Have we become a nation of energy-boosting addicts? Sure, most of us drink caffeinated coffee to get a little boost, but now we’re spending more than $12.5 billion a year on energy drinks, shots, and drink mixes—60 percent more than we spent in 2008. No wonder energy drink makers are so eager to keep their products on shelves despite facing wrongful death lawsuits and harsh warning letters from federal health officials, members of Congress, and consumer watchdog groups.

The US Food and Drug Administration issued a harsh warning on Thursday against energy drinks and supplements containing dimethylamylamine (DMAA) telling consumers to stay away from it while adding that the agency was “using all available tools at its disposal” to ensure that it’s no longer sold on the marketplace.

Emergency room visits related to energy drinks doubled from 10,000 to 20,000 visits between 2007 and 2011, often due to heart problems linked to a caffeine overdose. Those at biggest risk? Teens and young adults who are the targets of marketing efforts by energy drink makers, according to a federal investigation released on Wednesday by Massachusetts Congressman Edward Markey and two US senators.

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“It’s time for energy drink makers to stop masking their ingredients, stop marketing to kids, and start being more transparent with their products,” Markey, a candidate for the Senate, said in a statement. “It’s time for the FDA to crack down on these drink makers and for the FTC to investigate advertising practices of these companies to ensure that kids and parents are not being subjected to deceptive marketing practices.”

More than one-third of teens consume energy drinks, according to the American Academy of Pediatrics, which recently warned pediatricians to urge their patients not to use these products because they contain unknown and unregulated amounts of caffeine and other stimulants that raise the risk of heart palpitations, insomnia, and dehydration.

The congressional report found that energy drink manufacturers determine on their own whether to call their drinks beverages or dietary supplements, which have different sets of rules for what can be added and what must be disclosed on the label. Energy drink beverages can’t include any ingredients that aren’t “generally recognized as safe” for foods by the US Food and Drug Administration; beverage manufacturers don’t need to disclose how much caffeine their drinks contain, nor file a report with the FDA if someone has a serious side effect from their products.

Energy drink supplements, on the other hand, have a different label that must list the amount of caffeine—unless it’s in a mix of proprietary ingredients; they can also contain a wide range of other ingredients such as herbs and amino acids without proving that they’re safe, as long as they were used in supplements before a 1994 federal supplement law was enacted.

Unlike beverage makers, supplement manufacturers must alert the FDA if they receive reports of side effects from their product.

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It’s ridiculously confusing and the FDA has been trying for four years to clearly demarcate the line between energy beverages and liquid energy dietary supplements. Agency officials still haven’t come up with a solution.

In the meantime, consumers have filed wrongful death lawsuits on behalf of loved ones who died after consuming energy boosters. A lawsuit was filed last October against the maker of Monster Energy Drink (a beverage) by the parents of a 14-year-old Maryland girl who went into cardiac arrest after drinking two of the 24-ounce Monster Beverage Corp. drinks.

Another lawsuit was filed in February by the parents of Michael Sparling, one of two soldiers who died in 2011 after using the energy drink mix Jack3d (a supplement); it contains caffeine and a stimulant called DMAA that is purported to boost workout performance.

Monster said in previous statements to the media that it doesn’t believe its beverages are responsible for the girl’s death and will vigorously fight the lawsuit. USPlabs, the manufacturer of Jack3d, declined to comment on the lawsuit.

In its warning on DMAA, the FDA said it had received 60 reports of serious conditions such as heart attacks, seizures, psychiatric problems, and deaths that were associated with DMAA use. “FDA has warned companies known to be using DMAA in dietary supplements that those products containing this ingredient are illegal.” That’s because the agency considers it a new dietary supplement that needs to be tested for safety before it can be approved as an additive in products.

USPlabs spokesperson Kerri Toloczko told me in an e-mailed response to my questions that Jack3d is “among the most studied finished dietary supplements ever sold” and sent me a summary of five manufacturer-funded safety studies looking at the effects of DMAA and caffeine on blood pressure, heart rate, and kidney and liver function while people exercised. According to the summary, none of the studies found any adverse effects. The studies were small, though, with none containing more than 50 participants.

Clinical studies of new drugs typically have thousands of participants to determine efficacy and safety risks.

In its response letter to the FDA, USPlabs insisted DMAA was a natural dietary ingredient found in the geranium plant, proven safe through hundreds of years of use in tea infusions and previous studies of geranium oil. But the FDA said it has found the information provided by the company to be “insufficient to defend the use of DMAA as an ingredient in dietary supplements.”

What’s more, some public health researchers say there are negligible, if any, amounts of DMAA in geranium plants. “Companies made a new pharmaceutical and are trying to sell it in the guise of a plant extract,” said Dr. Pieter Cohen, an internist at the Cambridge Health Alliance and assistant professor at Harvard Medical School. He compared DMAA to an amphetamine and called for a ban on it last year in a research letter published in the Archives of Internal Medicine.

“Patients tell me it pumps them up, gets them to work out better, maybe lose a little weight,” Cohen said. “But they get addicted to the caffeine and other stimulants and get headaches it they stop using it for a day.”

Toloczko wouldn’t tell me whether USPlabs synthesized DMAA or extracted it from geranium plants to make their product, saying that it was “proprietary information.” She also wouldn’t tell me exactly how much DMAA or caffeine the products contained. The proprietary blend listed on the Jack3d label says only that it contains 4,145 milligrams of six different ingredients, including DMAA and caffeine.

“Caffeine is exceedingly safe at low doses, 100 to 300 milligrams a day, which is in a few cups of coffee,” Cohen said. “But when you go above 600 to 1,000 milligrams, you start to have side effects like jitteriness, heart palpitations, and panic attacks, and this could have synergistic effects with stimulants like DMAA, which are also in these supplements.”

The FDA agreed and said it’s “required to undertake what are usually lengthy scientific and legal steps” to ban DMAA from the market, but until that can be accomplished, the agency is “urging consumers to check labels and avoid any dietary supplements containing DMAA.” Here are the 10 possible names that might appear on the label.