Just One Energy Drink Reduces Endothelial Function

November 15, 2018

CHICAGO — Consuming just one energy drink was associated with acute, significant impairment in endothelial function of young, healthy adults in findings from a new study.

"Our study provides further evidence of potential harms with energy drinks," lead author John Higgins, MD, McGovern Medical School at UTHealth in Houston, Texas, told Medscape Medical News.

"We found an approximately 50% reduction in the arteries' ability to dilate," Higgins said. "Our subjects weren't doing any physical activity, but many people consume energy drinks before they exercise and during exercise, and it is critical that arteries dilate properly to deliver the increased demands of oxygen to the brain, heart, and muscles."

Higgins presented the study at the American Heart Association (AHA) Scientific Sessions 2018.

The study included 44 healthy nonsmoking young medical students (average age, 24.7 years; average body mass index, 23.4). The participants' blood pressure and pulse were checked, and an electrocardiogram was taken.

Participants then underwent baseline testing of endothelial function using endothelium-dependent flow-mediated dilatation with high-resolution ultrasound. The participants then drank an energy drink (24-oz Monster Energy Drink), and measurements were repeated 90 minutes later.

Results showed that energy drink consumption resulted in a significantly attenuated peak flow–mediated dilatation response. The response was reduced from 5.1% at baseline to 2.8% 90 minutes after consuming the energy drink.

Heart rate and blood pressure also increased. Pulse increased by an average of 12 beats per minute, and blood pressure increased by 12-14 mmHg after 5 minutes. By 90 minutes, these values had returned to normal, although endothelial function was still very much reduced.

"This shows that energy drinks are having a direct effect on the endothelium," Higgins said.

"Previous studies have shown adverse effects on blood pressure, pulse rate, and endothelial function, and there are many anecdotal reports of energy drinks being linked to serious cardiovascular and neurological events, including cardiac arrest, especially in young people doing a strenuous physical activity," Higgins noted.

"We used a flow-mediated dilation, which is a very sensitive 'gold standard' measure of vascular function. We also focused on a younger population than included in most previous studies and showed that endothelial function is severely reduced even in these young and healthy individuals after just one energy drink," he said.

"Other studies also being presented at the AHA meeting show that energy drinks are associated with higher platelet aggregation and effects on the nervous system," he noted.

Higgins explained that energy drinks generally contain three key ingredients — caffeine, sugar, and a propriety energy mix that can include amino acids such as taurine, glucose precursors, and vitamins, all often at very high doses.

"We believe the combination of these ingredients can be harmful. We don't even know exactly what is in some of these proprietary energy mixes, and that needs to change. More transparency is clearly necessary," Higgins said.

He also pointed out that because energy drinks are considered to be herbal products or supplements, they are subject to minimal regulation.

"They can be marketed without the stringent safety requirements from the FDA required of drugs. They even have fewer regulations than normal drinks which are classed as beverages," he said. "Bizarrely, a can of cola has a much higher level of regulation than an energy drink. These energy drinks need to be regulated like drugs and go through extensive safety and efficacy studies."

Higgins said certain groups seem to be particularly at risk for adverse effects from energy drinks.

"These include children, people who are caffeine naive or caffeine sensitive, pregnant women, and those with certain medical conditions taking certain drugs such as stimulants — children who take drugs like Ritalin [methylphenidate hydrochloride], for example.

"These drinks are becoming more and more popular, especially with young people. We need to determine what if any amount is safe and how this may differ in different groups," he said.

The marketing of these drinks to young people has to stop, he added. The message should be spread that they can be especially harmful before strenuous exercise, he said. "Sales of energy drinks to children should be prohibited, and the label should clearly state the possible adverse effects and the groups at higher risk."

Higgins believes that mixing these energy drinks with alcohol, which is a common practice among young people when socializing, is especially concerning.

"The mixture of stimulants and depressants is dangerous. People think they are alert so may attempt an extreme physical act like jumping from a height, but the alcohol affects the body's ability to respond appropriately," he noted.

Sachin Shah, PharmD, David Grant Medical Center on Travis Air Force Base and University of the Pacific in Stockton, California, who has done some work in this field, commented on the study for Medscape Medical News.

"This study by Higgins et al builds on previous work by their group and others," Shah said.

Flow-mediated dilation is an important endpoint because it indicates the general health of the vessel, he noted.

"Their work suggests looking at the connection between long-term energy drinks consumption and endothelial dysfunction would be valuable," he said.

American Heart Association (AHA) Scientific Sessions 2018. Abstract Mo1189, presented November 12, 2018.

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