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Caffeine and L-Theanine for Athletic Performance: Are They Benificial?

March 31, 2026 - Admin
Search interest in caffeine and L‑theanine supplements has surged among athletes and fitness enthusiasts looking to improve strength, endurance, and mental focus. While caffeine is widely recognized as a powerful ergogenic aid, L‑theanine is often marketed as a compound that can smooth caffeine’s stimulating effects while enhancing concentration. But do these supplements actually improve athletic performance when taken alone or together?

 

Key Points

Moderate doses of caffeine (≈3 mg/kg) did not significantly improve strength, endurance, or coordination in competitive athletes. (Equivalent to 210 mg of caffeine based on 150 lb. adult.) Higher doses are likely more effective (≈6 mg/kg) approximately 400 mg of caffeine.

Acute intake of 200 mg L‑theanine was associated with lower maximal leg and back strength compared with placebo.

The combination of caffeine and L‑theanine did not produce synergistic improvements in physical or cognitive performance.

Supplement responses vary widely depending on habitual caffeine intake, individual physiology, and task‑specific demands.

 

Why Athletes Use Caffeine and L‑Theanine

Modern athletic performance depends not only on physical power but also on attention, reaction time, decision‑making, and visual‑motor coordination. Because of these demands, supplements that influence brain chemistry and alertness are frequently used in sports nutrition.

Caffeine: The Classic Performance Stimulant

Caffeine works primarily by blocking adenosine receptors in the brain, increasing dopamine and norepinephrine activity. These effects can reduce perceived effort, delay fatigue, and improve alertness during demanding physical activity.

L‑Theanine: Calm Focus Without Sedation

L‑theanine is an amino acid found naturally in green tea that increases levels of neurotransmitters such as, serotonin, and GABA. These neurochemical effects are associated with a relaxed mental state.

Study Design

In a randomized, double‑blind, placebo‑controlled crossover study, competitive athletes completed four separate supplement conditions: caffeine, L‑theanine, caffeine plus L‑theanine, and placebo. Performance tests evaluated maximal strength, intermittent endurance, and eye‑hand coordination.

Major Findings

Moderate Caffeine Did Not Improve Performance Outcomes

Under the conditions of the study, moderate caffeine did not significantly improve leg strength, back strength, handgrip strength, aerobic endurance, or eye‑hand coordination compared with placebo. A higher dose of caffeine may have been more effective.

L‑Theanine May Reduce Maximal Strength

Athletes who consumed L‑theanine alone demonstrated lower maximal leg and back strength values. This effect may be related to the compound’s calming neurological influence through GABA‑related pathways.

No Synergistic Benefit From the Combination

Despite common claims in supplement marketing, combining caffeine with L‑theanine did not produce additional improvements in strength, endurance, or coordination.

Practical Implications for Athletes

These findings suggest that the performance effects of caffeine and L‑theanine may be highly task‑specific. While caffeine is widely regarded as an ergogenic aid, its benefits may depend on dose, individual tolerance, and testing conditions. Meanwhile, L‑theanine may promote calm focus but could potentially reduce maximal force output when taken before strength‑based tasks.

Conclusion

Caffeine and L‑theanine are among the most widely consumed performance supplements, yet their combined effects may not be as beneficial as often assumed. In competitive athletes, the caffeine‑theanine combination did not significantly improve strength, endurance, or cognitive coordination.

 

REFERENCE:
Acute effects of combined and isolated caffeine and theanine supplementation on physical and cognitive performance in competitive athletes: a randomized, double-blind, placebo-controlled crossover trial.
Frontiers of Nutrition, January 25, 2026
Selin Yildirim Tuncer et al.