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Caffeine: how it works and where it is found

Caffeine is an alkaloid found in both the seeds and leaves of coffee, tea, cacao, cola and mate plants. A cup of coffee contains about 50 mg of caffeine and its stimulant action, which lasts for one or two hours after it has been drunk, acts on the cerebrospinal nervous system, heightening our mental faculties, keeping away sleepiness, boredom, fatigue (including mental fatigue) and depression. It bolsters memory, learning capacity, perception and concentration, and facilitates the perception of sensory stimuli; it also abates headaches and migraines.

The scientific community agrees on the amount of caffeine that can be consumed in a day, indicating 300 mg/day of caffeine for an adult, i.e. about 4-5 mg of caffeine per kg of body weight per day: e.g.:
a man weighing 70 kg (154 lb) = 4.5 x 70 = 315 mg.

To get an idea of what it means in terms of dose, these are the quantities of caffeine contained in some of the most common beverages/foods:

  • Espresso or mocha coffee 40-80 mg per cup
  • American coffee 115-120 mg per cup
  • Instant coffee 65-100 mg per cup
  • Decaffeinated coffee < 5 mg per cup
  • Cappuccino 70-80 mg per cup
  • Chocolate 30-40 mg per 60-g bar
  • Tea 40-50 mg per cup
  • Cola drinks 35-50 mg per can
  • Energy drinks with caffeine or guarana 50-100 mg