So-called "energy” drinks have given caffeine a bad name.

Some people, especially teens and young adults, guzzle the stuff.
And some energy-drink fans get heart palpitations and break out in a sweat.
No surprise there. As they say, "duh”!
Other people are kept awake by even small amounts of coffee, tea, or caffeinated soda.
Caffeine's effects are generally benign-to-beneficial, and problems with it usually relate to overuse or an innate hypersensitivity.
For example, see Caffeine May Curb Diabetes.
Routine, moderate caffeine consumption may also help delay age-related cognitive decline and alleviate certain effects of Parkinson's disease and various forms of dementia including Alzheimer's disease.
For more about the encouraging evidence on that front, see Caffeine May Boost Brain Power and Deflect Dementia.
Why do many stressed out people find caffeine calming?
We humans seem to instinctively self-medicate to reduce the effects of stress.
But all too often, we choose alcohol or other damaging drugs. 
Epidemiological studies show that people exposed to repeated stress raise their caffeine intake.
And relatively high caffeine intake has been linked to a reduced risk for depression or suicide (Lara DR 2010; Omagari K et al. 2014; Lucas M et al. 2014)
For example, Harvard Medical School researchers found that among more than 50,000 female nurses, those who reported drinking two or more cups of coffee a day were less likely to get depressed (Lucas M et al. 2011).
Decaffeinated coffee did not have the same effect.
However, the reason for the apparent protective effects of caffeine against depression has been unclear.
Strong evidence suggests that caffeine alleviates chronic stress in part by increasing brain levels of the neurotransmitter dopamine.
This may explain why caffeine can alleviate some symptoms of Parkinson's disease, which are caused by deficiencies in dopamine production.
Recently, researchers tested the effects of caffeine in mice exposed to chronic, unpredictable stress.
Their findings lend support to the idea that caffeine can ease stress, and they further illuminate the role of neurotransmitters in stress.
Mouse study links caffeine to reduced stress, and reveals why
The new experiment comes from scientists at Boston University and colleagues from Portugal, Germany, and Brazil (Kaster MP et al. 2015).
They found that caffeine helped the animals remain relaxed in stressful situations … and their experiment also pinpointed the neurochemical pathways involved in caffeine's beneficial effects on stress.
Caffeine tends to block brain-cell receptors for the neurotransmitter called adenosine.
The role of adenosine varies, depending on what brain cell receptor it hits, and the locations of those receptors.
Adenosine 2A receptors in the hippocampus – the brain's memory center – seem to be related to stress as well as to Alzheimer's disease.
The researchers behind the new study found that adenosine 2A receptors in the hippocampus help regulate the negative effects of chronic stress … and that stress-induced behavior can be reversed by blocking the receptors.
And this landmark study is the first to reveal how – by blocking adenosine 2A receptors – caffeine may prevent some of the negative effects of chronic stress.
The international team suggest that their findings may lead to medical therapies for stress-related illnesses.
Of course, stress is a normal human reaction to events, and the last thing we need is another psychiatric drug that ignores the root of the problem.
But it's often difficult to remove the source of the stress.
In such cases, it makes sense to reduce the tendency for chronic stress to trigger damaging and counterproductive physiological and psychological responses.
In other words, the take away from this preliminary study may be that people under stress should try drinking coffee or tea … not wine, beer, or cocktails.
Can curcumin help too?
The bright-orange antioxidant pigment in turmeric – called curcumin – may also be a key ally against the effects of chronic stress.
A remarkable series of studies by scientists at Peking University and the University of Florida found that supplemental curcumin actually reversed the learning and memory disturbances produced by chronic stress (Xu Y et al. 2006; Xu Y et al. 2007; Xu Y et al. 2009; Xu Y et al. 2011).
Unlike caffeine however, curcumin appears to reduce brain damage caused by the stress hormone cortisol.
And like omega-3 fatty acids, curcumin's anti-stress benefits come in part from its ability to raise brain levels of a chemical called BDNF, which increases "neuro-plasticity” … a very good thing.
So it may be a good idea to enjoy plenty of curry, tea, and coffee!
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