Coffee: How does caffeine wake you up?

Are you one of the one billion people who drink coffee daily worldwide? Well, you probably experienced the wonders of coffee and one of these is keeping you up! Whether you need a kick in the morning, grab a drink on the go or plan an all-nighter to finish some work –coffee is always an excellent idea at any time of the day. 

All thanks to caffeine, we have that boost we need every day. A regular cup of coffee typically has around 95 mg of caffeine, which is enough to help you stay awake for several hours [1].

But, to begin with, how does caffeine actually work? 

What is caffeine?

Before we understand how caffeine works, you first need to be familiarised with it. Caffeine is a natural psychoactive substance and is found in plants, including coffee beans, cacao pods, kola nuts and tea leaves. 

To put it simply, caffeine is that bitter taste in your coffee. You can find caffeine in foods and common drinks around the world, especially in coffee, as it is the most potent caffeinated beverage. Caffeine can also be found in tea, soda, energy drinks, and cocoa or chocolate beverages. These drinks are rich sources of antioxidants and phytonutrients, which are technically good for your health.

Aside from these, caffeine can also be included in some minor prescription and non-prescription drugs like cold and allergy medications and pain relievers [2]. One of caffeine’s health benefits is reducing the risk of developing neurological disorders, especially Parkinson’s and dementia. 

How does caffeine work?

Caffeine has similarities to a chemical in your body called adenosine that slows down the rate at which your nerves fire. This sleep-promoting chemical can build up in the brain as you stay awake for a long time, and when this happens, as you might expect, you become sleepier. Caffeine interferes with this chemical’s slowing effect on your brain; hence, your neurons remain active and vigilant instead of winding down. 

As a result, caffeine can make you alert and energised, and for some of us, it helps us concentrate. However, there are times, usually for those with low caffeine intolerance, when the effects of caffeine are negative, like anxiety, restlessness, insomnia and increased heart rate. 

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Caffeine is a stimulant that affects your central nervous system, and the effects can be felt as early as just 15 minutes after you enjoy your cup of joe. Caffeine can peak in the blood for up to 2 hours and remain there for 9 hours as your liver breaks it down [3].

However, there are several factors to consider when determining its time effect on a person. If you are smoking or have caffeine tolerance, the stimulant effects could be reduced, and the breakdown of caffeine can be faster. On the other hand, the caffeine effects can be the opposite for people taking oral contraceptives or who are pregnant.

Types of coffee and caffeine content 

As mentioned, caffeine can be found in various sources, but the most popular one is coffee. For an 8-ounce cup of coffee, there are 80-100 milligrams of caffeine. And, of course, it varies depending on the type of coffee you are drinking [4].

  • Brewed coffee – for this type of coffee, there is around 70-140 mg of caffeine in every 8-ounce cup. The coffee beans are brewed in hot water and usually sit in a paper, metal, or plastic filter. 
  • Cold brew coffee – a 12-ounce cup of this coffee has 153-238 mg of caffeine. The difference with brewed coffee is that it is made without heat. 
  • Decaffeinated brewed – the myth of this coffee is that most of us think it has no caffeine–that’s wrong. Decaffeinated coffee or also known as decaf coffee still, has caffeine in its composition but at lower levels. In every 8-ounce cup of decaf coffee, there is around 0-7 mg of caffeine and contains an average of 3 mg. 
  • Espresso coffee this type of coffee is considered to be the strongest one among the others because it has more caffeine volume. Espresso is made by forcing hot water or steam through very finely ground coffee beans. Although it has a high amount of caffeine, its servings are small; it is estimated that every 30-50 ml has 63 mg of caffeine. 
  • Espresso-based drinks – lattes, cappuccinos, macchiatos and Americanos are just some of our favourite drinks that can be regularly bought in coffee shops. All of these have espresso shots mixed with a considerable amount of milk. Milk generally does not contain any caffeine; however, espresso contains 63 mg of caffeine and 125 mg for large servings. 
  • Instant coffee – this one contains less caffeine compared with brewed coffee, considering most of us actually consume this. An 8-ounce cup of instant coffee has an estimated 62 mg of caffeine. Instant coffee is the easiest to prepare among the rest since you just need to add the coffee powder with hot water. 

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Is there such a thing as too much caffeine?

An acceptable amount of caffeine to consume is 400 mg per day [6]. This is commonly around 4 to 5 cups of brewed coffee, ten cans of soda or two shots of energy drinks. Experts suggest that with this amount of caffeine, there are no dangerous and harmful side effects to experience. Significantly, you will not develop any brain and digestive problems. Although caffeine has its perks, it can cause several problems for you, too. 

Furthermore, caffeine’s major negative effect is that it can cause sleep deprivation in people who constantly consume it. There are also strong tendencies to feel fatigued at all times, develop sleeping problems like insomnia, struggle with memory and problems with regulating emotions [7].

Surprisingly, there are people who become sleepy when taking caffeine; this is because caffeine gives them the feeling of tiredness rather than being alert. The truth about caffeine and sleep is that it becomes a cycle when you depend too much on it. 

As caffeine can cause sleep deprivation for a day, you will probably feel tired and want to sleep more the next day you wake up; you will definitely want to consume caffeine to fill the need–and this is how the caffeine dependency starts. It’s time to end the cycle and make sure you get the rest you need.

If you are thinking of when to drink and when not to, there is a recommended cut-off time for caffeine intake. A minimum of 6 hours before bedtime is recommended if you want to balance your caffeine consumption. 

To know if you are overusing caffeine or become fully dependent, you should look for these signs: 

  • Constant headaches
  • Having anxiety during the day
  • Trouble sleeping during the night (frequent awakenings and trouble getting back to sleep)
  • Nighttime anxiety
  • Excessively sleepy during the day
  • Fatigue and tiredness
  • Low energy

While most of us have incorporated drinking caffeine into our daily routine, we need to be aware that too much can be bad news for our sleep, mood and health. Keep an eye on the number of cups of coffee you drink in order to prevent its possible adverse side effects. 

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The information included in this article is for informational purposes only. The purpose of this webpage is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.