For years we have been told to beware of caffeine.
Now we seem to have swung in the opposite direction, with studies claiming that moderate amounts of coffee may reduce headaches and protect against diabetes, Alzheimer's and heart disease, among others. So where does the truth lie?
We don't all have the same reactions to caffeine, Mehul Dhinoja, a consultant cardiologist says: “Each of us has an enzyme in the liver that breaks down and metabolises caffeine. It's that process that enables caffeine to have its effect around the body,” he says. “Some people are born with an enzyme that works extremely efficiently and others have quite the opposite.”
Peter Rogers, head of experimental psychology, says some people are more sensitive to the effects of caffeine, while others develop a tolerance. “One of the things caffeine has been found to do is increase blood pressure and make your hands shake a little,” he says. “But actually this depends if you're a person who regularly consumes caffeine.”
You can even develop a dependence on caffeine so that without it, you can feel fatigued and headachey, he says. Caffeine may even have radically different effects on the sexes. Studies from Bristol University have found that drinking caffeinated coffee boosted a woman's performance in stressful situations, but had the opposite effect on men, who became less confident and took longer to complete tasks once they had several coffees.
What caffeine is good for
Forget hair of the dog. If you want to cure a hangover, a good old cup of coffee and aspirin really is best, according to a new study from Thomas Jefferson University in Philadelphia.
Confirming what many have suspected for years, the research found that the caffeine in coffee and the anti-inflammatory ingredients of aspirin reacted against the chemical compounds of ethanol, or pure alcohol, which — even in small doses — can bring on headaches.
Drinking lots of coffee can also boost sports performance by as much as 6pc — but, critically, only in any activity where muscles are not being worked to the limit, meaning coffee or tea could benefit a longdistance runner but not a sprinter.
What it is bad for?
Contrary to popular opinion, one thing coffee doesn't do is sober you up — it may even further impair your judgement, scientists at Temple University in Philadelphia have found.
Combining alcohol and caffeine at the same time produces a potentially lethal mix that makes it harder to realise you are drunk, according to the study published in Behavioural Neuroscience.
Large amounts of caffeine in pregnancy also appear to be risky. The Food Standards Agency has warned women to have no more than two cups of coffee a day after a study linked caffeine to low birth weight.
Caffeine may affect your chances of getting pregnant in the first place. One study found that women who drank four cups of coffee a day were 26pc less likely than average to have conceived naturally.
Cancer and heart disease
Analysis published on the BioMed Central Cancer website suggests that coffee consumption may cut your risk of getting cancer.
However, women who drink more than four cups of coffee a day increase their risk of developing breast cancer by a third, according to Harvard University.
Australian scientists found that drinking three to four cups of coffee a day can lower the risk of Type 2 diabetes by 25pc, but those who drank decaffeinated coffee showed similar results.
Should we give it up?
Doctors often tell patients to quit caffeine, but that may not be necessary, Rogers says.
He followed a group of people with tinnitus — a condition for which caffeine has traditionally been deemed by doctors as a big no-no.
“We found that those who did give up caffeine didn't improve their condition in any way.
“Not to undermine the importance of my own research, but tea and coffee are things to worry about so much less than if you're a smoker, overweight or have a poor diet.”