A recent study has found that even those who do not typically drink coffee may feel happier throughout the day by starting off with a cup in the morning. However, the study also suggests that drinking coffee later in the day or relying too much on it can have the opposite effect.
This latest study involved researchers from the University of Warwick in the UK and the University of Bielefeld in Germany, with their findings published in a recent issue of the journal “Scientific Reports”.
The study tracked 200 young individuals over a four-week period, measuring their emotional responses. As part of the research, participants received prompts on their phones seven times a day and were asked to record their feelings at the time and the timing of their recent caffeine intake.
Among those who consumed caffeine, the study found that individuals who had a cup of coffee or tea within the first two and a half hours after waking up were in a better mood compared to those who drank coffee later in the day. Researchers noted a positive correlation between the intake of caffeine and an increase in positive emotions such as enthusiasm and happiness.
Psychology professor Anu Realo from the University of Warwick explained that caffeine, by blocking adenosine receptors in the brain, produces positive effects. She stated, “This can increase dopamine activity in key brain areas – research indicates that this effect is related to improving mood and enhancing alertness.”
An earlier study suggested that adenosine makes individuals feel drowsy and caffeine primarily works to counteract the effects of adenosine in the body.
Adenosine levels in the brain are lower upon waking up in the morning and gradually accumulate throughout the day. As more adenosine binds with receptors in the brain, signals for rest are sent, leading to feelings of fatigue and sleepiness.
The energy and alertness brought by coffee primarily rely on the caffeine content. It has been pointed out that caffeine essentially “borrows” energy from the body since the energy boost it provides is essentially a reduction in fatigue signals and does not enhance physical performance or provide energy like food does. A cup of black coffee contains less than 5 calories, thus this energy is essentially “borrowed” from the body.
Adenosine is cleared during sleep, which explains the refreshed feeling upon waking up. Conversely, lack of sleep increases adenosine and adenosine receptors in the brain, causing grogginess, particularly when one hasn’t had a restful night.
A comprehensive analysis published in 2020 showed that through immediate caffeine intake, sleep-deprived individuals can improve cognition, work performance, and driving abilities to some extent. Excessive caffeine intake can impact the body’s resource allocation.
Caffeine directs energy towards enhancing alertness rather than long-term restoration, which may impair muscle recovery, immunity, and sustained energy replenishment during endurance activities. Particularly, drinking coffee later in the day can lower sleep quality, affect cellular repair, and consequently increase long-term health risks.
It is worth mentioning that aside from coffee beans, over 60 plant species worldwide contain caffeine, including tea leaves, guarana berries, and cocoa beans.