Here are some thoughts regarding the America's most popular psychoactive drug - caffeine. It's one of my favorite substances, and I know lots of you probably have a similar affinity for caffeine. We all understand the basic relationship between "drink caffeine" and "get hyped up", but it might be interesting to look at some of the nuances and less known effects of caffeine.
I may not be a doctor, but I am a scientist ;) And I ingest a substantial amount of caffeine on a daily basis. So now that I have thoroughly proven myself to be an authority on the subject, here goes:
We'll go over some biochemistry, general effects of caffeine, and effects on endurance athletic performance...
Caffeine is a naturally occurring stimulant with the chemical name trimethylxanthine and formula C8H10N4O2. 80% of Americans ingest caffeine on a regular basis, mostly through beverages such as tea, coffee and energy drinks. But let's be real - it's all about the coffee. Over half of us drink coffee every morning, and 80% of Americans label themselves as 'coffee drinkers'. You find coffee in every locale at any time of day - brewing on your kitchen counter, at the corner store, at work, in the hands of commuters, during your 11am slump, during your 2pm slump, and at 10pm to kick start your night out (okay, maybe that's just me, and maybe not a great idea). Point is, caffeine, and particularly coffee, is ubiquitous and America would darn near grind to a halt without it.
The next three sections of this post examine what caffeine actually does to us (in a biochemical sense), what that means for general caffeine use, and what that means for athletic caffeine use.
Science - Why Do We Love Caffeine? (or, why does it work?)
Caffeine's popularity is generally attributed to the increase in energy and feeling of alertness that follows adequate consumption. Caffeine can provide these effects by imitating the chemical adenosine. Adenosine is a naturally occurring chemical in humans that binds to certain receptors in the brain and induces drowsiness by slowing down nerve cell activity. Caffeine counteracts drowsiness by binding to adenosine receptor sites, thereby blocking adenosine from reaching the site. The caffeine does not directly stimulate your nervous system, but it prevents adenosine from depressing nerve cell activity. The lack of a depressing force allows the nervous system to speed up and creates a feeling of alertness.
Here is my poorly constructed analogy:
You're throwing a party and are trying to get it rockin. You've got a friend named Nerves, and Nerves is the DJ for your party. Nerves' default mode is to play jukin' music that is going to turn your party into a rager. You've got another friend, Adenosine, that just wants to keep things calm and have some pleasant conversation. If you let him, Adenosine will walk over to Nerves, recommend he play some Colbie Caillat, and kill your party. Good thing you have your square-shouldered friend, Caffeine. You invite Caffeine over, he'll shove Adenosine in the corner and allow Nerve to go about his work unobstructed.
Adenosine is there to slow your nervous system down. Caffeine doesn't directly stimulate you - it just prevents adenosine from doing its job. By blocking adenosine, caffeine allows your body/nervous system to go to it's default mode - full throttle. Rage on.
Most of us drink caffeine pretty much on the regular. It's not complicated - drink caffeine, feel energized. Well, let me complicate it so you have something to think about next time you reach for your morning fix.
-Depending on your tolerance, 30-150 mg of caffeine is going to have a noticeable effect on you. More than 400 or 500mg and your likely going to be pretty uncomfortable.
-Drinks vary greatly in their caffeine content. Some examples:
Two points to keep in mind:
-Drinks vary greatly in their caloric content. Most calories in caffeinated beverages are straight sugar. That's bad if you don't eat anything with it, because you are going to get a fantastic blood sugar spike, insulin response and subsequent sugar crash. It's also going to contribute to, one day, making you insulin resistant. Finally, drinking your calories doesn't really satiate you, so you are likely to overdo your caloric intake.
-The half-life of caffeine in humans seems to be around 5-6 hours. That means if you drink your 16 oz redeye (16 oz coffee + 1 espresso shot = 400mg caffeine) at 10am, your blood caffeine levels will be 200mg at 4pm and 100mg at 10pm. That 6 hour half-life is way longer than most people realize. If you're having trouble falling asleep at night, you might want to take a look at your caffeine intake. Take the above example of the strong coffee at 10am - if you are then trying to go to sleep 12 hours later, at 10pm, you still have 100mg of caffeine floating around in your bloodstream. That's the same as downing a 10oz mug of coffee immediately before getting into bed and then wondering why you can't fall asleep.
I'm not saying that you shouldn't drink plenty of coffee. You should. It's generally a positive thing. And of all the vices we could feed, caffeine seems pretty innocuous. Just watch the sugar content and time of day.
-And a potential health bonus: Caffeine appears to increase the thermic effect of a meal. In other words, compared to sans-caffeine, ingesting caffeine with/near a meal causes you to immediately burn more of the calories from that meal than normal, potentially leaving less to be stored as fat.
Consumption for Endurance Athletic Performance
Some of caffeine's effects sound pretty appealing for an endurance athlete - decreased drowsiness, increased alertness, increased focus, increased energy. Several scientific studies have looked at caffeine's role in athletic performance, and, while there is some conflicting evidence, caffeine does seem to provide a performance advantage.
Caffeine is a cardiac stimulant, a mild diuretic and provides a “boost of energy” in humans. Let's examine these in relation to endurance athletics.
-Cardiac stimulant. Because of it's effect on your central nervous system, caffeine tends to temporarily increase both your blood pressure and heart rate. That actually doesn't affect athletic performance a whole lot - your heart rate is just going to be a bit higher at a given power output.
-Mild diuretic. Hydration is of utmost importance in endurance events, so diuretics maybe don't sound like a great idea. However, it is not a very strong diuretic, and humans seem to develop a resistance to caffeine's diuretic effect with repeated exposure. So, for a regular caffeine user, the diuretic effect during an athletic performance is going to be negligible.
-"Boost of energy." Studies have found that the most significant performance enhancing effect of caffeine is likely due to perceived exertion. The higher your perceived exertion, the tougher it is to continue at your current effort. If you feel like you are going at an 8/10 effort, you're not going to last as long without slowing down as you would if you feel like your going at a 7/10 effort.
A study was conducted that had cyclists pedal until exhaustion at a specified power level. Compared to cyclists that were given caffeine-free drinks, cyclists that were given caffeine reported lower levels of perceived exertion at the same power output. And, most importantly, the caffeine-ingesting cyclists lasted longer at that power output before exhaustion.
-One final effect is that caffeine may increase your rate of fat metabolism. That is potentially an advantage in a ultra-distance event. You only have so many stored carbohydrates (2,000-3,000 calories), but even the leanest athlete has 20,000+ fat calories available. If you can increase the rate at which you use those fat calories, you can potentially prolong your carbohydrate stores and race faster for longer.
That's that. Go gung ho. Rip some espresso shots, brew a gallon of tea, crack some redbulls and reap the rewards of increased alertness, increased metabolism and potentially greater endurance.
But take 'er easy pal. Caffeine is a serious substance. It's a cardiac stimulant. Your pulse and blood pressure are going to increase, and extreme consumption can cause temporary arrhythmia. And there is a lethal dose, although it would be hard to accomplish just drinking lattes. And with regards to endurance sport use, 'lots' does not work any better than 'some'. The study that found that caffeinated cyclists outperformed their sober peers also found that high doses of caffeine did not increase performance any more than moderate (200-300mg) intakes.
So don't bother trying outrageous intakes on race day. I've tried it, and all it causes is some serious jaw clenching and getting friendly with half the port-a-johns along the race course.