The body needs time to eliminate the effects of caffeine, meaning that a cup of coffee consumed in the afternoon may still affect sleep at night, even if the person does not notice the effect directly.
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An Australian study found that consuming coffee less than 8.8 hours before bedtime may affect sleep quality. This means that someone who goes to bed at 10 p.m. should ideally have their last cup of coffee at around 1 p.m.
The study, published in the journal Sleep Medicine Reviews, reviewed and analyzed the findings of 24 studies examining the effects of caffeine on sleep.
According to the findings, consuming a cup of coffee containing about 107 milligrams of caffeine less than 8.8 hours before bedtime may reduce sleep duration and affect sleep quality. For example, if bedtime is 9 p.m., the last cup of coffee should preferably be consumed around noon. If bedtime is 11 p.m., coffee can be consumed until around 2 p.m.
Energy drinks require more time
People who consume caffeine-containing supplements or drinks before exercising should stop taking them earlier because of their higher caffeine content. Researchers found that a serving of pre-workout drinks contains roughly the equivalent of two cups of coffee and should be consumed at least 13.2 hours before bedtime. Therefore, if bedtime is 11 p.m., it is best to avoid consuming a pre-workout drink after 9:30 a.m.
Caffeine works by blocking the effects of adenosine, a substance that accumulates in the body throughout the day and increases feelings of drowsiness as bedtime approaches.
When caffeine blocks its effects, the body remains alert for longer. The study found that consuming caffeine late in the day may reduce total sleep duration by about 45 minutes, lower sleep efficiency by around 7%, and increase the time needed to fall asleep by about nine minutes.
Caffeine was also associated with reduced deep sleep, with participants in the study losing about 11.7 minutes of this important stage, which is essential for restoring energy and supporting bodily functions.
Regarding the appropriate amount of caffeine, the US Food and Drug Administration (FDA) recommends that adults consume no more than 400 milligrams of caffeine per day. A cup of coffee typically contains 80–100 milligrams of caffeine, while tea contains about 15–70 milligrams. Energy drinks contain between 80 and 300 milligrams.
If caffeine is affecting sleep, reducing the amount consumed or having the last cup earlier in the day may be a simple step toward improving sleep quality. Green tea can also be used as an alternative to coffee, as it contains less caffeine as well as L-theanine, a compound that may promote a sense of calm while maintaining focus.
Daily Mail
