A new analysis of existing research suggests that the relationship between caffeine and athletic performance is more complex than many assume. The study indicates that the performance benefits of caffeine may plateau at relatively low doses, meaning that extra cups of coffee or high-dose pre-workout supplements may not provide a meaningful advantage.
Researchers analyzed 48 randomized, placebo-controlled trials involving 689 participants. The goal was to compare how different amounts of caffeine affected performance in aerobic time trials. The doses were categorized as low (up to 3 milligrams per kilogram of body weight), moderate (4 to 6 mg/kg), and high (more than 6 mg/kg). The analysis only included studies that used pure caffeine in capsule or liquid form to ensure consistent dosing.
The results showed that low doses produced a statistically significant improvement in completion time. Moderate doses also improved performance. However, the real-world difference between the two was small. Low doses led to an average improvement of about 2.14 percent, while moderate doses led to an average improvement of about 2.18 percent. This suggests that taking two or three times the amount of caffeine may not result in a noticeably faster finish.
The study also found that the results for moderate doses varied more across different trials, meaning the effect was less predictable. The low-dose group showed a more consistent effect. No studies using high doses met the criteria for the time-trial performance analysis, so the effects of very high doses remain unclear.
The review also highlighted the role of genetics. A gene called CYP1A2 controls an enzyme that breaks down most of the caffeine a person consumes. People with a specific variant of this gene, often called slow metabolizers, may not get the same performance boost from caffeine. Other genetic factors, including variations in adenosine receptors, may also influence how the body responds to caffeine.
For someone who weighs about 70 kilograms, a low dose would be between 90 and 210 milligrams of caffeine. A standard cup of coffee typically contains 80 to 200 milligrams, depending on how it is brewed. This means a single morning cup may already provide the amount of caffeine linked to the performance improvements seen in the study.
Higher doses of caffeine are linked to side effects such as anxiety, heart palpitations, headaches, poor sleep, and stomach problems. Because moderate doses offered only a small real-world advantage over low doses, the study’s authors suggest that starting with a lower amount is a reasonable approach for most people.
