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Chewing Hard Materials Boosts Brain Antioxidants and Enhances Cognitive Function

• Introduction: Chewing has been linked to improved cognitive function, possibly by increasing cerebral blood flow (CBF). This study investigates the role of glutathione (GSH), a key brain antioxidant, in this process. The anterior cingulate cortex (ACC) was the region of interest, pivotal for cognitive control.

• Hypotheses:

  • Brain GSH levels correlate with chewing hardness.
  • Chewing hardness influences the relationship between changes in GSH levels and cognitive function.

• Methods (Participants): 52 healthy university students were divided into two groups: gum-chewing (n=27) and wood-chewing (n=25). Groups were matched for age, sex, and education.

• Methods (Neuropsychological Measurement): The Korean Repeatable Battery for the Assessment of Neuropsychological State (K-RBANS) was used to assess cognitive function.

• Methods (Chewing Task): Participants chewed either paraffin wax gum or a wood stick for 5 minutes, alternating 30 seconds of chewing and 30 seconds of rest, focusing on the right molar region at 1 Hz.

• Methods (MRS Data Measurement): Brain GSH levels in the ACC were measured using a GSH-edited MEGA-PRESS sequence on a 3.0 T MRI scanner before and after the chewing task.

• Methods (MRS Data Processing): LCModel was used to quantify metabolite levels, including GSH, from the MRS data. Quality control involved Cramér-Rao lower bounds (CRLB) to ensure reliable measurements (GSH CRLB < 20%).

• Results (Demographic Characteristics and Neuropsychological Analysis): No significant differences in demographics or K-RBANS scores were found between the gum and wood-chewing groups at baseline.

• Results (Metabolites Quantification by MRS using MEGA-PRESS):

  • GSH levels significantly increased after chewing in the wood-chewing group (p = 0.007), but not in the gum-chewing group (p = 0.505).
  • Other metabolites (tNAA, tCr, tCho, MI) did not show significant changes.

• Results (Relationship between GSH levels and neuropsychological measurements):

  • In the wood-chewing group, increased GSH levels were positively correlated with immediate memory (r = 0.520, p = 0.008) and story memory (r = 0.439, p = 0.028) scores.
  • No such correlations were observed in the gum-chewing group.

• Discussion:

  • The study provides the first evidence that mastication can increase brain antioxidant (GSH) levels in humans.
  • Increased GSH may protect the brain from oxidative stress, which is linked to cognitive decline and neurodegenerative diseases.
  • Increased cerebral blood flow (CBF) from chewing could stimulate GSH synthesis.
  • Chewing hard materials might be a practical way to boost brain GSH levels, as direct GSH administration is ineffective due to degradation.

• Limitations: The narrow age range of participants (20-30 years), relatively small sample size. Future research is required to generalize the finding. Only focused on the ACC, limited chewing time (5 min), and lack of objective chewing hardness measurement.

• Conclusion: Chewing moderately hard materials increases brain GSH levels, and this increase is associated with improved memory function. This suggests that consuming harder foods may be more effective in enhancing brain antioxidant defenses.

• Data Availability: The raw data are available from the authors.

• Ethics Statement: The study was approved by the Institutional Review Board of Kyungpook National University Dental Hospital, and all participants provided informed consent.