Chewing on moderately hard foods, like wood, might do more than just break down your lunch; new research suggests it could actually boost brainpower by increasing levels of a natural antioxidant, which in turn may improve memory. A recent study published in Frontiers in Systems Neuroscience explored how chewing different materials affects the brain and found that chewing on wood, compared to chewing gum, led to a significant increase in a brain antioxidant called glutathione.
Previous research has suggested that the act of chewing can influence brain activity and blood flow. This is important because the brain requires a constant supply of oxygen and nutrients to function properly, and blood flow is the delivery system for these essential resources. Some studies have even shown that people with chewing difficulties tend to experience poorer cognitive abilities. However, exactly what metabolic changes occur in the brain when chewing improves blood flow has remained unclear.
One area of interest is oxidative stress in the brain. Oxidative stress is essentially damage to brain cells caused by harmful molecules called reactive oxygen species. This kind of damage is thought to play a significant role in the decline of brain function as we age. The brain is especially vulnerable to oxidative stress because it uses a lot of oxygen and contains fats that are easily damaged. To protect itself, the brain uses antioxidants, and one of the most important is glutathione.
Glutathione acts like a bodyguard for brain cells, neutralizing harmful reactive oxygen species. Researchers in this study were curious if chewing, and specifically chewing materials of different hardness, could influence the levels of this protective antioxidant, glutathione, in the brain. They also wanted to see if any changes in glutathione were related to changes in thinking skills.
To investigate these questions, the researchers recruited 52 healthy university students in South Korea. They divided the students into two groups: one group would chew gum, and the other group would chew small wooden sticks, similar to popsicle sticks. The researchers made sure the groups were similar in age, gender, and education level.
Before the chewing began, and again after five minutes of chewing, the researchers used a special brain scanning technique called Magnetic Resonance Spectroscopy to measure the levels of glutathione in a specific area of the brain called the anterior cingulate cortex. This brain region is known to be important for cognitive control and thinking processes. Magnetic Resonance Spectroscopy is a non-invasive method that allows scientists to measure the concentration of different chemicals in the brain. The specific technique they used, called MEGA-PRESS, is particularly good at measuring glutathione.
During the chewing task, participants were positioned comfortably and instructed to chew for five minutes. To keep the chewing consistent, they were asked to chew on the right side of their mouth at a rate of once per second, alternating between 30 seconds of chewing and 30 seconds of rest. One group chewed paraffin wax gum, which is a standard type of chewing gum used in research. The other group chewed on wooden tongue depressors.
Both before and after the chewing session, all participants also completed a cognitive test called the Korean Repeatable Battery for the Assessment of Neuropsychological State. This test is designed to quickly assess different aspects of thinking skills, including memory, attention, language, and visual-spatial abilities. This allowed the researchers to see if there was any change in cognitive function related to the chewing.
After analyzing the data, the researchers found some interesting results. First, they looked at the glutathione levels in the anterior cingulate cortex before and after chewing. In the group that chewed wood, they observed a significant increase in glutathione levels after chewing compared to before. This means that chewing wood seemed to boost the amount of this important antioxidant in that brain region.
However, in the gum-chewing group, there was no significant change in glutathione levels after chewing. While there wasn’t a statistically significant difference in the change in glutathione levels between the gum and wood groups directly, the trend was clearly towards a greater increase in the wood-chewing group.
Next, the researchers examined the relationship between changes in glutathione levels and performance on the cognitive tests. They found that in the wood-chewing group, the increase in glutathione levels was positively related to scores on immediate memory and story memory tests. This means that participants who showed a larger increase in glutathione after chewing wood also tended to perform better on memory tasks.
Interestingly, this relationship was not found in the gum-chewing group. There was no link between changes in glutathione and memory performance for those who chewed gum. In essence, chewing wood seemed to both increase brain antioxidant levels and improve certain aspects of memory, and these two changes appeared to be connected.
But the study, like all research, has some limitations to consider. Firstly, the participants were all young, healthy university students in their twenties. It’s not clear if these findings would be the same in older adults or in people with health conditions. Future studies should include a wider range of ages to see if the effects of chewing on glutathione and cognition are consistent across the lifespan.
Secondly, the study focused on just one specific brain region, the anterior cingulate cortex. While this region is important for thinking, it would be beneficial to investigate other brain areas to get a more complete picture of how chewing affects the brain.
Thirdly, the chewing period was relatively short, only five minutes. It’s possible that longer chewing durations, or different patterns of chewing, could have different effects. Also, while the study compared gum and wood, these materials differ in more ways than just hardness. Texture and other properties could also play a role. Future research could explore a wider variety of chewing materials and try to objectively measure the hardness of what people are chewing.
“In summary, this study yielded two major findings. Firstly, the wood-chewing group experienced stimulated of brain [glutathione (GSH)] synthesis, leading to increased GSH levels in the brain,” the researchers concluded. “Secondly, correlation analysis indicated that the higher GSH levels in the wood-chewing group were associated with improved scores in cognitive measures. Since there are currently no drugs or established practices for boosting brain GSH levels, our findings suggest that chewing moderately hard material could serve as an effective practice for increasing GSH levels in the brain. Based on these results, consuming harder foods might prove more effective in enhancing brain antioxidant defenses through elevated GSH levels.”
The study, “Effect of Chewing Hard Material on Boosting Brain Antioxidant Levels and Enhancing Cognitive Function,” was authored by Seungho Kim, Ji-Hye Kim, Hansol Lee, Sung Ho Jang, Ralph Noeske, Changho Choi, Yongmin Chang, and Youn-Hee Choi.
