What is Caffeine?

It is a natural stimulant widely found in coffee, cacao, and tea plants. It stimulates the central nervous system and the brain and helps you to remain alert, while also preventing fatigue.

According to history, the very first tea was brewed in 2737 BC (1).

It was discovered by a shepherd in Ethiopia who observed that it gave his flock extra energy. And then in the late 1800s, caffeinated soft drinks came on board, followed by energy drinks.

Currently, over 80% of the global population takes at least one caffeinated product each day. In North America, over 90% of adults take caffeinated products daily (1).

How Does Caffeine Affect Your Brain?

After caffeine is consumed, it is absorbed from the digestive system into the bloodstream. Once in the bloodstream, it moves to the liver and is metabolized (broken down) into very simple compounds that can affect your organs and how they function.

However, the main effect of caffeine occurs in the brain. Caffeine blocks adenosine’s effects. Adenosine is a neurotransmitter that causes your brain to relax and gives you that tired feeling (2).

Normally, the levels of adenosine in your body build up over time, causing you to feel tired and giving you that sleepy feeling.

But caffeine will keep you mentally alert and awake by binding to adenosine receptors but without activating them. This will block adenosine’s effects, thus reducing tiredness (3).

Caffeine also increases the level of adrenaline in the blood, along with the activities of norepinephrine and epinephrine in the brain (3).

This stimulates the brain and triggers a state of alertness, focus, and arousal. Caffeine is classified as a psychoactive drug because of its potential to affect your brain. Also, caffeine is “quick-acting.” For example, the amount of caffeine present in a cup of coffee can reach your bloodstream within 20 minutes, while its full effects can be felt within an hour of taking it (1).

Foods that Contain Caffeine

Caffeine is found naturally in nuts, leaves, or the seeds of certain plants. These sources are then harvested and processed, resulting in the production of caffeinated beverages and foods.

Below, we have the amounts of caffeine you may get per 240ml serving of some beverages (1):

• Coffee: 102-200mg
• Espresso: 240-720mg
• Energy drinks: 50-160mg
• Yerba mate: 65-130mg
• Chocolate milk: 2-7mg
• Cocoa beverage: 2-7mg
• Decaffeinated coffee: 3-12mg
• Soft drinks: 20-40mg

You can also find caffeine in some foods. For example, an ounce (28g) of milk chocolate contains 1-15mg, while an ounce of dark chocolate will provide 5-35mg (4).

Caffeine is also present in some over-the-counter drugs or prescription drugs like pain, allergy, and cold medications. It is also used in weight loss supplements.

Other Health Effects of Caffeine

Boost fat burning and metabolism

Because of the stimulating effect of caffeine on the central nervous system, it can boost metabolism by at least 11%. It also boosts fat burning by 13% (5,6,7).

Note that daily consumption of 300mg of caffeine may cause a burning of an extra 79 calories (8).

It may seem like a small amount, but it is similar to the excess calorie that causes an average yearly weight gain of 1kg (2.2 pounds) in Americans (9).

What are the Recommended Dosages?

According to the US Department of Agriculture and European Food Safety Authority, taking 400mg of caffeine daily is “safe.” That’ll be 2-4 cups of coffee daily (10).

As much as possible, try not to overdose on caffeine. Limit the amount you consume at a time to 200mg (11,12).