The Science of Caffeine: What Is It Exactly?

This primer on a runner's favorite energizing compound breaks down exactly what caffeine is, common sources and some effects these sources have on the body.

What Is Caffeine & How Does It Work?

Many coffee-drinking runners may claim they don’t do drugs. But did you know that caffeine is an extremely potent psychoactive? The most widely taken drug in the world, we consumed over 100 tons of it in the popular form of coffee beans just in the last year!

Caffeine works by binding to the brain’s adenosine receptors. Adenosine is a molecule that activates feelings of tiredness when they bind to their respective receptors. Caffeine has the ability to bond with these same receptors, but not activate them the way adenosine does. This blocks the adenosine, which is trying to bind to their receptors in order to set off the sensation of tiredness. Therefore, you don’t get tired when you consume caffeine; it physically blocks the molecules that spark the mechanisms behind fatigue.

Sources of Caffeine:

Coffee (1 cup = roughly 95 mg caffeine)

Many of us can’t imagine starting our day without a cup of joe. This bitter bean juice is the most potent natural source of caffeine. Both “caffeine” and “coffee” share the same root word: the Arabic word qahweh — coffee was cultivated in North Africa as early as the sixth century.

Coffee beans have numerous health benefits that filter into your brew. For example, the standard cup can contain roughly 11% of your recommended daily intake of riboflavin, also known as vitamin B-2. This vitamin supports the formation and maintenance of red blood cells. A deficiency in B-2 can mean a deficiency in other nutrients too, as this essential vitamin is required for optimal processing of other nutrients.

Tea (1 cup = roughly 47 mg caffeine)

This aromatic elixir has been a dietary staple since antiquity, dating back thousands of years in what is today China, Tibet, Myanmar and India. The recipe itself is simple: fresh or cured leaves from the tea plant (Camellia sinensis) steeped in boiling water. But the varieties are expansive. The tea plant is the source of common varieties like white, yellow, green, oolong and dark tea. Steeped beverages similar to tea but not made from the tea plant are called “herbal teas,” to distinguish them from proper tea. These include plant and fruit blends like chamomile or rosehip.

Some teas — particularly black and green varieties — contain an amino acid not present in coffee: L-theanine. Tea drinkers find that L-theanine induces relaxation, mood-boosting effects and even concentration, balancing the stimulant effects of the caffeine. This means you can get your caffeine fix, minus the jitters, and improve focus on attentional tasks! While more robust scientific research is needed to back up these bold claims, some researchers and tea drinkers worldwide vouch for these beneficial effects.

Cola (12 oz can = roughly 30-40 mg caffeine)

If you’ve ever felt a surge of awakeness or energy after a can of cola, you may chalk this up to sugar rush. However, seeing that there is little scientific evidence behind the “sugar rush,” this effect is likely thanks to cola’s caffeine content. This is important to know for those looking to cut back on their caffeine intake.

You can already guess that Clean Eating is never going to advocate for drinking processed high-sugar beverages, but you should know why. Caffeine can be addictive, with users needing more and more for the same energizing effects over time. Sugar is also addictive, shorting the brain’s pleasure center and altering one’s ability to taste. This means caffeine-containing colas are doubly addictive. Plus, in 2005, a study conducted by Harvard researchers found that participants who drank the most cola increased their risk of high blood pressure by 16%-44%

What Do We Recommend?

We’re all java-lovers, as proven by our extensive coffee-centric coverage. And we’re big tea fans, too. But even we know when to cut back. Caffeine is addictive and you may require greater amounts for similar effects over time. If you’re prone to anxiety, this stimulant can exacerbate existing symptoms and induce new ones: jitteriness, excessive sweating, heart palpitations and insomnia, to name a few. When you feel yourself reaching for a second or third cup — particularly of coffee — in one day, consciously cut back by evaluating your lifestyle and seeing what other energy-boosting practices you can implement:

Oh, and no, we definitely don’t recommend cola.