The caffeine in coffee is a mild stimulant that increases the activity of the central nervous system. Caffeine helps the drinker to stay alert and enhances mental focus.
Studies suggest caffeine taken on hour before exercise can enhance performance and make the effort seem easier.
As early as 1974, a twelve year study as part of the Framingham Heart Study concluded that there was no association between coffee and heart attacks, coronary heart disease, angina pectoris or sudden death.
Despite evidence from clinical trials that caffeine in coffee can increase blood pressure, most prospective cohort studies have no found moderate coffee consumption to be associated with increased risk of cardiovascular disease.
However caffeine use has been shown to cause anxiety, heart palpitations, trembling, nervousness and facial flushing. These adverse effects are usually dose-related: more side effects were reported when subjects consumed greater than 6 to 9 mg/kg body weight.
Two or three cups of coffee provide about 5 mg/kg body weight of caffeine.
Caffeine in coffee
