As is known, coffee has stimulating effects that can impair the quality of sleep and fall asleep. Caffeine has a different impact on different individuals. This is due in particular to certain information contained in our genes. Depending on the metabolism to which we belong, it is advisable to drink our last cup of coffee at a very specific time… Explanations.
Coffee punctuates the day of many people. A cup in the morning to give yourself a boost, a shot after the meal to continue the day… However, the exciting effect it produces is known to all. Thus, it is advisable not to drink coffee in the evening for example. Studies refine these claims and help to understand why some people are more affected by the effects of caffeine than others.
According to a report published in June 2018 by the Institute for Scientific Information on Coffee (ISIC), caffeine sensitivity depends in part on a liver enzyme (called CYP1A2) that breaks down the caffeine in the body. This version of the gene varies from person to person. According to this report, the population could therefore be separated into several groups: people with a “slow metabolism”, people with a “fast metabolism”. The fast-metabolism group is able to break down caffeine faster than the other group. Thus, the effects of caffeine last less long.
J.W. Langer, a professor at the clinic at the University of Copenhagen and author of the report, says that fast metabolisms can drink “several cups of coffee a day” because their bodies can quickly remove caffeine from their system. This is not the case for others whose “physiological effects of caffeine last longer and are more pronounced”.
Coffee and sleep
Dr. Reardon explains to Well and Good, that a person with a fast metabolism should take his last cup at most before 5:00 p.m. He says: “Let’s not forget that even a fast metabolism could experience a cumulative effect as a result of other cups of coffee drunk early in the day. This can slow down the rate of caffeine breakdown later.” According to the expert, a slow metabolism should drink its last cup of coffee much earlier, between noon and 2:00 p.m. because “it often takes at least eight hours to metabolize the caffeine contained in a cup of coffee.”
Le Figaro Santé corroborates these remarks by reporting data from a study conducted at Henry Ford Hospital in Detroit.
For four days, twelve people in normal sleep had to abstain from drinking coffee. On the other hand, they had to take a tablet at different times. It contained either 400 mg of caffeine (the equivalent of two to three cups of ground coffee) or an inactive product (a placebo). The volunteers did not know if the tablet taken contained caffeine or not. The first three days, the first tablet had to be ingested six hours before the envisaged bedtime, the second three hours before and the last tablet had to be swallowed at bedtime. On the fourth day, all three tablets were placebos only. Enough to measure the effects of a night spent without caffeine.
The results of the study confirmed the harmful effects of caffeine on sleep when taken too close to bedtime.
« In the experiment, even taken six hours before bedtime, caffeine reduced the usual amount of sleep since the guinea pigs slept on average one hour less than the night following a caffeine-free day. The researchers were able to demonstrate for the first time that late afternoon coffee actually harms sleep. “The second lesson of this study, even more astonishing, is that this loss of an hour of sleep went completely unnoticed by sleepers, who felt like they were doing their usual night.” explains the newspaper.
Finally, experts also warn about hidden sources of caffeine (tea, sodas, energy drinks…).