The dry, puckering sensation associated with flavanol-rich foods such as cocoa and berries may act as a direct signal to the brain, triggering changes in attention, activity, and memory through sensory pathways rather than direct systemic absorption, a new mouse study suggests.
Flavanols are poorly absorbed after ingestion, raising questions about how they influence brain function. In the new study, researchers at Shibaura Institute of Technology tested whether the astringent taste of flavanols could itself activate neural circuits linked to arousal and cognition.
In mouse experiments, the team administered single oral doses of flavanols and assessed behavior, neurotransmitter dynamics, and stress-response signaling. Compared with controls given distilled water, flavanol-treated animals showed increased spontaneous activity in open-field tests and improved performance in novel object recognition tasks – indicating enhanced exploratory behavior and short-term memory.
Neurochemical analysis revealed rapid activation of the locus coeruleus–noradrenergic system, a central regulator of attention and arousal. Using mass spectrometry imaging, the researchers detected elevated levels of noradrenaline and its precursors in multiple brain regions shortly after flavanol administration. In parallel, in situ hybridization showed increased expression of enzymes involved in noradrenaline synthesis and transport, including tyrosine hydroxylase and vesicular monoamine transporter 2.
Biochemical assays provided further evidence of stress-response activation. Urinary catecholamine levels increased following flavanol intake, particularly at higher doses, and markers of hypothalamic–pituitary–adrenal axis activity – including corticotropin-releasing hormone mRNA in the hypothalamic paraventricular nucleus – were upregulated.
“Flavanols exhibit an astringent taste. We hypothesized that this taste serves as a stimulus, transmitting signals directly to the central nervous system,” said Yasuyuki Fujii, who led the study. “As a result, it is thought that flavanol stimulation is transmitted via sensory nerves to activate the brain.”
The authors interpret this pattern of neural and hormonal responses as resembling those triggered by physical exercise. “Stress responses elicited by flavanols in this study are similar to those elicited by physical exercise,” Fujii said. “Thus, moderate intake of flavanols, despite their poor bioavailability, can improve the health and quality of life.”
Rather than acting solely through absorption, the findings suggest that sensory signaling may play a central role in how flavanol-rich foods influence brain activity.
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