Coffee does NOT wake you up. It's all in your mind

Drinking coffee can make you feel alert because it reverses the effect of caffeine withdrawal according to a new study

Many people depend on a morning cup of coffee as a wake-up call for the brain.
But the effect could be all in the mind, according to new research.
Tests show the mental stimulation for which caffeine is famous may be nothing more than an illusion - with the body simply compensating for overnight withdrawal symptoms.
A new study suggests coffee drinkers may actually be better off without their habitual morning mug as it raises the risk of anxiety and high blood pressure.
Altogether 379 people who abstained from caffeine for 16 hours before drinking either caffeine or a placebo (dummy drink) were tested for a range of responses afterwards.
Bristol University researchers found little variance in levels of alertness among the volunteers.
The findings suggest frequent coffee drinkers develop a tolerance to both the anxiety-producing effects and the stimulatory effects of caffeine. 
While frequent consumers may feel alerted by coffee, this is probably the reversal of the fatiguing effects of acute caffeine withdrawal, claim researchers. 
As caffeine can make consumers prone to anxiety and raised blood pressure, there is no net benefit to be gained, says a report published online in the journal of Neuropsychopharmacology.
Peter Rogers, from the University of Bristol's Department of Experimental Psychology and one of the lead authors of the study, said 'Our study shows that we don't gain an advantage from consuming caffeine - although we feel alerted by it, this is caffeine just bringing us back to normal.
'On the other hand, while caffeine can increase anxiety, tolerance means that for most caffeine consumers this effect is negligible.'
Around half of volunteers drank little or no caffeine and the other half were medium-high caffeine consumers.
All were asked to rate their personal levels of anxiety, alertness and headache before and after being given either the caffeine or the placebo. 
They were also asked to carry out a series of computer tasks to test for their levels of memory, attentiveness and vigilance.
The medium-high caffeine consumers who received the dummy drink reported a fall in alertness and an increase in headache, neither of which were reported by those who received caffeine.
However, their post-caffeine levels of alertness were no higher than those drinking low levels of caffeine who received a placebo, suggesting caffeine only brings coffee drinkers back up to 'normal'.
The authors also found a genetic predisposition to anxiety did not deter coffee drinking.
In fact, people with the gene variant associated with anxiety tended to consume slightly larger amounts of coffee than those without the variant, suggesting a mild increase in anxiety may be a part of the pleasant buzz caused by caffeine.
A single cup of instant coffee contains 60-100mg of caffeine depending on the strength of the brew; a cup of tea contains 30-100mg of caffeine; and a latte or espresso contains 90-200mg of caffeine. A 55g chocolate bar contains 40-50mg of caffeine.
Dr Sarah Schenker, Independent Dietitian, said 'There is growing evidence to show that individuals do respond to caffeine differently depending on their tolerance levels.
'Studies have shown that when single large doses of caffeine are consumed, around 300mg or more in one go, then there is an effect of increased anxiety.
'However, many people are used to the positive effect of increasing alertness that they gain from a lower dose of 100mg - equivalent to an average mug of coffee.'
Dr Euan Paul, Executive Director of the British Coffee Association, said 'There is an overwhelming wealth of evidence showing that caffeine does increase alertness levels by acting as a stimulant on the central nervous system by prompting the release of adrenaline.
'This effect is not only found with subjects in a low state of alertness such as night time shift workers, or those who wake-up early in the morning, but is additionally found in subjects who already have a high state of alertness.
'Further research is required to look at how the results of this new study may affect the wider population.
'Coffee when consumed in moderation, 4 – 5 cups per day, is safe and may confer certain health benefits, including contributing to your daily fluid intake.
'Pregnant women should be mindful of the advice given by the Food Standards Agency and limit caffeine intake to 200mg per day from all sources.'