How's this for a jolt: young adults who drink even just one energy drink a day may increase their risk of heart disease.

Studies have linked energy drinks and heart issues before, but those warnings were aimed at people who drank large quantities or combined the drinks with alcohol or drugs. According to new research published in the Journal of American Medical Association, consuming a single 16-ounce drink spikes blood pressure and elevates the body's stress hormone response.

"We now show that the increases in blood pressure are accompanied by increases in norepinephrine, a stress hormone chemical, and this could predispose an increased risk of cardiac events — even in healthy people," the study's lead author, Dr. Anna Svatikova, of the Mayo Clinic, said in a news release.

Loaded with caffeine and sugar, energy drinks are especially popular among teens and young adult men. The amount of caffeine in a single energy drink is the same as three cups of coffee or cans of soda, the Centers for Disease Control and Prevention says, except the energy drinks tend to be consumed much faster than someone might sip multiple cups of coffee.

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