People with high blood pressure or heart disease should not consume energy drinks, advise doctors from Henry Ford Hospital, Detroit.

In a study, Dr. James S. Kalus and colleagues found that healthy adults who drank two cans of a popular energy drink experienced an increase in blood pressure and heart rate.

The increases in blood pressure and heart rate were insignificant for healthy adults, but could prove a problem for people with a heart-related condition, the researchers warn.

Energy drinks, marketed to enhance brain function and stamina, usually contain caffeine, taurine, sugars, vitamins, and other nutritional supplements, the investigators point out. The potential effects of energy drinks on blood pressure and the heart have not been well studied.

To look into this, the researchers studied 15 healthy volunteers, 20 to 39 years old, who abstained from other forms of caffeine for 2 days prior to and throughout the study. On the first day after baseline blood pressure and heart rate measurements were taken, the adults consumed two cans of an energy drink. The researchers then measured the participants' blood pressure and heart rate again at different time points.

Tests showed that the subjects' average heart rate increased 7.8 percent the first day and 11 percent the seventh day. Blood pressure increased at least 7 percent the first and seventh days.

"Increases in blood pressure and heart rate of the magnitude observed in our study could be significant in persons with known cardiovascular disease," Kalus and his associates maintain. Young individuals with undiagnosed, premature cardiovascular disease could also be at risk.

The researchers say consumption of energy drinks - which should not be confused with sports drinks, which aim to replenish carbohydrates and electrolytes that a body needs - "could, theoretically, be a frequently overlooked cause of altered medication effectiveness or even hospital admissions or emergency department visits."

SOURCE: Annals of Pharmacotherapy, April 2009.