Caffeine Tolerance in Endurance Sports: Does Habitual Intake Reduce the Effectiveness of Acute Supplementation?

Abstract

Background: Caffeine is a well-established ergogenic aid that improves endurance performance at acute doses of 3–6 mg/kg. Widespread habitual intake, mainly via coffee, raises the question whether chronic exposure blunts this effect. Aim: To critically assess whether regular caffeine consumption, particularly habitual coffee intake, modifies the acute ergogenic response to pre-exercise caffeine in endurance contexts. Methods: A structured, non-exhaustive search (January 2020–June 2026) was performed in PubMed/MEDLINE, PubMed Central, Scopus, Web of Science, and the Cochrane Library, with citation tracking. Priority was given to systematic reviews, meta-analyses, randomized placebo-controlled crossover trials, and prospective studies on endurance performance, habitual intake, and acute responses; mechanistic papers were included selectively. Results: Acute caffeine consistently enhances endurance performance. The largest meta-analysis indicates no significant attenuation of the pooled ergogenic effect with habitual intake. However, longitudinal data suggest that repeated daily exposure may reduce the magnitude of benefit over time without abolishing it, consistent with partial, context-dependent habituation. Inter-individual variability is influenced by dose, timing, delivery form, and training status; genetic effects remain insufficiently defined for clinical personalization. Conclusions: Habitual caffeine use does not eliminate the ergogenic effect of acute supplementation in most endurance settings, but may attenuate responsiveness in some individuals. Evidence supports individualized strategies based on habitual intake, prior response, timing, and tolerability rather than routine abstinence or dose escalation. Well-controlled longitudinal studies are needed to clarify the extent and mechanisms of habituation.