HOW LONG DOES IT TAKE?

. . . for the effects of coffee to wear off: up to 12 hours

‘WHEN you drink a cup of coffee, it will take about 45 minutes for the caffeine to enter your system via the membranes of the mouth, throat and stomach,’ explains dietitian Sarah Schenker. ‘This activates brain cells that release the chemical noradrenaline and stimulates dopamine, which raise energy.

‘The caffeine in two cups of coffee will still have effects in the average person’s system around six hours later and be fully eliminated around 12 hours later.’

However, the speed of metabolism can be affected by an enzyme called cytochrome P450 1A2. Some people have a more efficient version of this, so caffeine clears rapidly.

Female hormones can also have an effect. A study at Vanderbilt University in the U.S. found it took 10.7 hours for the amount of caffeine in the blood to reduce by half in women on the Pill, but just 6.2 hours for other women.