We all drink coffee (or avoid it!) for different reasons. Caffeine is one of the common considerations people talk when ordering their coffee. So today, we’re discussing what it is, how it operates in us, and how much can be found in coffee.

What is caffeine?

Most of us are familiar with that morning brain fog. Then we either visit the nice barista in town or prepare for ourselves a nice cup of coffee or shot of espresso. By the time the cup is about halfway down, we feel better already—thanks to caffeine. Let’s go over the four compounds that impact our caffeine experience!

1. Adenosine

Caffeine acts on the body by blocking adenosine receptors in the brain. Adenosine is the chemical that helps us fall asleep at night. When adenosine does successfully bind to our body’s receptors, it slows us down by lowering blood pressure and dilating blood vessels. This brings more oxygen flow which means more sleepiness. Caffeine shares a similar chemical structure with adenosine which is why it can also bind to those receptors, but preventing the effects of adenosine from taking place. Because there are fewer active receptors, neural activity speeds up, which is the feeling of alertness we experience. It’s for this reason that we should avoid caffeine if it’s sleep we’re looking for.

2. Adrenaline

What is the byproduct of more brain activity? Adrenaline! Our body isn’t able to distinguish certain thoughts so much as the fact that we’re having many of them. As our mind begins to race, our body believes something is happening that requires energy. This is when it starts releasing doses of adrenaline into our body—perfect time for a workout. However, when the energy isn’t expended, our body finds a way to release it. How you ever found yourself foot-tapping, pencil-spinning, or just plain excited?

3. Dopamine

We now know caffeine blocks adenosine receptors in our body to prevent us from feeling tired. In addition, caffeine also prevents our body from breaking down dopamine. Dopamine is that happy chemical in our body. While caffeine doesn’t produce dopamine, it just help our body experience this feel-good compound for longer; and who doesn’t like more happy?

4. Theophylline

Theophylline is a bronchodilator which means it opens up our air pathways. It also relaxes our blood vessels and smooth muscles. Technically, caffeine is not related to the compound theophylline, but its chemical structure is so strikingly similar that our body may interpret it as theophylline.

Caffeine content in coffee

Each cup of coffee varies due to the bean type, roast method and brew method. Generally, caffeine content is higher in coffee brewed by immersion, like cold brew. When it comes to varietals and roast levels, things get a little tricky.

A study of an Arabica variety and a Robusta variety roasted to light, medium, and dark levels showed interesting results. When brewed using a filter method, the Arabica variety showed least caffeine content when roasted medium, more caffeine when roasted light, and most caffeine when roasted dark. In the Robusta variety, however, the caffeine content increased as the roast got darker.

On the other hand, when the same Arabica samples were brewed by boiling, the light roast sample produced most caffeine and medium roast produced the least. The opposite was true of the Robusta variety - caffeine levels were highest in the medium roast and lowest in light roast. Across the board, boiled coffee of every roast level had more caffeine than its filter-brewed than its same level-roast counterpart.

How long does caffeine last?

It takes about 45 minutes for 99% of the consumed caffeine to be absorbed. In an average individual, it takes about 4-6 hours of half of the consumed caffeine to metabolize. This is known as the “half-life”. In order for all of the caffeine to be metabolized by the kidney and passed through the body through urine, it can take up to double that. This metabolism occurs in a downward curve. That is the point where most experience a “crash” because the elevated levels of adenosine are now able to attach themselves to the brain’s receptors. Dopamine is also now able to break down at a normal rate, so the feel-good chemicals also dissipate. As a result, our bodies may suddenly feel tired.

Why do coffee plants have caffeine anyways?

While coffee isn’t the only plant that has caffeine (think: cacao, camellia sinensis [i.e., tea], yerba mate, etc.), it exists as a part of nature for a reason. It is actually an effective pesticide. A person needs to consume around 10 grams of caffeine to experience the dangerous effects of overdose, such as irregular heartbeats and panic attacks (side note: typically, a “cup” of coffee contains 95 milligrams of caffeine; 3 cups of coffee is less than 3% of that threshold). On a tiny insect, it only take a little amount for it to be effective. As nature would have it, bugs have receptors that are able to detect whether caffeine is present in what they’re eating so it’s not long before they try their hand with a coffee plant that they turn the other way. In addition, as coffee plants drop their leaves, it leaves traces of caffeine in the soil which help it to grow well while deterring other plants in its surroundings.

In the end

Legend has it that coffee was first discovered in Ethiopia because of goats that loved the jitters of caffeine. From ancient to modern times, we’ve found that caffeine does wonderful things for most of us (think: reduces the risk of some cancers, decreases the risk of strokes and Type 2 diabetes, improves memory) but is best when balanced like a good espresso.