Does coffee have negative effects on long-distance runners?

Race day has arrived. You're dressed in your running gear, clutching your lucky charm, and your bib is securely attached. After weeks of marathon preparation, could skipping your morning coffee have been a mistake?

Research on coffee often yields conflicting results. One moment, it's deemed harmful; the next, it's hailed for its numerous benefits. However, when it comes to caffeine, the findings are more consistent for athletes: it can enhance performance. Caffeine stands out as one of the few legal performance boosters globally. Numerous studies show that athletes who consume caffeine before competitions tend to perform better, endure longer, and recover faster compared to those who don't. While studies suggest a 20 to 25 percent improvement, real-world results might be slightly less pronounced [source: Kolata].

Caffeine offers multiple benefits for runners. Research indicates that it encourages muscles to burn fat instead of glycogen, enhancing endurance. Additionally, caffeine boosts muscle performance by releasing stored calcium, improving both speed and stamina. It also alters perceived exertion, allowing runners to push harder and longer without feeling as fatigued.

A small amount of caffeine is sufficient to achieve these effects. Studies suggest that 1 to 2 milligrams of caffeine per kilogram of body weight is optimal [sources: Kolata, Metcalf]. For example, a 175-pound (79-kilogram) individual would need about 350 milligrams, equivalent to roughly two-and-a-half cups of coffee [source: Metcalf]. However, exceeding 9 milligrams per kilogram can impair performance [source: Kolata].

For those unaccustomed to caffeine, side effects like jitteriness and headaches may occur. Non-coffee drinkers might want to avoid it on race day. Additionally, individuals with heart conditions or high blood pressure should consult a doctor before combining coffee with exercise.

Coffee can also cause gastrointestinal issues for some runners, such as diarrhea, while others use it to regulate their system before a race. To avoid surprises, it's wise to test your tolerance during training rather than trying coffee for the first time on marathon day. Contrary to common belief, coffee doesn't dehydrate you during exercise and may not even act as a diuretic, as physical activity seems to counteract its effects on the kidneys [source: Metcalf].

So, lace up your shoes and enjoy your coffee!