Caffeine can also have some serious side effects. It is known to raise blood pressure. People with high blood pressure or heart conditions are told by doctors to eliminate caffeine from their diet. Caffeine also causes a flushed face, dieresis, disturbances in stomach and intestines, muscle twitching, rambling flow of thought and speech, periods of inexhaustibility and disturbances in muscular activity. For women, too much caffeine has been linked to infertility.
Pregnant women have an increased chance of miscarrying during pregnancy.
Some studies have also shown a link between drinking coffee and an increased risk of cancer. A cup of coffee contains between 90 and 120 mg of caffeine. A cup of tea yields 40 to 100 mg. Cocoa or cola drinks 20 to 50 mg. The Addiction Research Foundation says people can become dependent on caffeine.