Chewing as a Brainstem-Mediated Stress Modulator: An Evolutionary Hypothesis Linking Orofacial Neural Activation to Emotional Eating and Obesity

This manuscript proposes a novel neurophysiological and evolutionary hypothesis that chewing functions as an evolutionarily conserved mechanism for initiating parasympathetic regulation during stress recovery. It argues that mastication is not merely a nutritional or behavioral response, but a brainstem-mediated sensorimotor signal that facilitates autonomic transition from sympathetic arousal toward parasympathetic recovery.

The hypothesis is grounded in cranial nerve neuroanatomy, particularly the trigeminal (V), glossopharyngeal (IX), facial (VII), and hypoglossal (XII) nerves, which converge in brainstem regions such as the nucleus tractus solitarius and broader central autonomic network. These structures are implicated in regulating cardiovascular, respiratory, and visceral states. The paper synthesizes evidence from neurophysiology, stress research, and evolutionary biology to propose that chewing may function as a transitional regulatory behavior rather than a primary stress inhibitor.

From an evolutionary perspective, oral-motor behaviors such as suckling, gnawing, and non-nutritive chewing are highly conserved and appear to play a role in stress modulation across mammalian species. The manuscript extends this framework to modern humans, proposing that contemporary stress-eating behaviors may reflect the activation of this ancestral regulatory pathway, now often coupled with hyperpalatable foods that engage dopaminergic reward systems. This mismatch may contribute to compulsive eating patterns and broader metabolic dysregulation, including obesity.

The paper further explores implications for dentistry, neurodivergent populations, and sensory processing, suggesting that alterations in oral sensory input or chewing capacity may influence autonomic regulation and emotional state. It also highlights potential therapeutic applications of controlled mastication or oral sensory interventions for stress modulation and attention regulation.

Finally, the manuscript outlines directions for future empirical research, including neuroimaging, heart rate variability, and endocrine measures, to test whether orofacial activity can reliably influence autonomic state transitions. Overall, the work reframes chewing as a foundational but underrecognized component of embodied stress recovery systems, with implications spanning neuroscience, psychology, anthropology, nutrition, and clinical practice.