Whether served hot, cold, sweet, or bitter, tea is a ubiquitous drink worldwide that has held its own against the recent uprising of coffee culture. And now, a comprehensive brain study has found that long-term tea drinkers may also enjoy added cognitive benefits from the drink.
The study, published in June in the journal Aging, describes the results of a study conducted between a group of non-tea drinkers and a group of tea drinkers. By looking at the global and regional structure and functionality of the participants’ brains, researchers determined a set of noticeable differences. These included a greater efficiency of functional and structural connectivities among regions for tea drinkers, as well as less asymmetry in the structural connections between hemispheres, which the authors write both reflect a younger cognitive age and possible slowing of cognitive decline.
The authors recruited participants who were all around the same age and education level who either had a strong record of consistent tea drinking or a strong record of abstaining. On average, the participants were in their early 70s, and both groups had significantly more female participants than males. To determine exactly how much of a tea drinker each participant was, they self-reported their tea intake on a scale from 1 to 6, with 1 being “never or rarely” and 6 being “greater than or equal to 3 times a day.” And for the purposes of the study, “tea” meant green tea, oolong tea, or black tea — not herbal tea.
All in all, the authors write that these restrictions gave them a relatively small sample size: 15 tea drinkers and 21 non-tea drinkers. However, they note that this sample size was still larger than previous studies that looked at similar metrics.
As for what the study found, both the so-called efficiency and symmetry of the brains of tea drinkers point toward slower cognitive decline, say the researchers.
The authors say “efficiency” refers to an easier and faster communication of information among brain regions, essentially resulting in a snappier brain. As for symmetry, non-tea drinkers showed a leftward asymmetry of brain connectivity, falling into a structural pattern that is more associated with an aging brain. Tea drinkers, on the other hand, demonstrated more symmetry in their connections, which researchers say more closely resembled the connectivity of a middle-aged brain.
“Collectively, previous studies have suggested a U-shaped developmental trajectory in hemispheric asymmetry … across the lifespan from childhood to middle age to old age,” the authors write. “Taken together, the suppression of leftward asymmetry in structural connectivity suggests that tea intake could slow age-related alterations towards leftward asymmetry and retain a pattern more similar to that of the middle age.”
However, while the researchers did observe an efficiency increase in both structural and functional connectivity, they say that this didn’t necessarily translate to overall enhanced functional connectivity between the two hemispheres. The authors write that these results may suggest that structural systems are more easily altered.
“These results together allow speculation that structural global metrics are more sensitive to subtle alterations in the brain compared to functional global metrics in terms of overall connectivity at the network scale,” they write.
As for what this means for us, the researchers write that picking up a tea-drinking habit could be a good way to not only benefit from previously reported health benefits, such as cardiovascular and mood benefits, but also to potentially slow age-related cognitive decline.
Abstract: The majority of tea studies have relied on neuropsychological measures, and much fewer on neuroimaging measures, especially for interregional connections. To date, there has been no exploration of the effect of tea on system-level brain networks. We recruited healthy older participants to two groups according to their history of tea drinking frequency and investigated both functional and structural networks to reveal the role of tea drinking on brain organization. The results showed that tea drinking gave rise to the more efficient structural organization, but had no significant beneficial effect on the global functional organization. The suppression of hemispheric asymmetry in the structural connectivity network was observed as a result of tea drinking. We did not observe any significant effects of tea drinking on the hemispheric asymmetry of the functional connectivity network. In addition, functional connectivity strength within the default mode network (DMN) was greater for the tea-drinking group, and coexistence of increasing and decreasing connective strengths was observed in the structural connectivity of the DMN. Our study offers the first evidence of the positive contribution of tea drinking to brain structure and suggests a protective effect on age-related decline in brain organisation.