People who drink this beverage are less likely to develop dementia.
Are you of the opinion that green tea smells like field of alfalfa and tastes … meh, at best? You are not alone. I thought that, too. But then, as luck would have it, I developed sensitivity to caffeine. It would send my blood pressure through the roof and had my heart racing. That’s how I learned to appreciate green tea. And if you are not a green tea fan, I want to convert you into a believer.
Without a doubt, it is an acquired taste for many of us. It tends to be subtle. You almost have to search for the flavor. It doesn’t help that, what usually passes for green tea in US, could be considered a tea plant floor sweepings.
Meanwhile, hardly a week passes by without some benefits of green tea being touted in press. Within last years several interesting studies came to my attention, linking green tea with benefits on memory and cognition in general. The conclusion of the most recent study by Dr. Tomata was pretty straightforward: “Green tea consumption is significantly associated with a lower risk of incident dementia.”
I once heard a saying: Tea is liquid wisdom. Turns out it is true – quite literally.
I’ve been always a sucker for mixing business with pleasure. Now, that I actually learned to enjoy green tea, I was thrilled to know that at the same time I was feeding my gray matter some good stuff.
So here is what Tomata and his colleagues from Tohoku University did: they followed 13,645 people from Miyagi Prefecture, Japan that were 65 years and older over the course of 6 years. The larger the epidemiological study is, the better the quality, as there is less possibility of results being affected by chance – and 13,000 is a lot of people. Researchers administered memory test at baseline and then at follow up to detect dementia. The group was then analyzed based on their tea consumption (green, oolong and black) as well as the amount of tea they drank. The risk of developing dementia was significantly lower in green tea group. People who drank 3-4 cups were 26% less likely to come down with memory problems. In the group who drank over 5 cups of tea, the risk was reduced by 40%. For black and oolong tea there was some, but much weaker association, which did not reach clinical significance.
Two years earlier, Singapore Longitudinal Aging Study followed a group of 957 elderly men and women over a course of 5 years, testing their memory at baseline and then at follow up. They have also investigated multiple possible factors that could influence memory scores, including self reported physical activity, engaging in social and productive activities, eating fish, fruits and vegetables and drinking tea and coffee. Analysis of data showed significant correlation with only two factors: social engagement (obviously!) and drinking tea.
People who drank moderate amount of green tea were 64% less likely to develop cognitive problems when compared with people who didn’t drink it at all.
Interestingly, in this study, higher amount of tea intake did not necessarily increase the protective effect. People who drank over 5 cups of tea had only 54% risk reduction. The protective effects of green tea were stronger in women and carriers of APOE4 (single most important risk gene for Alzheimer’s disease). Similarly as in Japanese study, black and oolong tea also offered a reduced risk, but to a lesser degree.
This is exciting data. There are other reports, coming from Norway and US showing similar results. We knew before that a cup of tea could clear the mind; it has been used by Chinese as “cognitive enhancer” for centuries. But now, we can see that aside from short term benefits, green tea had long-term benefit.
Scientists are hard at work trying to understand just how does green tea work. A recent study from University of Basel, Switzerland, sheds some light at how it may exert its short-term effects. Twelve healthy vounteers were rounded up and had their brains were scanned using fMRI (functional magnetic resonance imaging, measuring brain activity rather than structure) while having their memory tested. Patients were given soft drink containing green tea extract or a control substance without tea. Brains of people given green tea lit up showing increased activity between the frontal and parietal cortex. More importantly, their memory scores significantly improved.
There is no definitive word on how green tea might affect the long-term cognition. Theories abound. Caffeine, which was considered to be the main component responsible for short-term benefits, has shown some surprising effects in animal studies, for instance reducing the level of beta amyloid (responsible for plaque seen in brains of people with Alzheimer’s disease) in mice. L-theanine, a compound more specific to green tea, increased level of BDNF (brain derived neurotropic factor) and NGF (nerve growth factor) in rats. Both factors are known to increase formation of new neurons and are neuroprotective. L-theanine seems to work as acetylocholine esterase inhibitor (similarly to anti-dementia drugs Aricept and Exelon) and it also helps with relaxation by decreasing caffeine-induced high. And finally EGCG (epigallocatechin 3 gallate), the main catechin in green tea, crosses blood-brain barrier (a smart mechanism that is very selective in what substance it’ll let to get through to our command center) and increases blood circulation . It is also the main antioxidant in green tea, which modulates oxidative stress and inflammation.
While there is always room for more research, for now I would say this: drinking green tea is a simple, cheap and safe intervention for these of us who want to protect their cognition. It is pleasurable, to boot. How many medical interventions that are actually pleasant can you name of the top of your head?
All kinds of tea will give you the benefit. Green, black and oolong teas come from the same plant, Camellia sinensis. They are just processed differently. Green tea, because it contains just dried leaves (as opposed to withered and fermented leaves of oolong and black tea), retains the highest amount of antioxidants and relatively little caffeine.
When you brew your green tea, bear these few things in mind:
- according to a watchdog group ConsumerLab, Chinese green tea may be contaminated with lead and other heavy metals. Being labeled as “organic” may not matter. Tea imported from Japan has been shown to have less contamination.
- you will get most of your beneficial catechins, especially EGCG from powdered matcha tea, as opposed to tea bags. Bottled green tea hardly contains any EGCG at all.
- gyokuro (jade dew) tea, specially grown in shade for last 2 weeks before harvest, seems to have the most EGCG from all green teas. It also has a fuller flavor. Accordingly, expect to pay much more than for regular green tea.to improve taste, follow the suggested water temperature and steeping time. Brewing green tea for too long in water that is too hot will result in greater release of tannins, resulting in bitter-tasting tea. Most green teas require water temperature of 180° F and steeping time of no longer than 3 minutes.
Have you ever wondered why in US we drink relatively little tea as compared with other parts of the world? Like most things that make you scratch your head in wonder, it was politics. Yep, you guessed it: the British Tea Act and Boston Tea Party. Have you known, that after American Revolution drinking tea was considered unpatriotic? It made a powerful statement then, but… it’s been over 230 years since proclamation of Tea Act. Time to get over this particular grudge and our national prejudice against tea and rip its many benefits.
by Anna Lamnari, MD
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