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Caffeine Keeps Going, and Going...

You're not alone drinking that morning cup of coffee. Around 85% of Americans drink caffeine daily in the form of coffee, tea, or soft drinks. People take caffeine because it is a stimulant - our bodies respond to caffeine essentially the same as they do to stress - but its effects may last longer than you might expect, based on a recent study in Psychosomatic Medicine.

Forty-seven healthy, habitual coffee drinkers were followed for three days to monitor blood pressure, heart rate, and hormonal changes based on caffeine consumption. The individuals were monitored through a normal day of drinking coffee; a day when given caffeine pills twice (total equivalent to four cups of coffee); and a day when only given placebo pills containing no caffeine.

Caffeine significantly raised both diastolic and systolic blood pressures and increased levels of epinephrine (a stress hormone) in the body by 32%, which in turn increased feelings of stress. Also, although all caffeine pills were given prior to 1 p.m., their effects lingered until bedtime.

Even eight hours after caffeine consumption, one-quarter of the amount consumed remains in your body. Stress reactions and higher blood pressure caused by caffeine may be dangerous, so try to limit yourself to one cup of coffee or tea each morning, and avoid caffeine altogether in the afternoon and evening.


Lane JD, Pieper CF, Phillips-Bute BG, et al. Caffeine affects cardiovascular and neuroendocrine activation at work and home. Psychosomatic Medicine 2002:64, pp. 595-603.

Other nutrition studies can be found at