Health and Living

Turns out that extra-tall latte first thing in the morning does more than just perk you up - it also stresses you out.

And even if you consume your caffeine before 1 p.m., you could still be feeling the effects - higher blood pressure and stress levels - by the time you go to bed.

Researchers at Duke University in Durham, N.C., studied the effects of caffeine on 47 regular coffee drinkers.

Participants consumed the caffeine equivalent of four small cups of coffee in two pills (500 milligrams), one pill in the morning and one sometime before 1 p.m.

On another day, participants were given placebos.

When consuming the caffeine pills, participants felt more stressed, had slightly higher blood pressure and produced 32 percent more of the stress hormone epinephrine than when taking the placebo.

Researchers suggest that people who have conditions that are aggravated by stress, such as heart disease or high blood pressure, reduce the amount of caffeine they consume.

FACT: Caffeine has a half-life of an average of four hours, so it will take your body four hours to rid itself of half the amount of caffeine that you've consumed. After eight hours, your body will contain one-quarter of the original amount and, after 12 hours, your body will still contain one-eighth of what you first drank.

Source: Psychosomatic Medicine, 2002: 64, 593-603

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