People who regularly drink green tea may
have a lesser risk of mental decline as they grow older,
researchers have found.
Their study, of more than 1,000
Japanese adults in their 70s and beyond, found that the
more green tea men and women drank, the lower their odds
of having cognitive impairment.
The findings build on evidence from lab experiments showing
that certain compounds in green tea may protect brain
cells from the damaging processes that mark conditions
like Alzheimer's and Parkinson's disease.
But while those studies were carried out in animals and
test tubes, the new research appears to be the first to
find a lower risk of mental decline among green-tea drinkers,
according to the study authors.
They speculate that the possible protective effects of
green tea may help explain Japan's lower rate of dementia,
particularly Alzheimer's disease,
compared with Europe and North America.
Dr. Shinichi Kuriyama and colleagues at Tohoku University
Graduate School of Medicine report the findings in the
current issue of the American Journal of Clinical Nutrition.
The study included 1,003 adults age 70 and older who
completed detailed questionnaires on their diets over
the previous month, as well as their overall physical
health and lifestyle habits. They also completed a standard
test of cognitive functions such as memory, attention
and language use.
The researchers found that older adults who drank two
or more cups of green tea per day were about half as likely
to show cognitive impairment as those who drank three
cups or less each week. Men and women who averaged one
cup per day fell somewhere in between.
The connection between green tea and mental function
persisted when the researchers accounted for overall diet
and factors such as smoking and exercise habits.
However, the findings cannot demonstrate a cause-and-effect
relationship.
The study was observational, not a controlled experiment,
and there may be something about green-tea drinkers that
explains the link between the beverage and sharper mental
function, Kuriyama stated.
For example, healthier, more active individuals may simply
drink more green tea -- which, in Japan, is often consumed
in social settings.
"We think that the potential protective effects of green
tea should be confirmed in further studies," Kuriyama
said.
Given the high prevalence and heavy burden of dementia,
the researchers conclude, any benefit of drinking green
tea could have a "considerable" public health impact.
SOURCE: American Journal of Clinical Nutrition, February
2006.
