Caffeine is a natural stimulant that can improve cognitive ability, concentration and even acts as a pain killer.
It can be found in tea, coffee and even coca cola and is slightly addictive.
However, in larger amounts, Caffeine might start showing adverse effects. Larger amounts can increase body temperature and lead to involuntary muscle actions, twitching and cramping.
Further, larger amounts can even increase the heart beat.
Hence, it is recommended to stay within the daily caffeine intake limit.