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A Snapshot of Caffeine's Fascinating Effects On The Brain

Wednesday November 07, 2012

Alice G. Walton

forbes.com - Despite caffeine’s shaky reputation in the past, there’s more and more convincing evidence that it’s not only not so bad for us, but in some ways, may actually be quite good for us. It’s the most popular neurostimulant in the world (of the legal ones, anyway), according the authors of a new study that uses brain imaging to look at how caffeine exerts its wondrous effects on the brain. And that description isn’t total hyperbole – previous research has shown caffeine to reduce the risk of neurodegenerative diseases like Alzheimer’s and Parkinson’s. The new study gives us some of the first clues in humans as to why this may be.

The researchers had 15 male participants abstain from drinking or eating anything caffeinated for 36 hours. If these 36 hours were painful for the participants, they at least got rewarded in the lab with an IV drip of caffeine. At the same time, their brains were scanned with positron emission technology (PET), using a radioactive compound that allowed the researchers to visualize where caffeine was going once it arrived in the brain.

Adenosine receptors are found throughout the brain and body. In the brain, adenosine builds up throughout the day, ultimately making us feel tired by the end of it. But caffeine is a brilliant adenosine mimic – so, taking the place of adenosine, it blocks those receptors and keeps us feeling chipper and alert.

It turned out that in regular coffee drinkers, a good number of these adenosine receptors were blocked by caffeine when the people were infused with it. The researchers calculated that it takes about 4-5 cups of coffee to block half of the brain’s adenosine receptors. And they suggest that the cognition-enhancing effects of caffeine are due to this very blockage of the adenosine receptor.

But what’s most interesting about this study is the implications it has for our understanding of certain brain diseases – and the idea that caffeine may reduce our risk for them, which has been suggested before. The authors say that effects of caffeine can build up over time and lead to measurable changes in the brain: If you’re blocking adenosine receptors with caffeine over the long term, this can result in “adaptive changes and lead to chronic alterations of receptor expression and availability,” the authors write. Previous research has hinted at a reduced risk of dementia in regular coffee drinkers, although the exact reasons behind this have not been clear. And in a very recent study in mice, caffeine reduced the kind of inflammation that’s linked to mild cognitive impairment, and it appears to do this through its effect on adenosine levels.

“There is substantial evidence that caffeine is protective against neurodegenerative diseases like Parkinson’s or Alzheimer’s disease,” said author David Elmenhorst. “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.” And this study is exciting in that it may point to an actual mechanism for the connection in humans – although there are certainly likely to be multiple mechanisms involved.

In very high doses, of course, caffeine is not so good for you, and, in the form of energy drinks, has recently been the subject of some serious concern. But if you’re in the “moderate” use group, you may be OK to continue your habit, if you’re not experiencing any unwanted side effects. In fact, it may be a very smart move for your brain.