Does caffeine affect athletic performance?

Originally Published: September 26, 2003 - Last Updated / Reviewed On: June 13, 2011
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I play on the varsity soccer team. My team's coach and captains have told us not to drink beverages with caffeine because they dehydrate you. Is this true? Are there any other harmful effects of caffeine on athletes?

Dear Reader,

Your coach and captains may be correct. However, the literature is inconclusive. Some research suggests that caffeinated products increase urination, causing the body to void needed fluids and become dehydrated. On the flip side, the literature also suggests that no immediate diuretic effect on the body follows the ingestion of caffeine, as the total amount of fluid from the caffeinated beverage usually compensates for the expelled liquid.

Caffeine has been considered an ergogenic aid — a drug that increases performance as a result of the physiological effects it has on the body. While the exact mechanism isn't known for sure, some researchers believe that caffeine stimulates earlier and greater fat burning during exercise. This would help preserve the body's store of glycogen (the fuel muscles use) so that a person could exercise longer before feeling exhausted. This theory supports findings that caffeine improves performance in endurance events, such as long distance running and/or cycling. It hasn't been proven to aid athletes in shorter or more sporadic activities, including soccer. Others believe that the stimulant effect of caffeine may help with alertness, mental clarity, and overall mood, all of which could help during a workout.  For more information, check out Red Bull & weight loss from the Go Ask Alice! archives.

However, caffeine can affect people in different ways. While some people might notice a performance boost, others might suffer from dizziness, headaches, loss of coordination, abdominal cramps, or nausea — definitely not desirable on game day. Caffeine can also interfere with sleep patterns; overuse might mean that you're not well-rested enough when it comes time to play.

Caffeinated products probably aren't the best source of liquid to hydrate your body prior to an athletic endeavor. You'd probably do better to follow the advice of your coach and captains: focus your efforts on proper training, rest, and nutrition for optimal performance on the field. Read some of the Related Q&As listed below for better sources of liquids to keep you hydrated.