A family of substances: caffeine, theophylline and theobromine, which are derived from xanthine, are found in tea, coffee, cola and chocolate, and have pronounced physiological effects on the body.
Caffeine stimulates the central nervous system, while theophylline and theobromine stimulate the heart. Theophylline is also available as an anti-asthma drug.
There is some evidence that the consumption of methylxanthines is associated with breast lumps and cysts. Women who have ceased consuming methylxanthine-containing foods have experienced a reversal of this condition.