Downing a 16-ounce Rockstar probably won’t hurt most athletes. In fact, it’ll likely improve performance. But if you’ve been reading headlines lately, you’d think imbibing would send you straight to an early grave.
The source of this misunderstanding is a study published last month in The Journal of the American Medical Association. Researchers from the Mayo Clinic in Rochester, Minnesota, examined the cardiovascular response in 25 healthy people to drinking a 16-ounce can of Rockstar containing 240 milligrams of caffeine: blood pressure and norepinephrine levels increased. The researchers concluded that these effects could increase cardiovascular risk, and the headlines touting energy drinks as scary were written.
“It’s totally sensationalism, and I am the world’s biggest non-advocate of energy drinks,” says Dr. Mark Tarnopolsky, a professor at Ontario’s McMaster University Medical Center and one of the world’s foremost experts on caffeine’s effects on the body, particularly in endurance athletes. Make no mistake, he says, this is a caffeine study cloaked in the hot topic of energy drinks. “There’s no biological effect, or rise in your blood pressure” attributable to the taurine, guarana, ginseng, and other Rockstar additives, Tarnopolsky says. “It’s the caffeine that’s doing it. The study of caffeine is what’s going on.”
Researchers 35 years ago did a more thorough job examining caffeine’s effects in the general population because they addressed whether or not their subjects were habitual caffeine consumers. And that matters a lot, Tarnopolsky says. “It was clearly shown in a study published in 1981 that if you take 250 milligrams of caffeine daily, anywhere between day one to day four, the increase in norepinephrine and the increase in blood pressure completely go away.” Because the body gets used to the cardiovascular effects.
In other words, people who never drink caffeine will likely experience a jump in blood pressure and norepinephrine after drinking a 16-ounce can of Rockstar with 240 milligrams of caffeine. But if they continued to drink 240 milligrams of caffeine daily, by day four, their blood pressure and norepinephrine shouldn’t spike.
That doesn’t mean it’s cool to develop a Rockstar-a-day habit. Tarnopolsky says it’s inappropriate to market the drinks to sedentary people and children, but not because of potential adverse cardiovascular effects. Rather, caffeine can decrease insulin sensitivity. Coupled with energy drinks’ high sugar content, that could contribute to the development of diabetes in those populations.
“It’s a whole different kettle of fish with athletes where caffeine has been shown to increase performance.” Tarnopolsky says. Two-hundred and fifty milligrams of caffeine is comfortably within proven performance-enhancing range for most athletes, or 1 to 6 milligrams per kilogram of bodyweight. And athletes may incinerate the 62 grams—that’s almost 15 teaspoons—of sugar during a tough competition or workout. (Though Rockstar does make a sugar-free drink.)
Additionally, norepinephrine, generally known as the stress or “fight or flight” hormone, can go up three to 400 percent from baseline when you exercise, Tarnopolsky says. In that context, the approximately 40 percent increase in norepinephrine the Mayo Clinic researchers associated with Rockstar isn’t much in an exercising athlete. In fact, that small external norepinephrine boost “may be part of the reason caffeine has an ergogenic benefit,” Tarnopolsky says, as the hormone is thought to increase focus and alertness.
Still, if you want the ergogenic effects of caffeine, Tarnopolsky would rather you get your fix from coffee rather than an energy drink. “Caffeine added as a supplement to energy drinks, [or soda] increases your insulin resistance,” he says. But caffeinated coffee can lower your risk of diabetes. “Mother Nature was smart and put in other substances in coffee that counteract the deleterious effects of caffeine.”