The claimEvidence A · guideline-tier
Coffee fully covers an all-nighter
The evidence
Receptor ceiling is 400 mg. What coffee pushes through is the feeling of sleepiness, not the underlying impairment — working memory + error rate stay degraded.
The mechanism, in brief
You don't feel sleepy because adenosine is blocked, not because caffeine itself energises you.
Sources (2)
- Wesensten, N. J., Belenky, G., Kautz, M. A., Thorne, D. R., Reichardt, R. M., & Balkin, T. J. (2002). Maintaining alertness and performance during sleep deprivation: modafinil versus caffeine. Psychopharmacology, 159(3), 238–247.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. (2015). Scientific opinion on the safety of caffeine. EFSA Journal, 13(5), 4102.