AHA: Energy Drinks Amp Up Blood Pressure


ORLANDO, Nov. 7 -- Energy drinks boost blood pressure in even the young and healthy people and may leave hypertensive adults more charged up than they bargained for, researchers said here.
Action Points
Explain to interested patients that the study suggests that energy drinks may not be recommended for patients with hypertension and other cardiovascular disease.
Note that this study was published as an abstract and presented orally at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed publication.
Consumption of two energy drinks a day increased systolic blood pressure by 10 mm Hg and heart rate by five to seven beats per minute, according to a small study reported at the American Heart Association meeting.
Although this degree of change may hold little danger for most young patients, it likely would be clinically significant with regular consumption or in patients with cardiovascular disease such as hypertension, said James S. Kalus, Pharm.D., of the Henry Ford Medical Center in Detroit, Mich., and colleagues.
"If you know you have cardiovascular disease or are taking medication to lower blood pressure, it is important to avoid energy drinks until we learn more about what they do," he said.
Energy drinks typically contain high levels of caffeine and the amino acid taurine. These compounds have been shown in previous studies to have an impact on cardiac function and hemodynamic status, although the data available for caffeine are controversial, Dr. Kalus said.
The study included 15 healthy volunteers (53% women) with an average age of 25.9 who abstained from caffeine for two days before and during the study.
After participants' blood pressure and heart rate were measured and an electrocardiogram was taken at baseline, they drank two cans of an energy drink containing 80 mg caffeine and 1,000 mg taurine. The same tests were repeated at 30 minutes, and at one, two, three, and four hours after consumption while the volunteers sat around watching movies.
The men and women drank two cans a day for the following five days with another regimen of testing on the last day.
Diastolic blood pressure peaked two hours after administration with a 7% elevation on day one (P=0.046) and 7.8% elevation on day seven (P=0.063). The other measures all peaked at four hours after consumption.
The four-hour changes on days one and seven, respectively, included:
Systolic blood pressure increased by 7.9% (P=0.006) and 9.6% (P0.001).
Heart rate rose by 7.8% (P=0.009) and 11.0% (P0.001)
Corrected QT-interval tended to increase by 4.5% (P=0.368) and 5.5% (P=0.052).
Although some data suggest tolerance can develop to the caffeine in coffee, no blunting of the energy drink effects was seen over the seven days, Dr. Kalus said. However, a week might be too short a period for that to be noticeable, he added.
The brand of energy drink used in the study contained the caffeine equivalent of two cups of coffee, but it's not clear whether the other compounds in it such as sugar and B vitamins contributed to the effect, he said.
Nevertheless, the main compounds implicated in the cardiovascular alterations -- caffeine and taurine -- are consistent ingredients across brands. This suggests the findings are likely generalizable across energy drinks, though not to sports drinks, which typically do not have caffeine, Dr. Kalus said.
The study was supported by the Wayne State Undergraduate Research Fund. Dr. Kalus reported no conflicts of interest.
Primary source: American Heart Association meetingSource reference: Steinke L, et al "'Energy Drink' Consumption Causes Increases in Blood Pressure and Heart Rate" AHA meeting 2007; Abstract 3661.