Magnetic resonance imaging (MRI) showed that a whey-based soft drink containing green tea was associated with increased activation in the dorsolateral prefrontal cortex, a section of the human brain linked to working memory.
The study, published in the European Journal of Clinical Nutrition, adds to the long list of potential health benefits of green tea and its extracts, including reducing the risk of Alzheimer's and certain cancers, improving cardiovascular and oral health, as well as aiding in weight management.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
While previous studies have reported potential benefits for green tea on memory, the new study, led by Professor Stefan Borgwardt from the University Hospital Basel in Switzerland, is said to be the first to use functional magnetic resonance imaging to observe changes in the brain following the consumption of green tea extracts.
The researchers recruited 12 healthy volunteers and asked them to perform a working memory task after consuming 250 or 500 ml of a whey-based soft drink with or without green tea extract (Rivella AG, Switzerland) in a double-blind, controlled repeated measures within-subject trial.
While analysis of the whole brain revealed no significant changes, further analysis showed that consumption of the green tea extract was associated with increased activation in the dorsolateral prefrontal cortex, report Prof Borgwardt and his co-workers.
In addition, the effects were linked to the doses consumed, with higher doses producing greater activation.
“This is the first neuroimaging study implicating that functional neuroimaging methods provide a means of examining how green tea extract acts on the brain and that green tea extract enhances the engagement of brain regions that mediate working memory processing,” they concluded.
Source: European Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1038/ejcn.2012.105
“Neural effects of green tea extract on dorsolateral prefrontal cortex”
Authors: S Borgwardt, F Hammann, K Scheffler, M Kreuter, J Drewe, C Beglinger