Compared to people who drank less than one cup per day, at least five cups of the green tea was associated with a 33% reduction in functional disability, according to a study published in the American Journal of Clinical Nutrition.
Functional disability is anything that limits a person's ability to do physical activity, is a mental illness, or that requires long-term care. In the context of the new study, this is mostly linked to cardiovascular disease and stroke, reduced mental performance, and osteoporosis.
“To our knowledge, this is the first reported study to have proved the relation between green tea consumption and incident risk of functional disability,” wrote researchers from the Tohoku University Graduate School of Medicine.
The majority of science on tea has looked at green tea, with benefits reported for 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.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
The new study adds to the impressive body of evidence supporting the potential health benefits of the beverage.
The Japanese researchers analyzed data from 13,988 over 65 year olds. A questionnaire was used to assess green tea intake and other dietary and lifestyle factors.
After following the people for three years, the researchers noted that drinking one to two cups of green tea per day was associated with a 10% reduction in the risk of functional disability, compared to people who drank less than one cup per day.
Consuming three to four cups per day was associated with a 25% reduction in functional disability, while over five cups per day was associated with a 33% reduction.
“As [previously] noted, green tea consumption was associated with lower risks of stroke, dementia, and bone fracture,” wrote the researchers. “This survey reported that the third most common cause of functional disability was ‘frailty’ (13.6%), which is mostly associated with sarcopenia and lower muscle strength.
“More recently, green tea polyphenols have been reported to improve leg strength. Furthermore, depression is also known to pose a risk of functional disability in the elderly. Our previous study indicated that green tea consumption was associated with a lower risk of depression.
“All of these findings provide a biological basis for the effect of green tea in preventing or postponing the onset of functional disability in the elderly.”
The researchers called for clinical trials to confirm the potential benefits of consuming green tea on a lower risk of functional disability.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.111.023200
“Green tea consumption and the risk of incident functional disability in elderly Japanese: the Ohsaki Cohort 2006 Study”
Authors: Y. Tomata, M. Kakizaki, N. Nakaya, T. Tsuboya, T. Sone, S. Kuriyama, A. Hozawa, I. Tsuji