Chewing Wood Could Give Your Brain an Unexpected Boost

Maybe dogs who chew sticks are on to something. We don't necessarily have to chomp with a canine's zeal, but the basic concept – safely gnawing some hard, durable material – might be worth considering.

According to a new study, chewing on a hard substance like wood can boost levels of a naturally occurring antioxidant in the human brain, which in turn might improve a person's memory.

Many people chew gum, of course, which is softer but arguably more palatable than wood (and avoids tongue splinters). Previous research has shown chewing gum can, in fact, significantly increase brain activity, as the authors of the new study note.

Getting the brain's blood supply pumping seems to improve a variety of cognitive functions, it seems. Curiously, clinical evidence also suggests people who find chewing a challenge also tend to have lower cognitive function and higher mental impairment.

It remains unclear, though, what specific metabolic changes associated with cognition might occur following a boost in cerebral blood flow.

In the new study, researchers investigated one possible explanation involving oxidative stress in neurological tissues, which is already believed to play a pivotal role in the decline of cognitive function.

Several metabolic processes produce harmful molecules known as reactive oxygen species, which can cause cumulative oxidative damage in the human brain. One of the brain's best defenses against oxidative stress is an antioxidant called glutathione (GSH), which holds many important jobs throughout the body, including protecting neurons from reactive oxygen species.

Hoping to shed light on the cognitive effects of chewing, the researchers designed the new study to explore the potential role of glutathione. Despite its importance in the brain, they note, the relationship between glutathione levels and mastication has drawn little attention until now.

They recruited 52 healthy university students from Daegu, South Korea, and divided them into two groups. One group of 27 subjects was given paraffin wax gum to chew; a second group of 25 was asked to chew on wooden medical tongue depressors.

Subjects chewed their assigned substance for five minutes, while researchers used magnetic resonance spectroscopy to measure glutathione levels in their anterior cingulate cortex – a key brain region for cognitive control – before and after chewing. All subjects also took a cognitive test before and after the activity.

Chewing significantly boosted glutathione levels in subjects' anterior cingulate cortices, especially in the wood-chewing group compared with the gum-chewing group, the researchers report.

Combined with results from the cognitive tests, the rise in glutathione concentration correlated positively with memory function. In other words, those who chewed wood and had larger glutathione boosts also performed better on the tests.

"To the best of our knowledge, this is the first report indicating that mastication can alter the level of antioxidants in the human brain, and that an increase in brain antioxidant levels is associated with cognitive function," the researchers write.

More research will still be needed to back up these findings, the study's authors add, with larger sample sizes, broader demographics, and assessment of different brain regions important focusses for subsequent studies.

While wood seemed to confer more benefit than paraffin wax gum, this study also only tested two substances being chewed for five minutes. Future research might also investigate a wider range of materials and chewing durations.

These findings alone may not be sufficient evidence to recommend chewing wood for better memory, but they do provide a compelling hint. And it would be good news if chewing wood does have this effect, the researchers write, given the challenge of managing glutathione levels in the brain.

"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," the researchers write.

The study was published in Frontiers in Systems Neuroscience.