Wednesday June 8 2016
Evidence suggests green tea can improve cognitive functions
"Down's syndrome can be treated with green tea," says The Daily Telegraph, reporting on a study that looked at the effect of a chemical extract on learning difficulties.
A Spanish study found some improvement in thinking abilities among people with Down's syndrome who took a supplement of green tea extract, and also had training, for a year.
The study involved comparing the effects of the extract – gallocatechin-3-gallate (EGCG) – on cognitive abilities compared with a dummy treatment (placebo).
The study gave 43 adults with Down's EGCG and compared them with 41 adults with Down's given a placebo.
The researchers used 24 cognitive tests. They found improvements in three of the tests for the extract group.
These tests looked at visual memory, the ability to control inhibitions when instructed to, and the ability to carry out everyday living tasks. Results for the other 21 tests were not significantly different between the groups.
Brain scans of 10 people from each group seemed to show more nerve cell connectivity in the group who took the extract.
However, too few people were given brain scans for us to be sure this result is not down to chance.
While a few cups of green tea a day is unlikely to cause any problems, experts have warned that people living with Down's syndrome, or their carers, should not "self-medicate" with green tea extract.
Different varieties contain different concentrations of EGCG, which may affect the heart at some concentrations.
This research is certainly worth further investigation, as at present there are no pharmacological treatments specifically designed for people living with Down's.
Where did the story come from?
The study was carried out by researchers from the University Pompeu Fabra, Autonomous University of Barcelona, Hospital del Mar Medical Research Institute and CIBER Mental Health, Polytechnic University of Catalonia, University Paris Diderot, University of Paris, Jerome Lejeune, and the Fundacio Catalana Sindrome de Down.
It was funded by the Jerome Lejeune Foundation, Instituto de Salud Carlos III, MINECO and Generalitat de Catalunya.
The study was published in the peer-reviewed journal, The Lancet Neurology.
The reports in the Mail Online, The Telegraph and The Independent take quite a while to mention that most of the test results showed no difference between the groups.
However, they did include quotes from experts making it clear further research and larger trials are needed.
What kind of research was this?
This was a double-blind randomised controlled trial (RCT), which is the best way of telling whether a treatment works.
However, it was relatively small (84 people) and only lasted one year, so larger studies with longer follow-up are needed to see if the results last.
What did the research involve?
People with Down's syndrome aged 16 to 34 were divided randomly into two groups.
Everyone was given online thinking and memory training three times a week for a year. Half the people in the group took capsules of EGCG, while half took placebo.
The participants had tests of their thinking and behavioural abilities at the start, after six months and 12 months, then six months after the study ended. Researchers compared the results between the groups.
The study used tests of thinking and memory developed to test cognitive abilities, including:
- reaction speeds
- ability to make decisions
- use of language
- ability to adapt to different circumstances
- ability to carry out everyday functions and the resulting effects on quality of life
These tests are still under development in relation to their ability to measure changes in ability among people with Down's syndrome.
Researchers compared the results of the tests between the two groups to see whether EGCG had an effect over and above any effects seen from thinking and memory training.
As well as the tests of thinking and behaviour, a sub-group in the study had brain scans using functional MRI – a type of brain scan that can track real-time activity inside the brain – and transcranial magnetic stimulation to measure connectivity patterns between brain cells.
However, these tests were done to explore what might be happening in the brain and were not designed to show a difference between groups.
What were the basic results?
For most of the tests (21 of 24) there were no differences between the groups.
However, in three tests people who'd taken EGCG did better. This improvement lasted for six months after the study ended.
- remembering and recognising patterns
- inhibitory control – the ability to override instinct to follow instructions; for example; in this test, to say "cat" when shown a picture of a dog, and vice versa
- ability to carry out everyday living tasks (adaptive behaviour)
It is not clear how much difference these improvements made to people's everyday lives. We don't know whether the differences in scores between the EGCG and placebo groups were big enough to be noticeable.
People who took the green tea extract did not have an improvement in their overall quality of life, compared with those taking placebo.
How did the researchers interpret the results?
The researchers said that, "Even though the effects of EGCG and cognitive training on cognitive function were small and of subclinical magnitude, they were accompanied by a positive functional change on adaptive behaviour, with an absence of relevant negative side effects."
In other words, they admit most of the tests showed little difference, and those differences they did find might not be important.
But the researchers said the improvement in people's ability to carry out everyday tasks and the apparent lack of side effects means the benefits are "substantial".
They say their exploratory brain scans showed EGCG might affect the brain's ability to make connections between brain cells, and this could be linked to the extract's effect in inhibiting an enzyme called DYRKIA, which is overexpressed in people with Down's syndrome.
This is an interesting, but early-stage, study into a treatment that might help people with Down's syndrome cope better with everyday life.
However, the study does not provide conclusive evidence that green tea extract makes a big difference to people's thinking, memory or behaviour.
Down's syndrome is a complex condition caused by an extra copy of a chromosome in someone's genes. It's not usually inherited. It has a range of effects, which include learning disabilities of differing degrees of seriousness.
While early intensive training in childhood may help, there are no approved treatments for adults to improve learning disabilities.
Research into treatments or training that can help people with Down's syndrome to live a more independent life is very welcome.
This study has a number of limitations. The researchers looked at a wide range of test results, only a few of which were positive.
Carrying out multiple tests increases the risk that some results may be positive simply because of chance.
Also, the tests for changes in cognitive function in this group of people are not yet established, so we can't be sure they are a reliable way of measuring cognitive improvements.
Bigger, longer-running studies might help establish whether green tea extract really is useful alongside cognitive training for people with Down's syndrome.
We also need to see toxicity studies to be sure that high levels of green tea extract are safe for adults and children with this condition.
While a few cups of green tea shouldn't pose any threat to health, there have been warnings that people living with Down's syndrome, or their carers, should not "self-medicate" with green tea extract because of this uncertainty.