Morning caffeine consumption can lead to increases in blood pressure, feelings of stress, and elevated stress hormone levels throughout the day and into the evening hours, according to researchers at Duke University.

The doctors studied 47 healthy, nonsmoking persons who were habitual coffee drinkers. For the study, participants were given a pill containing 500 mg of caffeine (equivalent to approximately four cups of coffee) or a placebo tablet at the beginning of a workday. On a separate workday, those who initially received the caffeine were given placebo, and vice versa. The subjects never knew whether they had received caffeine or placebo on a given day.

Researchers measured blood pressure and heart rate throughout the work day. In the evening, urinary levels of stress-related hormones such as cortisol and epinephrine were measured. The study results, published in the July/August 2002 issue of Psychosomatic Medicine, revealed that those persons who consumed caffeine had a slight but significant increase in their blood pressure throughout the workday and a 32% increase in the level of excreted free epinephrine during the day and evening. Caffeine also potentates the increases in blood pressure and heart rate that were associated with high levels of self-reported stress during the workday. The effects of caffeine persisted into the evening hours until bedtime.

These findings indicate that the effects of morning coffee consumption can exaggerate the body’s stress responses and increase stress hormone levels all day long and into the evening, even when no further caffeine is consumed in the afternoon. Persons who suffer from stress-related diseases or conditions worsened by stress, such as cardiovascular disease and psychological conditions such as anxiety disorders, could be adversely affected by caffeine intake.

If you think caffeine consumption may be causing stress or aggravating your medical condition, remember that experts advise against sudden discontinuation of caffeine intake. Rather, you should decrease the amount of caffeine each day over a period of days and determine if your symptoms and mood improve.

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Cortisol: A steroid hormone secreted by the outer portion, or cortex, of the adrenal glands. Any type of physical or mental stress can increase the production and release of cortisol, and this hormone is often called the “stress hormone” due to its increased secretion during stress responses in the body. Cortisol has a strong anti-inflammatory effect, and it increases mobilization of amino acids from muscle (increasing protein breakdown), increases mobilization of fatty acids (increasing lipid concentrations in the blood), and increases blood glucose concentration.
Also known as: hydrocortisone

Epinephrine: A hormone, secreted by the medulla (inner portion) of the adrenal gland, which (together with norepinephrine) brings about the changes in the body known as the “fight or flight” reaction (or “stress reaction"). Some of the actions of this hormone on various bodily systems include increased metabolism, increased blood pressure, increased mental activity, increased blood flow to the muscles, and increased heart rate. These reactions prepare the individual to deal with perceived threats or stress by enhancing capabilities to fight or to flee.
Also known as: adrenaline

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