Anna Svatikova, M.D., Ph.D., of the Mayo Clinic, Rochester, Minn., and colleagues randomly assigned 25 healthy volunteers (age 18 years or older) to consume a can (480 mL; 16 fl. oz.) of a commercially available energy drink (Rockstar; Rockstar Inc) and placebo drink within 5 minutes, in random order on 2 separate days, maximum 2 weeks apart. The placebo drink, selected to match the nutritional constituents of the energy drink, was similar in taste, texture, and color but lacked caffeine and other stimulants of the energy drink (240 mg of caffeine, 2,000 mg of taurine, and extracts of guarana seed, ginseng root, and milk thistle). This JAMA study is being released to coincide with its presentation at the American Heart Association's Scientific Sessions 2015.
Energy drink consumption has been associated with serious cardiovascular events, possibly related to caffeine and other stimulants. The researchers examined the effect of energy drink consumption on hemodynamic changes, such as blood pressure and heart rate. Participants were fasting and abstained from caffeine and alcohol 24 hours prior to each study day. Serum levels of caffeine, plasma glucose, and norepinephrine (noradrenaline) were measured and blood pressure and heart rate were obtained at baseline and 30 minutes after drink ingestion.
Caffeine levels remained unchanged after the placebo drink, but increased significantly after energy drink consumption. Consumption of the energy drink elicited a 6.2 percent increase in systolic blood pressure; diastolic blood pressure increased by 6.8 percent; average blood pressure increased after consumption of the energy drink by 6.4 percent. There was no significant difference in heart rate increase between the 2 groups. The average norepinephrine level increased from 150 pg/mL to 250 pg/mL after consumption of the energy drink and from 140 pg/mL to 179 pg/mL after placebo (change rate: 74 percent vs 31 percent, respectively).
"These acute hemodynamic and adrenergic changes may predispose to increased cardiovascular risk," the authors write. "Further research in larger studies is needed to assess whether the observed acute changes are likely to increase cardiovascular risk."
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