Caffeine is a naturally occurring stimulant that can be found in over sixty plants. Caffeine can also be created synthetically and subsequently added to foods. Early anecdotal effects included such symptoms as eased fatigue, improved mood and enhanced awareness. Common sources of caffeine include instant coffee (40-108 mgs per 8 oz), fresh brewed coffee (110-250mg per 8 oz), espresso (100mgs per 2 oz), tea (20-50 mgs per 8 oz) and cola (40-49 mgs per 12 oz).
Before discussing caffeine’s effect, remember it is a restricted or banned substance for many sport institutions because of its role in performance enhancement. As always, the rules of competition and if supplementation is permissible. The WIAA identifies caffeine as “restricted”. This means that products including caffeine can be legally purchased by and for an individual, but are prohibited in connection with school programs. Some products include but are not limited to, caffeine-enhanced products, energy drinks (e.g., Red Bull, Amp, Advance by Powerade, 5-hour Energy), herbal caffeine, No Doz and other substances as identified in the materials.
When ingested, caffeine causes a decrease in two neurotransmitters responsible for promoting sleep and causing an overall calming effect. More specifically, caffeine is a central nervous system stimulant. Additionally, caffeine has a glycogen (stored glucose) sparing effect, saving glycogen stored in muscle and liver tissue. At the same time, it activates an enzyme that increases adipose (stored body fat) breakdown and utilization. This means that caffeine supplementation can preserve energy stored in the muscle and liver, and at the same time increase energy provided by body fat stores. This was demonstrated in studies using abnormally high levels of caffeine, but the degree to which the body is effected is not well known.
Caffeine supplementation also has some associated negative side effects. When caffeine wears off, hormonal changes cause a drop in neural activity, lowering heart rate and blood pressure, and eliciting a perceived drop in energy. The subsequent fluctuations in energy levels can lead to a dependence on caffeine for a perception of “normal”. High levels of caffeine supplementation (300-500 mg/day) can cause blood sugar levels to fluctuate, causing false hunger or sugar cravings, irritability, gastrointestinal discomfort, and even changes to reaction time and perception. Additionally, caffeine has a dehydrating effect, requiring approximately 16 oz of water to rehydrate after consuming approximately 150 mg of caffeine. Cortisol, a steroid hormone associated with stress, also can increase with regular ingestion and withdrawal.
Journal articles suggest some consensus on caffeine supplementation. Caffeine can and does enhance performance, especially those of a shorter duration (ie < 1hr). Individuals performing endurance events or exercise have demonstrated a delayed onset of fatigue. However, the overall effect is very small, usually measured in seconds. Events lasting less than 30 minutes have the most positive results. Research also suggests that dose volume and dosing schedule are very important. While doses over 350 mg/day risk negative effects, suggested dosages for performance benefits often approach or exceed recommended levels. Additionally, individuals should try to refrain from supplementation for at least 3 days prior to the event to maximize effects. Caffeine is readily absorbed and should be consumed approximately 20-60 minutes prior to the event or workout. The peak effect occurs around 2-3 hours, after which, there is a perception of decreased performance. However, the half-life of caffeine is approximately 4-6 hours, meaning individuals perceive a drop in performance, but half of the dose is still being processed. This perception can lead to over-dosing, eliciting the negative side effects and hindered muscle recovery. There are general recommendations to follow to optimize caffeine supplementation, such as:
- Daily dose should remain at or below 350 mg.
- Don’t consume after 6pm to minimize effects on daily sleep patterns and promote adequate rest and recovery.
- Avoid daily consumption of a “pre-workout”, which typically contains high amounts of caffeine, and can cause dependence on caffeine for performance.
- Supplement shortly before an event, 20-60 minutes prior to, and emphasize hydration to combat the dehydrating effects.