Scientists have spotted four stimulants in dietary supplements that shouldn’t be there — including two that have been explicitly banned by the Food and Drug Administration. The findings provide yet more evidence that the minimal regulation of the supplement industry could put consumers at risk.

By testing the contents of six sport and weight-loss supplements bought online, researchers led by Pieter Cohen at Harvard Medical School found four different stimulants among their ingredients, STAT News reports. Two of the stimulants, which are illegal to put in supplements, have nevertheless cropped up in them before. The other compounds were originally investigated as potential drugs, according to the study published Wednesday in the journal Clinical Toxicology. But instead of taking these pills and powders with a doctor’s supervision, people can just buy them online — with potentially dangerous consequences.

That’s because the FDA regulates dietary supplements as food, not drugs, which means the multibillion-dollar supplement industry doesn’t actually have to prove that products are safe or effective. As long as an ingredient was part of the food supply before 1994, or the manufacturer has filed the right paperwork showing that a new dietary ingredient “will reasonably be expected to be safe,” it can legally go into a supplement. But the FDA doesn’t generally vet products before they hit the shelves, so drugs like Viagra, stimulants, laxatives, even muscle relaxants have slipped past them and into consumers’ hands, Vox reports.

In fact, scientists with the Centers for Disease Control and Prevention estimate that dietary supplements cause more than 23,000 emergency room visits every year. “People just aren’t on alert when they’re considering dietary supplements because they assume they’re safe,” says Amy Eichner, a scientist with the US Anti-Doping Agency (USADA) who wasn’t involved in the study. It’s important work, she says, but “it’s a sad day that we have to keep coming back to this.”

This latest investigation started when military personnel began asking about new ingredients on dietary supplement labels: things with names like DMHA, 2-amino-6-methylheptane, or Aconitum kusnezoffii — a toxic plant in the monkshood family. That got the attention of Patricia Deuster, director for the Consortium for Health and Military Performance at the Uniformed Services University. She teamed up with Harvard’s Pieter Cohen, who’s spent his career sniffing out hidden, illegal, and risky ingredients in supplements. But he hadn’t seen these ingredients before. “We really didn’t have a sense of what was behind them,” Cohen says. “Is this a new drug? Was this the old stimulants that are masquerading as a new ingredient?”

To find out, the researchers shopped online for supplements containing the suspect ingredients, and sent six different pills and powders off to be tested at two different laboratories. They were looking for stimulants related to 1,3-dimethylamylamine (1,3-DMAA), which is explicitly banned by the FDA because it’s been associated with heart attacks and even deaths — including of two military personnel. Less is known about its chemical relative, DMBA, which is also banned and may increase heart rate and blood pressure, the US Anti-Doping Agency says.

The researchers report finding both of the banned stimulants: 1,3-DMAA in Gold Star’s Infrared and 1,3-DMBA in a product sold by Chaos and Pain called Cannibal Ferox AMPed. Gold Star did not respond to requests for comment, and Wayne Banks, owner of Chaos and Pain, declined to comment.

The team also found two stimulants known in the scientific literature that hadn’t been seen before in supplements: 1,4-DMAA, which was studied in cats and dogs in the 1940s and ‘50s, and octodrine, a stimulant drug that has been prescribed in Europe in pill form to treat conditions like asthma. (The FDA has only approved octodrine inhalers, the study says.)

The researchers detected more than double the dose of octodrine doctors prescribed in just one serving of a supplement called Game Day, sold by Man Sports. (Man Sports’ Steven Salmon declined to comment on the record.) The team also found 1,4-DMAA in three different products, the study reports: another Chaos and Pain product called 2-Aminoisoheptane, another Gold Star product called Triple X, and Bee Fit with Trish’s Simply Skinny Pollen, where it was combined with the banned stimulant 1,3-DMAA. Bee Fit with Trish also did not respond to requests for comment.

Cohen alerted the FDA to his team’s findings in June, but says he hasn’t seen any results yet. The FDA responded that there are many hoops to jump through before they can take action against a product. These include documenting its movement across state lines, identifying suspicious ingredients, and determining whether those ingredients break the law. And they have to do this for each new ingredient, says FDA spokesperson Theresa Eisenman — no matter how similar it is to the last suspicious ingredient that came on the market. “It’s just a constant game of whack-a-mole,” says USADA’s Eichner.

This slow process isn’t doing consumers any favors, and this latest study makes one thing especially clear, says Joshua Sharfstein, a professor at Johns Hopkins University and former FDA deputy commissioner: “Buyers should beware of weight-loss and bodybuilding supplements,” he said in an email to The Verge. “The current approach to regulatory oversight is inadequate to protect consumers.”