Coffee Risks

Many notable effects of coffee are related to its caffeine content.

Many coffee drinkers are familiar with "coffee jitters", a nervous condition that occurs when one has had too much caffeine. Coffee can also increase blood pressure among those with high blood pressure, but follow-up studies showed that coffee still decreased the risk of dying from heart disease in the aggregate. Coffee can also cause insomnia in some, while paradoxically it helps a few sleep more soundly. It can also cause anxiety and irritability, in some with excessive coffee consumption, and some as a withdrawal symptom. There are also gender-specific effects, in some PMS sufferers it increases the symptoms, and it can reduce fertility in women, also it may increase the risk of osteoporosis in postmenopausal women, and there may be risks to a fetus if a pregnant woman drinks 8 or more cups a day (48 U.S. fl oz or 1.4 L or more).

A February 2003 Danish study of 18,478 women linked heavy coffee consumption during pregnancy to significantly increased risk of stillbirths (but no significantly increased risk of infant death in the first year). "The results seem to indicate a threshold effect around four to seven cups per day," the study reported. Those who drank eight or more cups a day (48 U.S. fl oz or 1.4 L) were at 220% increased risk compared with nondrinkers. This study has not yet been repeated, but has caused some doctors to caution against excessive coffee consumption during pregnancy.

Decaffeinated coffee is occasionally regarded as a potential health risk to pregnant women, due to the high incidence of chemical solvents used to extract the caffeine. These concerns have almost no basis, however, as the solvents in question evaporate at 80–90 °C, and coffee beans are decaffeinated before roasting, which occurs at approximately 200 °C. As such, these chemicals, namely trichloroethane and methylene chloride, are present in trace amounts at most, and neither pose a significant threat to unborn children. Women still worried about chemical solvents in decaffeinated coffee should opt for beans which use the Swiss water process, where no chemicals other than water are used, although higher amounts of caffeine remain.

The American Journal of Clinical Nutrition published a study in 2004 which tried to discover why the beneficial and detrimental effects of coffee are conflicting. The study concluded that consumption of coffee is associated with significant elevations in biochemical markers of inflammation. This is a detrimental effect of coffee on the cardiovascular system, which may explain why coffee has so far only been shown to help the heart at levels of four cups (20 fl oz or 600 mL) or fewer per day.

The health risks of decaffeinated coffee have been studied, with varying results. One variable is the type of decaffeination process used; while some involve the use of organic solvents which may leave residual traces, others rely on steam.

A study has shown that cafestol, a substance which is present in boiled coffee drinks, dramatically increases cholesterol levels, especially in women. Filtered coffee only contains trace amounts of cafestol.