NEW YORK: Energy drinks may help you to exercise but just give a second thought before you down the next bottle -- the beverage can raise your blood pressure as well as heart rate.

Researchers in the United States have carried out a study and found that most energy drinks contain high levels of caffeine and taurine, an amino acid found in meat and fish, which may be harmful especially to those with heart problems, the Science Daily reported on Wednesday.

"Blood pressure and heart rate naturally go up during physical activity. This could be further augmented by energy drinks. Energy drinks could affect some individuals if they didn't know they had a problem in the first place," according to lead researcher Dr James Kalus of the Henry Ford Hospital.

Dr Kalus and his team came to the conclusion after examining 15 healthy young adult participants -- 53 per cent female with an average age of 26 -- who were asked to abstain from other forms of caffeine for two days prior to and throughout the study.

The participants drank two cans of an energy drink, that contained 80 milligrams of caffeine and 1,000 milligrams of taurine, daily over a period of seven days -- their heart rates rose by about eight per cent on the first day and 11 per cent on the seventh day.

In fact, over the duration of the study, heart rates increased five to seven beats per minute and systolic blood pressure increased 10 millimetres of mercury after energy drink consumption, the researchers found.

"This occurred while participants were sitting in chairs watching movies. The increases in heart rate and blood pressure weren't enough for something to happen acutely, but a person on hypertension medication or who has cardiovascular disease may not respond as well," Dr Kalus said.