Most gymgoers assume sports supplements are “clean”—that what’s listed on the label is exactly what’s in the tub, and that the companies behind them are run by moral folks who care about your health, fitness, and safety.
But that’s often not the case.
Research shows that products frequently contain ingredients not disclosed on the label. Take, for example, a 2025 study published in the journal Drug Testing and Analysis.
Researchers purchased 200 sports supplements from popular online retailers and tested each for substances banned by the World Anti Doping Agency (WADA).
WADA defines a banned substance as anything that meets at least two of the following three criteria: it enhances performance (or could), poses a health risk, or violates the spirit of sport.
The results showed that 35% of the products contained at least one banned ingredient. Worse still, almost 60% of those didn’t list the banned substance on their label or website.
That means athletes—or anyone subject to drug testing—could fail a test simply by taking an off-the-shelf pre-workout or fat burner. And even if you’re not a tested athlete, you’re still ingesting compounds you didn’t knowingly choose to consume—some of which may be illegal or harmful.
The tainted products weren’t always from shady overseas brands—around a third came from the US. Interestingly, however, supplements without an origin label had the highest contamination rate—around 70%.
Muscle builders (53% contamination rate), fat burners (49%), and nootropics (40%) were the worst offenders, followed by pre-workouts (34%).
One product marketed as a “muscle builder” (think testosterone boosters and the like) contained trace amounts of ostarine—a SARM—as well as 1,4-dimethylpentylamine, a banned stimulant that isn’t legal to sell, supply, or use in many countries.
In some cases, the contamination seemed deliberate. Two products contained “overloaded” levels of synthetic stimulants—far beyond what you’d expect from accidental cross-contamination.
One was a BCAA powder that tested positive for high levels of β-methylphenethylamine (βMePEA), a stimulant structurally similar to amphetamine. It also contained small amounts of dextroamphetamine—a controlled substance used to treat ADHD—and phenpromethamine, a methamphetamine isomer.
The other product—a fat burner—contained high levels of phenpromethamine, multiple plant-based stimulants, and trace amounts of mephentermine—a cardiac drug used to treat heart failure.
Creatine (0%) and protein powders (7%), on the other hand, were much “cleaner.”
So, which supplements can you trust?
Start by choosing those that are third-party tested—ideally by labs accredited to international standards. That’s the only reliable way to know a product contains what it claims and nothing it shouldn’t.
Avoid products that hide dosages behind “proprietary blends,” and prioritize those made in reputable, certified facilities.
For a brand that meets all these criteria, try Legion.
Every one of our supplements is tested for purity and potency in an ISO 17025-accredited lab, has a 100% transparent label with no proprietary blends, and is made in NSF-certified, FDA-inspected, cGMP-compliant facilities.
You deserve to know exactly what you’re putting in your body. Many supplement companies won’t give you that peace of mind. We do.
Want to know exactly which supplements you should take to reach your fitness goals? Take our free 60-second quiz and find out now.
