Why Coffee Makes You Sleepy: Five Science-Proven Reasons

Caffeine – is the most widely used stimulant in the world. But it doesn’t work for everyone the same. Some people can drink several cups of coffee daily and get little benefit from it. However, some are drawn to taking a nap after drinking a cup. We discovered why this happens and how to drink coffee, so it invigorates, not lulls. Read about five possible causes of sleepiness.

Reason One. Coffee relieves fatigue only for a while

It works through unique molecular mechanisms – a blockage of adenosine receptors in the brain. Adenosine is responsible for the sleep-wake cycle. Its amount increases during the day and decreases during sleep.

Adenosine molecules bind to special receptors to prepare the brain for sleep, and brain activity begins to slow down. Caffeine blocks this connection by binding to adenosine receptors.

Caffeine is absorbed very quickly; the first effects can be felt after a few minutes, and within 45 minutes absorbs 99% of the caffeine.

After the effect of caffeine wears off, adenosine can reattach to its receptors – and this causes a feeling of drowsiness.


Reason Two. The body loses more fluid.

Coffee speeds up metabolism, so it can be helpful for those who like to spend time in the gym. However, the drink has a slight diuretic effect. Therefore, if after a couple of cups you go in for sports, you may lose more fluid than usual. Because of its lack, people often feel lethargic, tired and sleepy.

How to avoid dehydration

Drink water throughout the day, and eat more fruits and vegetables.

Reason Three. Poor coffee quality

A strange smell and too strong bitterness are characteristic signs of low-quality coffee. It may contain toxins that mould releases. Many studies have confirmed that this can cause fatigue and dizziness.

How to avoid intoxication

Do not drink coffee of dubious quality. Choose coffee from trusted brands, and do not store an expired product.


Reason Four. Too much sugar

Sugar is absorbed by the body faster than caffeine. Some people have a sharp drop in glucose levels as early as an hour and a half after drinking sweet coffee. This may result in fatigue.

How to Avoid Sugar Fatigue

Avoid sweeteners. The WHO advises limiting sugar intake to 10% of the daily calories required to maintain health.


Reason Five. Caffeine can cause anxiety.

Many studies confirm that caffeine produces stress hormones – adrenaline and cortisol. If you sleep less than seven hours a night, week after week, after a few cups of espresso, your heart rate and anxiety may increase, causing overwork and drowsiness.


How to avoid anxiety

A good night’s sleep will reduce anxiety and help you think clearly. If you do not neglect rest and do not abuse coffee, then you will definitely benefit from the drink. It has been proven that caffeine reduces inflammation, strengthens the heart and blood vessels, reduces the risk of developing diabetes, and can even delay ageing.

How to drink coffee correctly so that it benefits

  1. Approach your coffee intake strategically. If you have an important meeting where you need to be as focused as possible in half an hour, then it’s time to drink a cup.
  2. Keep track of your condition. If you feel restless, dizzy, or have heart palpitations after coffee, limit its use or refuse it for a while.
  3. Drink clean water with your coffee, either at the same time or after your coffee break. Supporters of the first method believe that a sip of water refreshes the receptors after a sip of coffee. Adherents of the second method are sure that in this way, you will protect yourself from mild dehydration and stay cheerful longer!
  4. Drink coffee when cortisol levels are low. This will make the drink work better. If you get up at 7:00, the best period for you is between 9:30 and 11:30. If later, add 2-3 hours to the time of awakening. But immediately after you wake up, it is better to drink water with lemon.


How to Avoid Drowsiness

Drink grapefruit juice with coffee: thanks to grapefruit enzymes, caffeine lasts longer. If that doesn’t help, you’ve developed a tolerance to caffeine. In this case, you must give up your favourite drink, at least for a while.

Scientists say that you should not consume more than 400 mg of caffeine during the day – that’s 3-5 cups. Moreover, it is better to drink the first portion, not in the morning but 2-3 hours after waking up.


Other effects of caffeine

According to a 2016 meta-analysis (review of a large number of studies), caffeine increases blood sugar levels by decreasing insulin sensitivity. People with elevated blood glucose levels can cause headaches, fatigue, trouble concentrating, extreme thirst, and frequent urination until blood sugar levels return to normal.

There is much other evidence that coffee contributes to the development of insomnia. Many researchers are recommended to refrain from this drink at least 6 hours before bedtime.

High doses of caffeine (greater than 400 mg) may cause significant nervousness and anxiety and exacerbate the course of depression.

Some studies suggest that drinking 1-3 cups of coffee daily can reduce the risk of cardiovascular disease. On the other hand, drinking more than 6 cups of coffee daily contributes to increasing this risk. In some works, coffee has even been suggested to have an anti-cancer effect in the context of hepatocellular carcinoma (a type of liver cancer).


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