Tea may lower anxiety and blood pressure AFP Relax – Fri, Nov 2, 2012

A new study supports prior evidence that tea can not only reduce blood pressure but calm anxiety, despite its caffeine content.
Japanese researchers tested two compounds found in tea — L-theanine, the amino acid contained in tea leaves, and caffeine — and their effect in the body when under stress. They enlisted 14 subjects who underwent three separate trials, in which they took L-theanine and a placebo, caffeine and a placebo, or a placebo only. The subjects were then asked to complete mental activities under varying degrees of stress, such as solving arithmetic questions with their non-dominant hand submerged in a bucket of ice water.

Ai Yoto and her team from the University of Shizuoka found that L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of subjects whose blood pressure rose more than average while performing a mental task after taking a placebo. Caffeine also had an effect on blood pressure, but to a lesser degree than L-theanine. In addition, the L-theanine was shown to reduce tension-anxiety scores on mood tests.

The study was published this week in the Journal of Physiological Anthropology.


Caffeine is the most commonly consumed psychoactive substance worldwide and an active ingredient in innumerable beverages and foods.
Its neurobiological effects comprise mainly stimulatory actions on alertness, attention, cognitive performance, and blood flow to the brain.
It is known to reduce sleepiness, to prolong sleep latency, and to enhance wake periods after sleep onset
Read more: http://www.dailymail.co.uk/sciencetech/article-2226768/Brain-scans-reveal-effect-coffee-brain-offer-tantalising-clues-help-ward-dementia.html#ixzz2BGJ7zxTO
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The scans that show how caffeine takes over your brain and stops you getting tired
Caffeine is the world’s most popular psychoactive drug and found in a range of foods and drinks
Previous studies have shown coffee regular drinkers are less likely to develop dementia in later life
PUBLISHED: 09:46 GMT, 2 November 2012 | UPDATED: 16:30 GMT, 2 November 2012


Brain scans have for the first time revealed the effects of caffeine on the living human brain and have offered clues as to coffee drinks are at a lower risk of developing of dementia.
Caffeine is the world’s most commonly consumed psychoactive drug and an active ingredient in a range of different foods and drinks.
In the U.S., 80 per cent of adults taking caffeine everyday – each consuming an average of 200mg, equivalent to two 5oz cups or four cans of Coca-Cola

‘There is substantial evidence that caffeine is protective against neurodegenerative diseases like Parkinson’s or Alzheimer’s disease,’ said Dr David Elmenhorst, of the the Institute of Neuroscience and Medicine.
‘Several investigations show that moderate coffee consumption of 3 to 5 cups per day at mid-life is linked to a reduced risk of dementia in late life.’

To investigate why, Dr Elmenhorst and his team used molecular imaging with positron emission tomography to investigate the effects of caffeine on the brains of 15 male volunteers aged between 24 and 66.
The volunteers were asked to abstain from any caffeine intake for 36 hours, before an initial PET scan to determine their brains’ baseline state.

Researchers then injected caffeine directly into the subjects in increasing amounts, scanning their brains as they went along.
The team found that the repeated intake of caffeine can occupy up to 50 per cent of the brain’s A1 adenosine receptors, stopping these from receiving the sleep-promoting neurotransmitter they were intended to absorb.
It is likely that this blockage of a substantial amount of cerebral A1 adenosine receptors will result in adaptive changes and lead to chronic alterations of receptor express and availability, they said.
They determined that it was this structure that may offer some insight as to why coffee drinkers were at lesser risk of dementia.
‘The present study provides evidence that typical caffeine doses result in a high A1 adenosine receptor occupancy and supports the view that the A1 adenosine receptor deserves broader attention in the context of neurodegenerative disorders,’ said Dr Elmenhorst, lead author of the study published in The Journal of Nuclear Medicine.
Read more: http://www.dailymail.co.uk/sciencetech/article-2226768/Brain-scans-reveal-effect-coffee-brain-offer-tantalising-clues-help-ward-dementia.html#ixzz2BGJ2EN8X
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