Doesn’t energize, but causes drowsiness: why coffee acts this way.
Coffee is traditionally considered a powerful stimulant, whose main goal is to provide energy and improve concentration. However, many people unexpectedly encounter the opposite effect: strong drowsiness, heaviness in the eyelids, and a feeling of fatigue arise 30–60 minutes after a cup. This paradoxical effect is not an individual anomaly, but a physiologically conditioned phenomenon related to how caffeine interacts with the brain and the body as a whole.
Why the effect of coffee suddenly stops: it’s about adenosine
Adenosine — a neurotransmitter that gradually accumulates in the brain throughout the day and signals the need for rest — plays a key role in the feeling of fatigue. The action of caffeine lies in the fact that it is an antagonist of adenosine — caffeine has a similar chemical structure and physically blocks the receptors to which adenosine should bind.
As long as these receptors are blocked, the feeling of fatigue is suppressed, and a person experiences a surge of energy. However, it is important to remember that adenosine continues to be produced even when its receptors are blocked. Once the effect of caffeine wears off, the accumulated supply of this substance simultaneously "comes out" with double force, binding to the receptors.
This massive "influx" of adenosine leads to a sudden and strong feeling of fatigue, known as a "coffee crash." This effect is intensified if the coffee was consumed on an empty stomach or in a state of chronic fatigue, when the body has already exhausted its reserves.
Disruption of sleep quality
Although many people drink coffee only during the day, caffeine can disrupt sleep quality even if consumed several hours before bedtime. Coffee reduces the depth of slow-wave sleep, which is critically important for the recovery of the body and the nervous system. As a result, despite coffee consumption, the brain continues to experience a deficit of renewal, and drowsiness manifests during the day as a natural response to a lack of proper rest.
Dehydration and lethargy
Caffeine has a mild diuretic effect. Without sufficient intake of pure water, the body may face mild dehydration (fluid deficiency). This reduces the efficiency of blood circulation, decreases oxygen delivery to cells, and causes feelings of lethargy, heaviness in the head, and drowsiness. These symptoms are often mistakenly attributed to "lack of caffeine," when in fact they are signs of disrupted water balance.
Hormonal rollback and sugar imbalance
Firstly, for some people, caffeine provokes a sharp release of adrenaline and cortisol — stress hormones that temporarily increase alertness. However, after the peak action of these hormones, there is a rapid rollback, and the nervous system enters a state of exhaustion, perceived as sudden fatigue or "shutdown."
Secondly, if coffee is consumed with added sugar, syrups, or sweet cream, the rapid influx of sugar causes a sharp spike in glucose levels. In response, the pancreas actively produces insulin, and its excess can lead to a rapid drop in sugar levels or hypoglycemia, which manifests as weakness, drowsiness, and lethargy.
Individual metabolic features
The reaction to caffeine is also individual and depends on genetic characteristics. The speed at which the body breaks down caffeine is determined by the activity of liver enzymes. For people who metabolize caffeine very quickly, the stimulating effect will be short-lived, and it will be quickly followed by a sharp "crash" of fatigue.
How to avoid the opposite effect of drowsiness after coffee
To minimize paradoxical drowsiness after coffee, several rules should be followed.
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Firstly, it is not recommended to consume coffee on an empty stomach; it is better to drink it with light food containing proteins or complex carbohydrates that slow the absorption of caffeine and soften its sharp fluctuations.
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Secondly, always drink water alongside coffee to maintain water balance and compensate for the diuretic effect of caffeine.
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Thirdly, it is better to divide the daily portion into two or three small doses rather than drinking a large cup at once to avoid a sharp "crash."
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Fourthly, it is important to remember that coffee does not replace proper sleep; it only temporarily masks its deficit. If you feel sleepy after a cup of coffee, it means that your body needs rest, not additional stimulation.
