Few things are as proverbial as a runner with a cup of coffee. Before a run. After a run. Or both. Yet even as major brands like GU Energy and Power Bar Gel make products with added caffeine, confusion remains. Isn’t coffee a diuretic? Doesn’t it promote dehydration? Won’t the caffeine make you jittery? Does it even make a difference?
The answer to the coffee question—which is really just the caffeine question in liquid form—is simple. Caffeine improves athletic performance, especially in endurance athletes. But as it is with so many things in life and sport, the key is in the details.
The research into the relationship between caffeine and athletic performance is extensive, reaching back to the 1970s. The data fills the archives of medical journals and sports nutrition societies across the globe, and it is conclusive. Caffeine is a proven and effective ergogenic aid, one of the few “legal performance enhancers.” Yet the benefits are not linear; more is not necessarily better, and the advantages of consuming caffeine are not distributed evenly across the board to every sport or even to every athlete.
Furthermore, coffee and caffeine are not synonymous. Coffee contains hundreds of compounds that are metabolically distinct from caffeine, and studies have shown that anhydrous caffeine (caffeine apart from any water) is more effectively absorbed and utilized by the body than caffeine contained in a liquid.
But enough with the disclaimers. We’re runners. We love our coffee. And we want specifics. How does coffee affect a distance runner, and how much can we drink?
The benefits of drinking coffee are predicated on an athlete consuming what medical journals call a “low-to-moderate” amount of caffeine, generally designated at 3-6 milligrams per kilogram of body weight. For a runner weighing 150 pounds, or 68 kilograms, the conversion is as follows:
Consuming over 9mg/kg has been shown to have detrimental effects on an athlete’s performance. For a 150-pound runner, that means 600mg is the tipping point, though it may be much earlier, depending on the person. On the flip side, athletes can benefit from as little as 1-2mg of caffeine per kilogram of body weight, meaning that even 80mg of caffeine can boost performance.
The amount of caffeine in a cup of coffee fluctuates to an absurd degree, making estimations difficult and ballpark, at best. But as a rule, an 8-ounce cup of regular coffee contains 100-180mg of caffeine. (For example, 8 ounces of Starbucks regular brewed coffee contains 180mg of caffeine.) Using the same 150-pound runner as the guideline, two 8-ounce cups of Starbucks coffee works; three is flirting with the edge.
But let’s assume moderation is exercised (no pun intended). How does the caffeine in coffee benefit runners specifically?
Improves endurance and decreases perceived effort. Studies show that caffeine decreases perceived effort by about 6%, which translates into an average overall performance improvement (both intensity and duration) of 12%. The increased performance is most prominent in endurance athletes engaged in extended exertion.
Increases mental alertness. Further tests in a variety of sports—from endurance cycling to team sports—have shown that athletes who consume caffeine before engaging in activity have heightened awareness and are able to think more quickly in cognitive tests.
Accelerates recovery, most notably in the replenishment of glycogen stores. This one is fascinating! Glycogen in the muscles is vital to success in distance running. Many bad workouts or marathon blow-ups are the result of glycogen depletion. In a recent study from Australia, researchers discovered that athletes who consumed caffeine along with their post-workout meal had 66% more glycogen in their muscles than those who consumed carbohydrates alone. They found that the caffeine increased the concentration of glucose and insulin in the bloodstream, speeding the body’s ability to absorb carbohydrates and restoring glycogen stores at a faster rate. Furthermore, researchers at the University of Georgia recently found that athletes who consumed caffeine before exercise reduced post-workout soreness by 50%.
Accelerates the body’s ability to convert carbohydrates to energy. Brands such as GU, Power Bar Gel, and Accel offer gels and chews with added caffeine, not only for the obvious benefits of the stimulant, but also to optimize the carbs contained in the products. Caffeine also helps the muscles release stored calcium, which further boosts endurance and speed.
Helps muscles burn fat as fuel. Researchers have found that while caffeine speeds the conversion of carbs into energy, it also preserves glycogen stores by causing the muscles to burn fat as a source of energy instead of the glycogen stored in the muscles.
Does not act as a diuretic when consumed in moderate amounts. Studies have shown that most people can consume up to 550mg of caffeine (three or four 8-ounce cups of coffee) without experiencing any diuretic effects. In fact, while scientists can’t quite pin down the mechanisms, they have found that exercise inhibits caffeine’s effect on the kidneys, erasing the diuretic effect. In other words, coffee is not liquid dehydration.
So what’s the catch? Well, coffee is coffee. The benefits are there for the taking, but it’s not a miracle drug. And you can have too much of a good thing; moderation is key if you want coffee to enhance, not hurt, your training. We recommend using common sense (and perhaps a touch of sugar and light cream) as you decide how much joe works for you. Keep in mind: