Effect of chewing hard material on boosting brain antioxidant levels and enhancing cognitive function

Abstract

Introduction: Chewing has been reported to enhance cognitive function through the increase in cerebral blood flow. However, the mechanisms linking cerebral blood flow increase to metabolic changes in the brain affecting cognition remain unclear. We hypothesized that glutathione (GSH) plays a pivotal role in these mechanisms. Therefore, this study aimed to investigate changes in brain GSH levels following chewing and their association with cognitive function in healthy young adults.

Methods: A total of 52 university students were recruited, and the Korean version of the Repeatable Battery for the Assessment of Neuropsychological Status was used for the neurocognitive evaluations. Brain GSH levels following chewing gum or wood blocks were measured using MEscher-GArwood Point RESolved Spectroscopy (MEGA-PRESS) sequence, and their relevance to neurocognitive evaluation results was investigated.

Results: Chewing significantly increased brain GSH concentration, particularly in the wood-chewing group compared to the gum-chewing group, as observed in the anterior cingulate cortex. Furthermore, the rise in GSH concentration in the wood-chewing group was positively correlated with memory function.

Conclusion: Chewing moderately hard material elevates brain antioxidant levels such as GSH, potentially influencing cognitive function.

Keywords: brain activation; cognitive function; functional magnetic resonance imaging (fMRI); hardness; mastication; motor function.

Figure 1

The representative GSH-edited spectra of mastication before and after from anterior cingulate cortex (ACC) by MEGA-PRESS method. Editing on (Red line) and off (Blue line) spectra were aligned and differenced. The difference spectra and spectral fitting results were described as the yellow thick and thin lines, respectively. Because GSH signal in the MR spectra is overlapped with other metabolite signals, the spectral editing technique with edit-on and edit-off MRS sequences was employed to give only GSH signal as shown in the bottom (gray line). The purple vertical lines indicate the peaks of NAA (2.01 ppm), GSH (2.95 ppm), Cr (3.03 ppm), Cho (3.21 ppm).

Figure 2

The changes of GSH concentrations in each group. The GSH concentrations (Cramér-Rao lower bound) were 1.23 mM (9%), 1.28 mM (8%) in the gum group, and 1.22 mM (8%), 1.37 mM (8%) in the wood group in mastication before and after, respectively. (^*p < 0.01). The gum group showed no significant change before and after gum chewing but the wood group showed statistically significant increase in GSH concentration after wood chewing compared to GSH concentration before wood chewing.

Figure 3

Correlation between the changes of GSH concentrations in anterior cingulate cortex (ACC) and cognitive functions. Both correlations with immediate memory and story memory as cognitive function measure revealed that the gum chewing group did not show any significant correlations between the changes of GSH concentrations and immediate memory and story memory (p = 0.248 and p = 0.290 respectively). The wood chewing group however showed the significant positive correlations between the changes of GSH concentrations and immediate memory and story memory (p = 0.008 and p = 0.028 respectively). These results therefore suggest that the increase of GSH concentration by wood chewing increase the cognitive functioning in wood chewing group.