14 DAY TRIAL // Energy drinks are advertised as if they were the ones pulling the weights when you go to the gym. Some of their chemicals can even induce the contrary effect of what you really want. And a new research presented at the American Heart Association's Scientific Sessions 2007 and carried at the Wayne State University showed that blood pressure and heart rate spurred in healthy adults drinking two cans of a popular mark of energy drink daily.
"While the increases didn't reach dangerous levels in the healthy volunteers, the increases in blood pressure and heart rate could prove to be clinically significant in patients with heart disease or in those who consume energy drinks often. Individuals with high blood pressure and heart disease should be advised to avoid these drinks," said lead author Dr. James Kalus, senior manager of Patient Care Services at Henry Ford Hospital in Detroit, Mich., and a former Wayne State researcher.
Energy drinks are based on caffeine and taurine, an amino acid encountered in low amounts also in meat and fish. Both chemicals are known to boost activity level and alertness but also heart activity and blood pressure, while "sports drinks" comprise just water, sugars and salts.
The 15 healthy young adult subjects (8 of them women and with an average age of 26) had to abstain from ingesting caffeine (from coffee or other sources) for two days before and throughout the tests. On the first day their blood pressure, heart rate and electrocardiogram (ECG) were determined.
The subjects received two cans of an energy drink daily, meaning 80 milligrams of caffeine and 1,000 mg of taurine. Blood pressure, heart rate and ECG were then determined at 30 minutes, 1, 2, 3 and 4 hours after consumption. This was made for 7 days.
4 hours following the drinking of the energy beverage, top systolic blood pressure (when the heart contracts to send blood to the organism) raised by 7.9 % on the first day and 9.6 % on day seven; diastolic blood pressure (when the heart muscle relaxes between contractions) raised by 7 % and respectively 7.8 %, 2 hours following the drinking. Heart rate went up by 7.8 % on day one and 11 % on the seventh day.
During the one week trial, heart rate raised with 5-7 beats per minute and systolic blood pressure by 10 millimeters of mercury (mmHg), while changes in ECG were minor.
"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. While energy drinks increase concentration and wakefulness, people with risk factors for heart disease could have a bad reaction. The subjects in this study were healthy with low blood pressure." said Kalus.
This energy drink comprised as much caffeine as 1-2 cups of coffee and this coffee level should lose effect on blood pressure over 2-3 days of regular consumption.
"Some of the other energy drinks contain much higher levels of caffeine. Thousands of young adults are using these drinks. Some are mixing the energy drinks with alcohol. We don't necessarily know how much they are drinking at a time or whether they are drinking before exerting themselves playing basketball or dancing. Some of the marketing for energy drinks is combined with extreme sports," said Kalus.
"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. People with high blood pressure or heart disease should avoid energy drinks because they could affect their blood pressure and may even alter the effectiveness of their medications," he added.