Cognitive performance is extensively perceived to be enhanced by caffeine intake and, more recently, a widespread support of its health benefits has been assuredly established: antioxidants, anti-stress agent, parkinson’s disease prevention, liver protection, mood enhancer, and a safe nootropic . However, how much is too much?
Up to 400 mg of caffeine per day (around two to three cups of brewed coffee) appears to be safe for most adults [Remember, though, that the amount of caffeine per coffee beverage varies accordingly its preparation and style]. Going further that amount, you are more prone to suffer from caffeine side-effects: increased heartbeat, heartburn/reflux, jitters/restlessness, and anxiety . Caffeine increases adrenaline, hence your senses become more heightened and you are more susceptible to muscle twitches and spasms. While for some people this stimulant effect can be useful for concentration, for others can be source of confusion and stuttering.
If you, like many adults, consume more than the recommended dosage of 400mg and you are not experiencing these above-mentioned side-effects, it does not mean that you are completely free of any health threatens. Caffeine withdrawal is now a recognized disorder, and is listed in the DSM-5. In this interesting paper named “Faster but not smarter”, researchers explain how caffeine abuse in the long-term can lead to greater sleepiness, lower mental alertness, and poorer performance on simple reaction time. While caffeine benefits motor performance, tolerance develops to its tendency to increase nervousness, hence its frequent over-consumption fails to enhance mental performance.