Caffeine
Caffeine, found in coffee and tea, is the world’s most widely used stimulant; it blocks adenosine receptors to increase alertness and reduce perceived fatigue, indirectly raising dopamine and norepinephrine. Moderate intake is well studied and associated with improved attention and reaction time and, observationally, with lower risk of several chronic diseases. Downsides include tolerance, dependence with withdrawal headaches, anxiety and insomnia at higher doses, and disrupted sleep when taken late.
Too little may be associated with
Grogginess for habitual users; no true requirement.
Too much may be associated with
Anxiety, insomnia, palpitations, dependence.
Informational only — not medical advice.
Body systems
Functions
- Appetite Regulation (−)
- Arousal (+)
- Circadian Rhythm Regulation (−)
- Hunger Regulation (−)
- Motor Control (+)
- Sleep Regulation (−)
- Voluntary Movement (+)
- Wakefulness (+)
Hormones
Neurotransmitters
Research (11)
- Evidence-based cesarean delivery: postoperative care (part 10) Mackeen et al. (2025)
- YAP/TAZ Signaling in the Pathobiology of Pulmonary Fibrosis Papavassiliou et al. (2024)
- Current coffee consumption is associated with decreased striatal dopamine transporter availability in Parkinson's disease patients and healthy controls Wang et al. (2023)
- How to Optimize the Effectiveness and Safety of Parkinson's Disease Therapy? - A Systematic Review of Drugs Interactions with Food and Dietary Supplements Agnieszka et al. (2022)
- Role of diet in hyperuricemia and gout Danve et al. (2021)
- The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review Anas et al. (2021)
- Angiotensin II for the Treatment of Vasodilatory Shock Khanna et al. (2017)
- 36th International Symposium on Intensive Care and Emergency Medicine : Brussels, Belgium. 15-18 March 2016 Liu et al. (2016)
- The mitochondrial deubiquitinase USP30 opposes parkin-mediated mitophagy Bingol et al. (2014)
- Are we dependent upon coffee and caffeine? A review on human and animal data Nehlig (1999)
- [Coffee and health] Czok (1977)
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