All those cups of coffee you drink to stay alert could be paying off, according to a new study.
Research published in the journal JAMA Internal Medicine says drinking eight cups of coffee a day - or even more - could lower risk of death over a 10-year period.
Caffeine is metabolised by a liver enzyme coded by the gene CYP1A2. If you carry one or two "bad" copies of this gene, it will slow your ability to process caffeine and you may be more sensitive than someone else, according to Dr Alex Rinehart.
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The new study of half a million people in the UK suggests a lower risk of death was associated with drinking more coffee, including among coffee drinkers who have eight or more cups per day, in both slow and fast metabolisers of caffeine, and in drinkers of ground, instant and decaffeinated coffee.
But the researchers warn people should be cautious about interpreting the results because they are based on observational data and cannot prove cause and effect.
Coffee is popular around the globe and studies have generally reported associations moving in opposite directions between its consumption and the risk of chronic diseases and death. But the study found that even those who carry the "bad" copies of the gene CYP1A2 were at a lower risk of death.
However, caffeine is a strong stimulant, and it can make it harder to get to sleep. According to the University of Otago's Sleep Investigation Centre, it can take anywhere between 15 and 35 hours to eliminate caffeine from your system.
The centre recommends no caffeine within four hours of bedtime, and no more than 300mg a day - that's about three cups.