A couple of cups of green tea per day reduces the risk of dementia
Drinking green tea every day reduces the risk of cognitive decline and dementia. People who drink green tea on a regular basis, at least 2 cups a day, are roughly 30 percent less likely to develop dementia or other cognitive disorders.
The risk only decreases by six percent if people just drink one cup of green tea a day. Drinking black tea has not been found to have a similar protective effect. Even though green tea has been thought to preserve cognitive abilities for some time, researchers from Tianjin University in China have now reviewed the results of 17 studies that focus on the cognitive abilities of 48,435 people. The tea drinkers show a significant reduction in the risk of cognitive impairment, cognitive decline and dementia.
Although we do not know exactly why green tea has a protective effect, we know that it contains flavonoids. These substances help keep the blood vessels that ‘nourish’ the brain healthy. In addition, green tea also contains caffeine which promotes mental alertness. And finally green tea contains L-theanine, which is thought to have a calming effect. A different study established that black tea (which contains fewer flavonoids) should ideally only be allowed to infuse for two minutes. Those two minutes are enough to release the flavonoids. Infusing the tea for longer than two minutes did not make a significant difference.
Sources: Oncotarget, 2017 ; 8:43306-21 (study focusing on green tea) and JAOAC Int, 2017; 100:1694-9 (study investigating the optimal tea infusion time)
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