Recent studies, though they differ in technique, focus on the effect on the brain of polyphenol compounds in green tea. Though the studies used green tea extracts, notably a polyphenol compound called EGCG, experts assure that similar benefits can be gained by sipping tea.
Swiss researchers used functional magnetic resonance imaging (fMRI) to watch the brains of 12 healthy volunteers perform tasks measuring “working memory.” Working memory allows the brain to simultaneously store and process information during the complex cognitive tasks of language comprehension, learning and reasoning.
Participants’ brains were scanned after subjects had consumed two beverages containing different doses of green tea extract and a placebo drink.
Compared to the effect of the placebo, the beverages with green tea extract were associated with increased activity in the working-memory processing section of the brain; activity was greater with the higher dose of green-tea extract.
Chinese researchers used mice to test the brain-cell effects of the EGCG in green tea by adding an EGCG solution to brain cells from the hippocampus of white mice.
The hippocampus produces nerve cells (neurogenesis) in adult brains and is important to brain plasticity—the ability of the brain to change in response to new inputs. Production decreases with age, a dropoff associated with neurological disorders and cognitive decline.
When researchers injected EGCG into mice, the number of cells associated with neurogenesis increased substantially, and their maze-navigating performance improved considerably, a sign of increased spatial cognition.
Sources: Tufts University Health & Nutrition Letter, June 2013 Swiss study published in European Journal of Clinical Nutrition Chinese study published in Molecular Nutrition & Food Research