Base Knowledge: Caffeine

Up close and personal with the world's favorite energy booster.

The Upshot, Upfront:

• Caffeine is a safe, proven ergogenic aid—meaning it helps you exercise.

• It impacts everyone differently.

• Start with about 150 milligrams, one hour before you need it—and experiment from there.

The coolest thing about caffeine as a sports supplement is that the effects are obvious. Just like Popeye and his spinach, when it works, you know it. (As does Bluto.) With such visceral results, there’s no point in getting all sciencey on the topic, right?

Wrong!

The research behind caffeine is bountiful and groovy, so let’s take a moment to geek-out about its buzzy magic.

What is caffeine?

Caffeine—or as you may know it, C8H10N4O2—is a stimulant that’s been in use for thousands of years, most of them clouded in controversy. It’s been banned by several governing bodies including the leaders of the Church of Latter-day Saints, Islam, and the World Anti-Doping Agency (WADA). The Muslims reversed their ban about 500 years ago. Shortly thereafter, WADA took caffeine off its banned substance list in 2014. The Mormons aren’t budging.

Humans have a complex relationship with caffeine. It’s simultaneously addictive, beneficial, and accepted. As food (and drug) writer Michael Pollan says in his super excellent book, This is Your Mind on Plants:

“Few of us even think of it as a drug, much less our daily use of it as an addiction. It’s so pervasive that it’s easy to overlook the fact that to be caffeinated is not baseline consciousness but, in fact, an altered state. It just happens to be a state that virtually all of us share, rendering it invisible.”

The exception to this is the caffeinated athlete, a subset of humanity well aware of that “altered state.” For anyone who’s ever used caffeine to crush a workout or a competition, it’s anything but invisible.

How does caffeine affect you?

In the fitness world, caffeine is known as an “ergogenic aid,” meaning it improves athletic performance. How it does this isn’t completely understood, but one thing we’re certain about is that it blocks adenosine receptors.

Adenosine is an inhibitory neurotransmitter. That means it attaches to receptors in the central nervous system in order to cause fatigue.

The chemical structure of adenosine is C10H13N5O4. As you may recall from my lame chemical structure joke earlier, caffeine is C8H10N4O2.

Same same but different! In fact, they’re so same same that caffeine can attach to those receptors in place of adenosine. When adenosine can’t do its job, fatigue is delayed. When fatigue is delayed, performance improves.

There are a few other hypotheses as to the ergogenic magic of caffeine. One is that it stimulates fat burning, which preserves glycogen so that you have access to more fuel over the course of your effort. Another is that it releases extra calcium into your system, stimulating muscles. Either way, if you asked me in an elevator to explain how caffeine works, I’d go for the adenosine receptor thing, so let’s stick with that.

Coffee and tea achievers know that you can build up a tolerance to caffeine over time. The general consensus in the sports world is that a tolerance from moderate use of caffeine shouldn’t impact its effectiveness as an ergogenic aid that much.

By “that much,” I mean the tolerance might impact the benefit a little, but the side effects of withdrawal (headaches, et al.) aren’t worth the marginal performance gains that you earn from going cold turkey, so don’t bother.

That said, this brings to light the fact that caffeine is addictive. Whether or not this is okay with you is your call.

Your genes on caffeine.

Your DNA impacts the way you absorb caffeine. Thanks to a gene called CYP1A2, some people are slow absorbers, others are fast absorbers.

How CYP1A2 impacts caffeine’s influence on your workout is TBD. Here’s a study on cyclists showing caffeine only benefits fast absorbers. Here’s another study measuring effects on resistance work, jumping, and sprinting that says genes don’t matter. Here’s a review of a bunch of studies corroborating that caffeine benefits exercise across the gene pool.

For what it’s worth, I’m a caffeine slow absorber. (CYP1A2 AC/CC genotype and proud!) I know from personal experience that caffeine doesn’t do much for my workouts right out of the gate, but after a couple hours of riding/running, it gives me the endurance to keep going.

Is caffeine bad for you?

For most people, caffeine in moderation is fine. However, caffeine is a drug and, like all drugs, too much can be harmful. Luckily, it’s been shown that low-to-moderate caffeine intake is just as effective as mega-dosing when it comes to exercise.

Of course, if you’re pregnant or breastfeeding or you have cardiovascular or gut issues, you’ll want to talk to your doctor. Other than that, if caffeine isn’t right for you, it’s obvious. You get nervous. You get stomachaches. You can’t sleep. If it makes you feel bad, don’t consume it.

And keep in mind that different strategies can have different results. Maybe coffee doesn’t agree with you, but a caffeinated sports supplement does. Or maybe there’s a time cut off. Personally, I rarely consume caffeine in the afternoon if I plan on sleeping that night.

How much caffeine do you need?

Short answer: none. You don’t need caffeine.

But if you want to take it, the generally accepted recommendation pre-workout is 3-6 mg/kg of body weight—although even 2 milligrams has been shown to work. (If you’re reading this from the United States, divide your weight in pounds by 2.2 to figure out your kilograms.) 9 mg/kg is where things start to get dangerous. And the FDA states that 1,200 mg at once is flat-out toxic.

Again, there’s no performance benefit to overdoing it, so don’t. Please.

Most people I’ve worked with do great with that 2 mg/kg, so I recommend starting there. To put it into context, this would require a 175-pound athlete to drink about 12 ounces of brewed coffee, which is around 150 mg of caffeine.

When should you consume caffeine?

For most, caffeine peaks in your blood about an hour after you take it with a half-life of about five hours on average. But those numbers vary wildly depending on your genes and how you consume it, so use this as a baseline and experiment from there.

It’s important to remember that you’re taking caffeine for future-you. If you’re taking it pre-workout, keep in mind that you’re probably not going to start at 100% so you won’t benefit from peaking at the beginning of your activity. Account for the time you’ll spend warming up.

If you’re taking it in the middle of an activity to prevent fatigue, try to guess when you’ll be on the ropes and take it an hour before. Same if you’re looking for a mid-game performance boost. For example, if you’re racing gravel and you know there’s a big climb ahead, estimate how long it’ll take you to get there and knock back that Americano an hour or so before.

(I cite this example assuming that future-you attends gravel races with an espresso machine in the feed zones because, well, that’s just civilized.)

By now, I hope you’re seeing a theme. The science behind caffeine is solid and extensive, but everyone reacts to it in different ways. Fortunately, those ways tend to be super obvious, making it really easy to road test different methods until you find the way that best impacts your training.

So get to work and let us know what you learn!