Is there anything us Brits cherish as dearly as a cuppa? According to the UK Tea Council, the British are the largest per capita tea consumers in the world, and as a nation we get through a staggering 165 million cups a day. As such, tea is enshrined in our culture, in fact, so hallowed is it that even our employers grant us respite from work for a 'tea break'. As an avid tea drinker myself, recent research about the effects of green tea on the brain got me musing about our penchant for tea, and whether it's time to take a leaf from the Orient, where green tea, rather than black tea, is the beverage of choice.
Both types of tea are made from the same Camellia sinensis leaves, the difference solely relating to their processing, with the leaves used for black tea undergoing oxidation by fermentation, whereas those used for green tea are simply lightly steamed and dried. Importantly, this process significantly alters the pharmacological properties of tea and it is a group of plant compounds called catechins (the subject of intense interest for their health benefits) which are altered, so whereas green tea boasts a 30-40% catechin content, this shrinks to a mere 3-10% for black tea.
A piece of research just published studied the effects of a major type of catechin found in green tea, epigallocatechin-3-gallate (EGCG), and found that it promoted the generation of cells in the hippocampus (the part of the brain that processes information relating to short-term and long-term memory) in both lab tests and mice [1]. The mice, imbibed with EGCG, performed better on tests that indicated the green tea compound improved learning and memory. It suggests that this constituent of green tea, by stimulating the growth and development of important neural cells, could give a brainy boost and be a candidate for improving cognitive function and even preventing memory loss and neurodegeneration.
We've all heard the idiom about 'brain food', but could green tea represent a 'brain drink'? Of course, in the rush of enthusiasm about research such as this, we won't slip on the classic banana skin and start extrapolating wildly about the miracle benefits of green tea for brain health simply based on cell culture or animal studies alone, but it does prompt a wider look at what other research has to say on the matter.
In another recent study, researchers used MRI technology to show that drinking a green tea enriched beverage increased activation in the dorsolateral prefrontal cortex, a part of the brain linked to working memory [2]. And this seems to fit with a growing body of evidence to show that flavonoid-rich foods/beverages (and here we wouldn't just include green tea, but also berry fruits and cocoa) have the potential to slow the progression of neurodegenerative diseases (such as Alzheimer's disease) and to promote cognitive performance [3].
And if that's not enough to whet your appetite for green tea, then other more widely publicized health benefits attributed to green tea drinking include protection against cardiovascular disease, potential effects on warding off certain cancers, benefits for oral health, and modest benefits for weight loss too [4].
I'm not for a minute knocking black tea. As far as beverages go, it's a pretty healthy choice in its own right, proffering a bountiful source of health enhancing flavonoids. But those looking for the edge when it comes to their health, and specifically giving their grey matter a boost, might do well to go green.
[1] Wang Y et al (2012) Green tea epigallocatechin-3-gallate (EGCG) promotes neural progenitor cell proliferation and sonic hedgehog pathway activation during adult hippocampal neurogenesis. Mol Nutr Food Res 56(8):1292-303
[2] Borgwardt S et al (2012) Neural effects of green tea extract on dorsolateral prefrontal cortex Eur J Clin Nutr 2012 Aug 29 [Epub ahead of print]
[3] Williams RJ, Spencer JP (2012) Flavonoids, cognition, and dementia: actions, mechanisms, and potential therapeutic utility for Alzheimer disease. Free Radic Biol Med. 52(1):35-45.
[4] Mak JC (2012) Potential role of green tea catechins in various disease therapies: progress and promise. Clin Exp Pharmacol Physiol 39(3):265-73