Caffeinated energy drinks are popular, but they can make your blood vessels less effective, a small study suggests.
These drinks – sold as Monster and Red Bull, to name two – have been linked to cardiovascular, nerve and stomach problems, researchers say.
"A lot of young children use energy drinks when they exercise, a time when you need your artery function to be at the top," said lead researcher Dr John Higgins. He is a professor of medicine at McGovern Medical School at the University of Texas Health Science Center in Houston.
Exercise and sports require maximum blood flow so that oxygen can come to cells quickly, Higgins said. Energy drinks that reduce the diameter of the vessel actually limit the blood flow and oxygen charge, he explained.
"There is more work for the heart and less oxygen supply for the heart. It can explain why there have been cases where children have had a heartbeat after an energy pressure," he said.
In addition, people often chase energy drinks so that they get full effect in a shot, and it can be dangerous, Higgins said.
"These drinks are not intended for children," Higgins warned. In addition, people under the age of 18, women who are pregnant or breastfeeding, caffeine-sensitive individuals, those taking stimulants or caffeine-based drugs or those with heart disease should stay away from energy drinks, he added.
No proven utility
The study included 44 healthy non-smokers medical students in the 20's. The researchers tested the effect of a 710 ml energy pressure on cells that feed blood vessels called endothelial cells.
The function of these cells was tested before and after the participants consumed energy pressure and again 90 minutes later. The researchers looked at blood flow-induced blood flow expansion – an ultrasound measurement that indicates the overall blood vessel's health.
After 90 minutes, the internal diameter of the blood vessels tested was dramatically less on average than before, the investigators found.
This negative effect on blood vessels may be related to ingredients in energy pressure, such as caffeine, taurine, sugar and other herbs, the researchers suggested. Taurin is an amino acid stretched as increasing energy and was originally extracted from the yeasts, hence the name Red Bull, the researchers said.
According to Dr. David Katz, Head of Yale University's Yale-Griffin Prevention Research Center, endothelial function is generally a potent indicator of cardiovascular risk.
However, Katz said, "This is a small study that only looks at acute effects and can not be considered as proof that energy drinks damage the cardiovascular system over time."
That said, the combination of sugar and stimulants in these drinks has no proven benefit, Katz added.
"There are much better ways to increase energy, such as setting up and getting some exercise," he suggested. "In the absence of a reliable benefit, a low level of risk is also offensive."
"Drinks are safe"
A spokesman for a lobby group representing many energy drink manufacturers said the drinks were safe.
"Common energy drinks contain about half of caffeine from a similar large cup of coffee house coffee and have extensive studies and been confirmed safe for the consumption of government agencies around the world," said William Dermody, spokesman for the American Beverage Association. "Nothing in this preliminary investigation counteracts this well-established fact."
The results of the study are scheduled for presentation on November 12 at a meeting of the American Heart Association, in Chicago.
Research presented at meetings is typically considered preliminary until it is published in a peer-reviewed journal.