, or if teenagers in difficulty turn more towards sugary drinks. Soda consumption and assessment of cognitive difficulties rely on adolescents’ responses, which can lead to errors. Future research should aim to confirm these findings using objective measurement methods. Wearable devices could offer more detailed information on sleep quantity and quality.
Other work in Australia has shown that excessive junk food consumption is linked to poor sleep quality in adolescents. The authors of the American study conclude with a message of common sense: “Reducing the consumption of sugary drinks and promoting healthier behaviors could improve sleep and cognitive health in young people..