You are probably familiar with that dry and rough sensation in the mouth after eating dark chocolate or berries. Until now, you probably did not give it much importance, but a new study suggests that this sensation – known as astringency – may be much more interesting than we thought.
According to a study published earlier this year in the journal Current Research in Food Science, this sensation does not remain only in the mouth, but may serve as a direct trigger for increased brain activity. The study focused on flavanols – a group of plant compounds found, among other things, in cocoa, red wine, and berries. For many years, science has understood that flavanols are linked to improved cognitive function and reduced risk of heart disease, but until now experts have wondered how this is possible if only a small portion of them is actually absorbed into the bloodstream after eating.
This gap led researchers from the Shibaura Institute of Technology in Japan to examine an alternative explanation, suggesting that the effects of flavanols may come not only from their absorption in the body, but also from the way they activate the nervous system through the sense of taste.
Curiosity and improved learning and memory
To test the unconventional hypothesis, the researchers conducted an experiment on 10-week-old mice. The animals received doses of flavanols (25 or 50 mg per kilogram of body weight), while the control group received only water. The results showed that the mice given flavanols exhibited higher levels of activity, curiosity, and improved performance in learning and memory tasks compared to the control group.
But the truly interesting finding came from the biochemical tests. The researchers identified an increase in the activity of key neurotransmitters in the brain, including dopamine, norepinephrine, and additional substances involved in motivation, alertness, and stress response. One of the notable aspects of the study is the similarity between the effects of flavanols and physiological responses that occur during physical exercise. The researchers found that flavanol consumption activated the sympathetic nervous system – the system responsible, among other things, for the "fight or flight" response and preparing the body for stressful situations.
In addition, there was an increase in stress hormone levels (catecholamines) and activity in brain regions associated with stress regulation and response to stimuli, including the PVN nucleus in the hypothalamus. According to the researchers, this is essentially a "mild stress" that activates the body in a positive way, similar to light physical exercise.
How does taste itself affect the brain?
The explanation proposed by the researchers for this phenomenon is related to how the sensory system functions in humans and other mammals in nature. The sensation of astringency, felt as dryness or "roughness" in the mouth, is created when flavanols react with proteins in saliva. According to the hypothesis, this sensation activates sensory nerves that transmit signals directly to the central nervous system. In other words, even before the compounds are absorbed into the body, the brain already "responds" to them.
This is, for example, why many people feel they need to run to the bathroom immediately after tasting something bitter, even before the body has actually digested it. In other words, the taste itself may be an inseparable part of the health effect.
These findings align with a relatively new research approach called "Sensory Nutrition," which focuses not only on the chemical composition of food, but also on how we experience it. The researchers suggest that in the future it may be possible to develop foods that use this mechanism, meaning foods that are not only nutritious, but also trigger positive physiological responses through the senses.
A clear connection to brain health
However, despite the intriguing findings, it is important to remember that this study was conducted on mice, and therefore no direct conclusions can be drawn about humans. Nevertheless, it joins a series of studies pointing to the connection between flavanols and brain health. Previous studies, including clinical trials in humans, have already shown that flavanol consumption from cocoa can improve blood flow to the brain and support cognitive function, especially in older adults.
The novelty in the current study lies in the proposal of an additional mechanism of action, one that depends not only on digestion and absorption, but also on the sensation itself. Ultimately, it is possible that the foods we tend to avoid because of their taste, such as very dark chocolate or certain berries, are precisely the ones that activate the brain in ways we did not previously understand. And sometimes, it turns out, the unpleasant sensation in the mouth is exactly what the brain needs in order to wake up and focus.