Caffeinated energy drinks, heavily marketed to young people, have exploded in popularity in recent years, with the market growing by triple digits and projected to reach $20 billion in sales next year.
But new questions are being raised about their safety, and the lack of government oversight of these popular beverages.
Reports released last week by the US Food and Drug Administration bring to 13 the number of deaths possibly connected to two popular brands of the drink, Monster Energy and 5-Hour Energy, since 2009. Federal officials had previously linked 7,000 emergency room visits to caffeinated energy drinks between 2004 and 2009.
The reports do not mean that the drinks caused any deaths — just that people drank the beverages before falling ill — and it's unclear at this point what might cause the drinks to be dangerous. But the reports have led critics, including two US senators, to call for federal regulators to take a closer look at the drinks.
"The existence of an adverse event report does not necessarily mean that the product identified in the report actually caused the adverse event," FDA spokeswoman Shelly L. Burgess wrote in an e-mail. "FDA assesses the relationship, if any, between a product or ingredient and the reported adverse event."
A few brands of energy drinks have labels that warn children and pregnant women not to consume them, though the actual risk is unclear, because the safety of the drinks hasn't been carefully studied. Many of the drinks contain high levels of caffeine — though many have less caffeine per ounce than a cup of brewed coffee — as well as sugar and small amounts of ingredients like the amino acid taurine, which may improve athletic performance, and plant extracts guarana and ginseng, which are possible stimulants.
"It's hard to believe that 200 or so milligrams of caffeine could cause deaths, so much more information is needed," said Marion Nestle, a professor in the Department of Nutrition, Food Studies, and Public Health at New York University. "That's why investigations are essential at this point."
Many energy drinks are sold as "dietary supplements," not food, so unlike sodas, they do not come under federal caffeine limitations, although they must report any adverse events related to their products and the government does review claims made on the products' labels.
The FDA is considering several citizen petitions requesting limits on caffeine in foods and requiring that labels state these limits, according to Burgess, a team leader for Food, Veterinary and Cosmetic Products.
It can be challenging to figure out how much caffeine is in energy drinks. In a report in its December issue, Consumer Reports found that 11 of 27 energy drinks tested do not list their caffeine content, and five of the products that did — Arizona Energy, Clif Shot Turbo Energy Gel, Nestlé Jamba, Sambazon Organic Amazon Energy, and Venom Energy — had 20 percent more caffeine than was listed on their label.
People with certain medical problems, such as heart disease, vascular conditions, and panic and seizure disorders, have long been told to limit or avoid caffeine. A 14-year-old girl who died last year after drinking two Monster Energy Drinks within 24 hours had a heart condition that may have made the drinks particularly dangerous for her.
Dr. Richard Church, an assistant professor of emergency medicine and a medical toxicologist at the University of Massachusetts Medical School in Worcester, said he believes that the drinks are generally safe. But he says people need to be smarter about drinking them.
Young people tend to pound back energy drinks, quickly increasing their blood concentrations — and the strength — of caffeine. They also often drink more than one serving, thinking of it like a soda, and not realizing its potency.
"When you drink a cup of coffee, you sip it," Church said. "I don't know of anybody who chugs more than one espresso."
Because body weight also determines concentration, young people are considered more vulnerable to caffeine than adults, said Ted Kallmyer, a biologist and editor of the website Energyfiend.com, which tracks caffeine and calculates lethal doses of the popular chemical. (To consume a fatal amount of caffeine, a 150-pound person would have to drink 64 16 oz. cans of Monster Energy, and a 100-pound person 43 cans, according to the site.)
Obviously, there are also personal variations in how people respond to caffeine, too. Some can drink coffee all day with little effect; others can't sleep at night if they have caffeine after noon.
"What is clear is that [some] people increase their wakefulness by drinking caffeine," said David Elmenhorst, a neuroscientist at the Institute of Neuroscience and Medicine in Jülich, Germany.
A new study also suggests that the drinks may be putting soldiers at risk. Forty-five percent of American service members in combat units in Afghanistan consume energy drinks every day — many drinking them for free in military cafeterias. The 14 percent who drank at least three a day were more likely to sleep under 4 hours per night, report stress-related sleep problems, and fall asleep on guard duty than those who drank less, the study showed.
Experts say it's also possible that other ingredients in caffeinated energy drinks or the combination of those ingredients with caffeine are causing or contributing to the reported health problems.
"You have to look at a product in its totality," said Gerry David, president and CEO of Celsius, another energy drink company. "Things work differently when they're together."
Celsius contains no sugar — though many other energy drinks are loaded with it — and has been shown safe in seven separate studies, David said.
It's possible that the risk increases when energy drinks are mixed with other substances. Combining alcohol with energy drinks has been shown to be dangerous. In 2010, the Food and Drug Administration sent warning letters to four companies that the caffeine added to their alcoholic beverages was unsafe. The companies removed the caffeine and now market their drinks as alcoholic, rather than energy products.
The federal Drug Abuse Warning Network reported last year that 7,301 emergency department visits were connected to caffeinated energy drinks between 2004 and 2009. Of those, 44 percent had alcohol, medications or illegal drugs in their bloodstream in addition to the energy drink..
It's possible that the drinks are only dangerous when consumed a certain way by vulnerable people, said Church, who has energy drinks occasionally when he needs to pull night shifts at the hospital.
"You need to know what you're putting in your body," he said. "It's just about being smart."
Nestle, of NYU, said the problem is we really don't know whether they are dangerous or not, because they haven't been studied.
Still, many people are sticking with their energy drink habits.
Seth Hall, 23, of Smithfield, R.I., said he's not worried about the safety of Monster Energy Drinks, which he's consumed daily since age 11.
The community college student said he likes Monster's sweetness and the extra edge he gets — especially around midterms and finals time.
"It doesn't really work," to improve his grades, he said, "but I try anyway."
Although he's cut down to just two cans a day, he would happily go back to his six-a-day habit — if, at $2.50 per can, he could afford it.
"Money's tight right now," he said.
Karen Weintraub can be reached at Karen@KarenWeintraub.com.