Or does it? The latest research suggests that familiar buzz doesn't so much as give us a lift, but fights the caffeine withdrawal symptoms - fatigue, mental fogginess and a dull headache - that have kicked in since our last cup.
Indeed, experts suggest that this morning ritual is actually a sign of mass drug dependency.
'People who consume caffeine regularly will become dependent on it - if you take caffeine away from them, they will function below par,' says Peter Rogers, professor of biological psychology at Bristol University and a leading expert on caffeine.
'They just don't function normally without the drug on board. If it's your first tea or coffee of the day, it gets you back to normal, but beyond that you don't get much more of a kick.'
Professor Rogers has studied coffee and its effects for more than 20 years and, as a result, he and other members of his team have given up caffeine.
'On balance, caffeine is not particularly helpful. It triggers withdrawal and increases your blood pressure, which is not a good thing,' he says.
'I sometimes think one of the biggest effects of my research work has been on my department. Four or five colleagues have given up caffeine, and we're all on decaf.'
WHY COFFEE DOESN'T GIVE YOU A BOOST
The idea that caffeine doesn't perk up your brain might sound absurd, but that's what Professor Roger's research shows.
In one key study, around 300 volunteers - half had a moderate to high caffeine intake, the others had a low intake - were asked to stop drinking coffee for 16 hours before undergoing tests.
The volunteers were randomly split into two groups and given a placebo or coffee. The results, in the journal Neuropsychopharmacology, were intriguing.
Though the regular coffee drinkers did have an increase in alertness following the coffee, this only made them as alert as non-coffee drinkers who had the placebo.
In other words, drinking coffee doesn't make us any more alert than non-coffee drinkers.
...BUT WHY YOU THINK IT DOES
Caffeine stops a brain chemical known as adenosine having an effect.
Normally, adenosine helps slow down reactions in the body. As caffeine effectively stops adenosine latching onto cells, it means that when we drink it our body is constantly on the accelerator, not the brake.
Then within a few hours of stopping drinking coffee, the withdrawal effects start to kick in. In some cases, they can even cause flu-like symptoms.
Our body experiences a flood of adenosine, leading to fatigue. Many will also experience a dull headache.
This is because caffeine narrows blood vessels in the brain, says Professor Rogers, so when we stop drinking it, there is an increase in blood flow, which triggers a headache.
'On the rare occasions I have drunk coffee for a few days, when I stop I start to feel under the weather and think I am coming down with a cold,' says Professor Rogers.
'But then I remember - this is what caffeine withdrawal feels like.'
IT WON'T IMPROVE CONCENTRATION
Another recent study by Professor Rogers involving 300 volunteers found coffee doesn't increase alertness, concentration or reaction time, but it will keep you awake.
'I have coffee when I'm driving across Europe, as I know it will keep me awake. But it wouldn't be helpful if I was trying to write a scientific paper late at night as it doesn't help focus or thinking.'
IS CAFFEINE GOOD OR BAD FOR THE HEART?
Aside from triggering a physical dependency, what other effects does caffeine have on our health?
One week we read a report showing caffeine is good for us; the next that it is bad. The experts are fiercely divided.
'It is a well-established and reliable fact that caffeine increases blood pressure,' says caffeine researcher Jack James, professor of psychology at Reykjavik University.
'The increase is modest, but likely to be clinically significant over the course of a lifetime of consuming caffeine.
'I'm confident that in time caffeine consumption will be regarded as a risk to cardiovascular health.'
One paper by Professor James, who is also editor of the Journal of Caffeine Research, suggests regular caffeine may account for 14 per cent of premature deaths due to coronary heart disease and 20 per cent of premature deaths due to stroke.
And in a study published just a few weeks ago, Australian researchers suggested a chemical in coffee called chlorogenic acid may increase the risk of diabetes and even lead to the body storing excess fat.
The study, published in the Journal of Agriculture and Food Chemistry, showed that when mice were given high amounts of this compound, the equivalent of drinking five or six cups a day, their bodies struggled to control blood sugar and they developed insulin resistance. They were also less likely to lose weight.
However, other research has shown that regular coffee and tea intake reduces the risk of stroke and heart disease, as well as neurodegenerative diseases such as Parkinson's.
Indeed, one large study undertaken by Harvard researchers, and published last year in the journal Circulation, suggested that moderate coffee intake (four cups a day) reduced the risk of heart failure.
The team looked at research from five studies, involving more than 140,000 people.
'There is a growing body of research suggesting coffee is beneficial and this paper added to this,' says Dr Elizabeth Mostofsky, a post-doctoral research fellow and lead researcher of the paper.
Coffee consumption has also been linked to a lower risk of type 2 diabetes and some forms of cancer.
However, as with everything, moderation is best. Drinking more than ten cups a day 'may be harmful', says Dr Mostofsky.
She suggests that patients who are at risk of stroke and not regular coffee drinkers may want to consider avoiding it. Some of her earlier research suggests the peak in blood pressure immediately after having coffee may briefly increase stroke risk (the effect was not seen for tea).
But, overall, Dr Mostofsky believes the effects are positive. 'It's nice to know there may be health benefits from the number one drug consumed,' she says.
SHOULD YOU SWITCH TO DECAF?
So what are we to make of this wealth of apparently conflicting evidence?
Professor Rogers suggests that, in fact, the benefits of coffee and tea lie in the antioxidants that they contain - compounds that work to lower inflammation in the body.
Inflammation has been linked to a host of diseases such as stroke, cardiovascular disease and cancer, and so antioxidants consumed in tea and coffee may reduce the risk of these diseases.
This is why he still drinks decaffeinated tea and coffee (five cups of tea and one cup of coffee a day).
But he says the effect would not be seen with caffeine-filled energy drinks.
'Compounds in tea and coffee may be producing beneficial effects, but in other drinks, such as energy drinks, there aren't these naturally occurring compounds to balance out the effect of caffeine.'
And he believes that the rise in caffeine products will only fuel our dependency.
