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Popping an energy drink might get you through the day — but it could also increase your risk of heart problems.

Just one can of Rockstar Energy Drink can cause potentially damaging physiological changes, according to a study published in the Journal of the American Medical Association. Those 16 ounces — packed with sugar, caffeine, and herbal stimulants — induce a flood of norepinephrine, the “fight or flight” hormone, as well a significant spike in blood pressure.

Researchers had a hunch that energy drinks meant trouble, because more and more young adults had been showing up at emergency rooms with acute chest pain, palpitations, and disturbed sleep patterns.


“We don’t usually see these problems in young healthy people,” said Dr. Anna Svatikova, a cardiologist at the Mayo Clinic in Rochester, Minn. “So when young healthy people come to a doctor and have abnormal vital signs, it is impetus to ask about possible energy drink intake.”

The study was small, but its results will likely reinforce long-running concerns about the energy drink industry, which is projected to ring up at least $10 billion in US sales this year.  In 2011, energy drinks were involved in nearly 21,000 visits to American emergency rooms, according to the Drug Abuse Warning Network.


Svatikova and her team wanted to know what was really going on in the cardiovascular system when people drank an energy drink, so they did a small, double-blind study.

On two separate days, 25 young, healthy volunteers were given either punch-flavored Rockstar Energy Drink or a placebo, which looked and tasted exactly like Rockstar but didn’t have most of the stimulants. The researchers tested participants’ blood pressure and norepinephrine levels a half hour before and after the drink. Both drinks caused a jump in both blood pressure and norepinephrine levels — but the spike was much higher after the energy drink than after the placebo.

The results shouldn’t come as a surprise. Like Rockstar, the placebo was packed with sugar, but it didn’t have the ingredients that really cause you to buzz, which include everything from run-of-the-mill caffeine to an extract from guarana, a South American creeping shrub with clusters of red berries. Rockstar also contains an extract of milk thistle, a spiny weed that you can find in your backyard.

The American Beverage Association responded to the study by saying “there is nothing unique about the caffeine in mainstream energy drinks, which is about half that of a similar sized cup of coffeehouse coffee.” The group also said scientific research and regulatory bodies have established the safety of energy drinks.

But the companies behind both Rockstar and Monster energy drinks decided a few years ago to market their products as beverages, instead of dietary supplements, which meant that they no longer had to let federal regulators know if their energy drinks were linked to adverse health affects, the New York Times reported in 2013.

Executives at Rockstar declined to comment beyond the American Beverage Association’s statement.

Svatikova, for her part, said she didn’t mean to single out the company’s products. “We selected one of the top sellers on the market,” she said, noting that ingredients vary from one energy drink to another.

Her sample size may have been small, but “the beauty of it is in the design,” she said. “It’s a clinical trial, randomized, double-blind, placebo controlled.”

This article was originally published on Nov. 8, 2015.