|Clinical study sees green tea boosting brain areas associated with working memory; mouse study affirms the effect
By Craig Weatherby
A Swiss scientific team gives us the first look inside the brains of green tea drinkers.
It’s been pretty well proven that drinking green tea will not prevent Alzheimer’s or dementia.
But most of us will be happy with any food, drink, or dietary supplement that helps maintain memory function as we reach senior status.
And the Swiss team’s small fMRI study suggests that green tea antioxidants may benefit a part of the brain associated with “working” memory.
Working memory vs. short-term memory
Working memory is not the same as short term memory, which is the capacity for retaining a small amount of information for up to one minute.
Instead, the brain’s working memory system holds multiple bits of information needed for reasoning and comprehension for longer periods, and keeps them available for further processing.
Working memory enables tasks that require directed action toward a goal, despite distracting sensory inputs or mental processes.
It involves the brain’s “executive” control of short-term memories, and enables integration, processing, disposal, and retrieval of information.
Our capacity for working memory increases gradually over childhood … and declines as we age.
Swiss study sees green tea boosting working memory regions
Previous studies have indicated that the antioxidant polyphenols green tea – and, to a lesser extent, the phenols in black tea – might benefit memory.
Animal studies suggest that green tea works in multiple ways to benefit brain health, including reduction of oxidation and inflammation (Dimpfel W et al. 2007; Mandel SA et al. 2008; Kakuda T 2011; Andrade JP, Assunção M 2012; Biasibetti R et al. 2012; Wu KJ et al. 2012; Lee YJ et al. 2012).
A new double-blind, controlled trial from Switzerland’s University Hospital Basel is one of the few human studies … and the first to use functional magnetic resonance imaging (fMRI) scans.
Professor Stefan Borgwardt’s team employed fMRI scans looked for changes in volunteers’ brains following the consumption of green tea extracts (Borgwardt S et al. 2012).
The Swiss group recruited 12 healthy volunteers to perform a working memory task after consuming 250 or 500 ml of a whey-based soft drink. (Whey is milk protein.)
Half got a drink with added green tea extract, and the others got the same drink without tea extract (Rivella AG, Switzerland).
The fMRI scans showed no significant overall changes in the whole brain … but consumption of the green tea extract was associated with increased activation in the dorsolateral prefrontal cortex or DL-PFC.
The DL-PFC region is involved in working memory and considered critical to the integration of sensory and mnemonic (memory-triggering) information and the regulation of intellectual functions.
Significantly, higher doses of green tea extract produced greater activation of the DL-PFC region.
As the Swiss team concluded, “… green tea extract enhances the engagement of brain regions that mediate working memory processing.” (Borgwardt S et al. 2012)
Mouse study affirms green tea’s memory effects
Green tea is one of few sources of a polyphenol compound called epigallocatechin-3 gallate (EGCG).
(Cocoa is another rich source, though it has less EGCG that green tea does, and greater amounts of related catechin compounds.)
Prior research indicates that EGCG might boost memory and brain functions … and could perhaps even help prevent or ameliorate some neurodegenerative diseases.
Supporting those ideas, a mouse study from China shows that EGCG from tea boosted the production of brain cells important to memory and “spatial” learning (Wang Y et al. 2012).
The research team found that dietary EGCG improved learning and memory in mice by improving object recognition and spatial memory.
They hypothesized that EGCG improves cognitive function by boosting the generation of brain cells – a process known as neurogenesis – in brain areas involved in memory, such as the hippocampus.
In a test tube study, the Chinese group found that EGCG boosted the production of neural progenitor cells in tissue from the mouse hippocampus. (Like stem cells, progenitor cells can differentiate into various types of cells.)
Specifically, EGCG promoted the growth of progenitor cells in the hippocampus.
The researchers then gave mice EGCG from green tea to see whether it would improve the animals’ memory or spatial learning.
They ran tests on two groups of mice, one which had imbibed EGCG, and a control group.
First, the mice were trained for three days to find a visible platform in their maze. Then they were trained for seven days to find a hidden platform.
The mice given EGCG required less time to find the hidden platform – suggesting that the compound enhances learning and memory by improving object recognition and spatial memory.
As the scientists wrote, “We have shown that the organic chemical EGCG acts directly to increase the production of neural progenitor cells, both in glass tests and in mice.
This helps us to understand the potential for EGCG, and green tea which contains it, to help combat degenerative diseases and memory loss.” (Wang Y et al. 2012)
So drink up … if you can remember to do it!
Andrade JP, Assunção M. Protective effects of chronic green tea consumption on age-related neurodegeneration. Curr Pharm Des. 2012;18(1):4-14. Review.
Biasibetti R, Tramontina AC, Costa AP, Dutra MF, Quincozes-Santos A, Nardin P, Bernardi CL, Wartchow KM, Lunardi PS, Gonçalves CA. Green tea (-)epigallocatechin-3-gallate reverses oxidative stress and reduces acetylcholinesterase activity in a streptozotocin-induced model of dementia. Behav Brain Res. 2012 Sep 1. [Epub ahead of print]
Borgwardt S, Hammann F, Scheffler K, Kreuter M, Drewe J, Beglinger C. Neural effects of green tea extract on dorsolateral prefrontal cortex. Eur J Clin Nutr. 2012 Aug 29. doi: 10.1038/ejcn.2012.105. [Epub ahead of print]
Dimpfel W, Kler A, Kriesl E, Lehnfeld R, Keplinger-Dimpfel IK. Source density analysis of the human EEG after ingestion of a drink containing decaffeinated extract of green tea enriched with L-theanine and theogallin. Nutr Neurosci. 2007 Jun-Aug;10(3-4):169-80
Kakuda T. Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction. Pharmacol Res. 2011 Aug;64(2):162-8. Epub 2011 Apr 6. Review.
Lee YJ, Choi DY, Yun YP, Han SB, Oh KW, Hong JT. Epigallocatechin-3-gallate prevents systemic inflammation-induced memory deficiency and amyloidogenesis via its anti-neuroinflammatory properties. J Nutr Biochem. 2012 Sep 5. [Epub ahead of print]
Mandel SA, Amit T, Kalfon L, Reznichenko L, Weinreb O, Youdim MB. Cell signaling pathways and iron chelation in the neurorestorative activity of green tea polyphenols: special reference to epigallocatechin gallate (EGCG). J Alzheimers Dis. 2008 Oct;15(2):211-22. Review.
Wang Y, Li M, Xu X, Song M, Tao H, Bai Y. Green tea epigallocatechin-3-gallate (EGCG) promotes neural progenitor cell proliferation and sonic hedgehog pathway activation during adult hippocampal neurogenesis. Mol Nutr Food Res. 2012 Aug;56(8):1292-303. doi: 10.1002/mnfr.201200035. Epub 2012 Jun 13.
Wu KJ, Hsieh MT, Wu CR, Wood WG, Chen YF. Green Tea Extract Ameliorates Learning and Memory Deficits in Ischemic Rats via Its Active Component Polyphenol Epigallocatechin-3-gallate by Modulation of Oxidative Stress and Neuroinflammation. Evid Based Complement Alternat Med. 2012;2012:163106. Epub 2012 Aug 2.