Nearly 90 per cent of the world's adult population consumes caffeine daily. Next to water, coffee and tea are the most widely consumed drinks in the world. Children take caffeine mostly in the form of chocolates, ice cream and caffeinated soft drinks. Coffee and tea contain several compounds that may have both beneficial and adverse health effects: caffeine and antioxidants (eg, polyphenols, catechins, and flavonoids). The following is a brief overview of these effects.
Neuropsychiatric effects: As anyone cramming all night for an exam or working a night shift knows, caffeine increases alertness and energy, and improves attention, mood, psychomotor performance, and working memory.
Sixty five mg of caffeine (150 ml of instant coffee) has a modest painkilling effect in tension and migraine headaches. In fact, many OTC medications for migraine contain large doses of caffeine. On the other hand, chronic caffeine consumption may be associated with headache - which is also a symptom of caffeine withdrawal!
Long-term caffeine use has a mild protective effect against Parkinson disease and Alzheimer disease.
Taking more than five cups of coffee/day can cause anxiety, nervousness, insomnia, irritability, and even panic attacks.
Heart effects: Taking up to three cups of coffee per day may protect against myocardial infarction. In susceptible individuals, heavy coffee use can trigger heart rhythm abnormalities and other cardiac disorders. Contrary to popular opinion, caffeine has little or no effect on blood pressure in habitual coffee drinkers, nor does it increase the risk of hypertension.
Endocrine and gastrointestinal effects: Taking coffee or tea reduces the risk of developing type-2 diabetes mellitus. Among alcoholics, caffeine reduces the risk of developing cirrhosis of the liver. Caffeine is a potent stimulator of the intestines and helps prevent constipation.
Cancer: Although population studies suggest that intake of green tea may prevent several cancers, hard evidence from prospective studies is lacking. Randomized studies on caffeinated drinks and cancer are difficult to do because most cancers have a long latency period.
Musculoskeletal effects: In women with low calcium intake, caffeinated drinks increase the risk of osteoporosis. Among athletes, caffeine improves performance across a wide range of physical activities. The International Olympic Committee prohibits urinary caffeine concentrations of more than 12 mcg/ml. To stay within the legal limit, athletes should limit their intake of coffee to two to three cups per day (or the equivalent intake for other forms of caffeine).
(The writer is a specialist in Internal Medicine)