Coffee and Health: Long-term effects

Some potentially harmful effects of coffee are recognized, particularly for people who should take few or no stimulants. Beyond this however, scientific studies of the effects of caffeine have in general failed to prove negative effects, although some have produced contradictory conclusions. An individual study may produce interesting results which may suggest fruitful directions for further research, but usually it is only when several independent studies confirm one another, and any contradictory results can be accounted for, that one can have reasonable confidence in the safety of a drug — particularly an “optional” one like coffee.

Although caffeine does not fall into the class of “addictive” drugs, it may be habit-forming. Some people may experience headache, fatigue, irritability and nervousness when their daily intake of caffeine is quickly and substantially altered.

Moderate caffeine consumption during pregnancy is generally considered safe. A study has not found any effect on low birth-weight or incidence of premature births. However, although it has been suggested that caffeine may stimulate milk production, cautious mothers may prefer to avoid such beverages during pregnancy or while breastfeeding.

Furthermore, a large study has not shown any connection of coffee or tea consumption with breast-cancer incidence. Osteoporosis is another condition which particularly affects women. Previous studies have suggested caffeine consumption as a risk-factor, but a recent analysis concludes that such an effect is probably not significant except in conditions of calcium-deficiency, which can be easily corrected.