Tea's brain health benefit link gets more support
like Alzheimer's, says a new study, adding yet more support to the
benefits of tea extract on brain health.
"We looked at the protective effects of two tea extracts and their main constituents, called catechins, on dying nerve cells," explained senior author Rémi Quirion from Douglas Hospital Research Centre, Quebec.
The research, published in the European Journal of Neuroscience (Vol. 23, pp. 55-64), claims to be the first to show beneficial effects of both green and black tea on cell cultures treated with amyloid proteins. Amyloid proteins are associated with the onset of Alzheimer's disease, the most common form of dementia and currently affects over 13 million people worldwide.
The direct and indirect cost of Alzheimer care is over $100 billion (€81 billion) in the US alone. The direct cost of Alzheimer care in the UK was estimated at £15 billion (€22 billion).
Although the mechanism of Alzheimer's is not clear, more support is gathering for the build-up of plaque from amyloid deposits. The deposits are associated with an increase in brain cell damage and death from oxidative stress.
The researchers used rat hippocampal cells as models for human cells, and found that addition of the beta-amyloid protein was toxic and killed the cells.
However, both green and black tea extracts, with concentration levels between five and 25 micrograms per millilitre, were found protective activity against the effects of the amyloid protein.
"These effects were shared by [tea extracts] gallic acid, epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), the former being the most potent flavon-3-ol. In contrast, epicatechin and epigallocatechin (ECG) were ineffective in the same range of concentrations," reported lead author Stéphanie Bastianetto.
Both EGCG and gallic acid were found to stop the amyloid aggregation, which could result in plaque formation, and also stopped potentially poisonous amyloid derivatives that would be diffusible across cell membranes.
"These data support the hypothesis that not only green but also black teas may reduce age-related neurodegenerative diseases, such as Alzheimer's disease," concluded Bastianetto.
It is known that the catechins can be extracted from both green and black teas, but the yield from the unfermented green tea leaf is significantly higher. Green tea is said to contains about 70 mg catechins per 100 mL, whereas black tea contains only about 15 mg per 100 mL.
This is further support for both the tea market and the tea extract market. European demand for tea extracts is currently surging, having reached 500 metric tonnes by 2003.
The global tea market is worth about €790 (£540, $941) million. Green tea accounts for about 20 per cent of total global production, while black tea (green tea that has been oxidized by fermentation) accounts for about 78 per cent.
