M. Jackson Group Update – December 2019 – Positive Effects of Tea on the Brain

The new issue of Aging includes a study: “Habitual tea drinking modulates brain efficiency: evidence from brain connectivity evaluation.”
The authors are Junhua Li 1, 2, 3 ,  Rafael Romero-Garcia 4 ,  John Suckling 4 , & Li Feng.
Here’s an excerpt from the Introduction:
[begin excerpts]
A growing literature has demonstrated that tea intake is beneficial to human health, including mood improvement (e.g., anti-stress) [2–4], risk reduction of cognitive decline [5–8], cardiovascular disease prevention [9], lower cancer incidence [10, 11], reduced mortality [12, 13].
These benefits of tea are derived primarily from the effects of its constituents: catechin, L-theanine, and caffeine. In…studies [14–16], catechin has been found to be beneficial to cognitive health, showing enhancements in memory recognition and working memory performance compared to the intake of placebo [14].
Kimura et al. discovered that L-theanine plays a positive role in anti-stress by reducing stress-induced heart rate and salivary immunoglobulin A (s-lgA) during a stressed mental arithmetic task [3].
The beneficial effect of caffeine on cognitive functioning was reported at least two decades ago [17] and replicated by recent studies [18, 19]. 

Although individual constituents of tea have been related to the roles of maintaining cognitive abilities and preventing cognitive decline, a study with behavioural and neurophysiological measures showed that there was a degraded effect or no effect when a constituent was administered alone and a significant effect was observed only when constituents were combined [20].
The superior effect of the constituent combination was also demonstrated in a comparative experiment [21] that suggested that tea itself should be administered instead of tea extracts; a review of tea effects on the prevention of Alzheimer’s disease (AD) [22], found that the neuroprotective role of herbal tea was apparent in eight out of nine studies.
It is worth noting that the majority of studies thus far have evaluated tea effects from the perspective of neurocognitive and neuropsychological measures, with direct measurement of brain structure or function less-well represented in the extant literature (see a recent summary in [23]). In a double-blind, placebo-controlled, crossover study with near-infrared spectroscopy measure, cerebral blood flow in the frontal cortex was reduced by oral tea administration [24]. This change of regional brain activity was also observed by EEG in a study, showing that higher theta, alpha, and beta oscillations were associated with tea consumption in the frontal and medial frontal gyri [25]. These studies focusing on brain regional alterations did not ascertain tea effects on interregional interactions at the level of the entire brain.
[end excerpts]
Another excerpt: “In this study, we comprehensively explored brain connectivity with both global and regional metrics derived from structural and functional imaging to unveil putative differential connectivity organizations between tea drinking group and non-tea drinking group. In addition, we focused on interregional connectivity within the default mode network (DMN) because previous studies have suggested that it is predominantly involved in cognitive disease [31] and normal ageing [32]. Moreover, according to our prior investigation of hemispheric asymmetry, leftward asymmetry in structural connectivity is associated with brain ageing [33]. Therefore, hemispheric asymmetries in connectivity were also included to test the effects of tea drinking. We hypothesized that: (1) habitual tea drinking has positive effects on brain organization and gives rise to greater efficiency in functional and structural connectivities; (2) tea intake leads to less leftward asymmetry in structural connectivity; (3) tea drinking is associated with connective strength alterations of functional and structural connectivities in the DMN.”
Another excerpt: “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.”
Here’s how it concludes: “In summary, our study comprehensively investigated the effects of tea drinking on brain connectivity at both global and regional scales using multi-modal imaging data (i.e., functional and structural imaging) and provided the first compelling evidence that tea drinking positively contributes to brain structure making network organization more efficient.  Our study suggests that tea drinking is effective in preventing (slowing) or ameliorating cognitive decline and that tea drinking might be a simple lifestyle choice that benefits brain health.”
 
“Let food be thy medicine and medicine be thy food.”
—Hippocrates

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