Scientists test what one can of an
energy drink does to the human body
Downing an energy drink might seem like the perfect motivational aid before a trip to the gym. But a team
of researchers has now tested the effects on the body of Rockstar brand drinks, and the results were not
good for the heart.
The team from the Mayo Clinic in Rochester, Minnesota, said that in just 30 minutes, one can of Rockstar
boosted blood pressure and caused a big jump in levels of fight-or-flight type of hormone. The increase
affects the cardiovascular system, which is made up of the heart and blood vessels.
What's In That Can?
Scientists worked with 25 volunteers, 14 men
and 11 women. Each participant drank a 16ounce can of Rockstar on an empty stomach in
under five minutes. One drink contains 240
milligrams of caffeine, the ingredient in coffee
and cola drinks that leads people to feel more
awake. Rockstar also contains 2,000 milligrams
of an amino acid called taurine, Guarana seed,
ginseng root and milk thistle.
Taurine is an amino acid that helps regulate the level of water and minerals in the blood. Some studies
say it improves mental and athletic performance. Guarana is made from the seeds of a South American
tree and is high in caffeine. Ginseng root is believed to provide energy and lower blood sugar, and milk
thistle has a few uses including also lowering cholesterol.
Rockstar Vs. Placebo
Another day, the same group of people drank a placebo energy drink that tasted just like Rockstar.
However, it had none of the caffeine, taurine or other stimulants. The volunteers did not know which drink
that they were given.
All of the participants were healthy. They each were around 29 years old and had body mass indexes
(BMIs) of about 25, on the border of normal weight and overweight. BMI is a measure of body fat based
on weight and height. None of the volunteers were on medications, and none had consumed alcohol or
caffeine in the day before each test.
Before drinking, researchers measured participants' heart rates and blood pressure, and took blood
samples. All of the tests were repeated 30 minutes later. Just like the volunteers, the researchers
conducting the tests did not know who got the real Rockstar drink and who got the placebo
Blood Pressure Rising
Before the drinks, all volunteers had normal heart rates and blood pressure readings. After drinking
Rockstar, blood pressure readings increased.
Blood pressure is measured in two readings. Systolic blood pressure measures the force created in
arteries when the heart beats. Diastolic blood pressure measures the same thing, but between heartbeats.
People with high blood pressure have a greater chance of developing heart disease.
Systolic blood pressure in those who drank Rockstar rose an average of 6.2 percent, and diastolic blood
pressure rose an average of 6.8 percent. The placebo drinkers were better off with systolic blood pressure
rising just 3.1 percent. There was no change at all in diastolic blood pressure.
Blood Pumping, Heart Pounding
Both drinks caused participants' hearts to beat faster. Rockstar drinkers averaged 3 additional beats per
minute. Those given the placebo averaged about 4 more beats per minute. Doctors said the difference
between the two is unimportant.
The biggest difference was in blood levels of norepinephrine, the hormone that can lead to the so-called
fight-or-flight response. Norepinephrine narrows blood vessels and increases blood pressure and blood
sugar levels. The hormone gets blood pumping and the heart pounding. It mobilizes the brain and body for
action, and is related to adrenaline. When it reaches much higher levels during situations of stress or
danger, it leads to the fight-or-flight response. That reaction causes humans or animals to prepare for
fighting or fleeing.
After consuming Rockstar, the average amount of norepinephrine rose 74 percent in the blood. There was
only a 31 percent increase in the hormone for those who drank the placebo.
Focus On Heart Health
To see whether stressful situations would affect how the energy drink works, researchers asked the group
to answer math questions, squeeze a hand grip or put a hand in ice water for two minutes. None of the
activities made a difference.
Stress may not make a difference, but scientists are still worried about the increases in blood pressure
and norepinephrine. They recently published a study in the Journal of the American Medical Association, a
magazine for scientists. The study found that the increases in blood pressure and hormone after
consuming Rockstar could make people more likely to develop heart disease.
They also said that results might be different with another energy drink or a larger group of volunteers.