A large portion of sports and dietary supplements may be misleading when it comes to labeling their ingredients, according to a research letter published in JAMA Network this week.

The researchers found that 89% of dietary supplements examined didn’t accurately label the ingredients in the products and up to 12% were made up of ingredients that are prohibited by the Food and Drug Administration.

When it comes to supplement quality and accuracy, there tends to be wide variability because unlike prescription drugs, the supplement industry is one that the FDA doesn’t regulate. As a result, supplement makers don’t have to prove their products’ safety or efficacy, or be held up to the standards of clinical trials.

It’s not surprising, then, that the authors of the recent study found quality issues and misleading labels of sports supplements. 

These products included compounds R vomitoria, methylliberine, halostachine, octopamine and turkesterone. Researchers honed in on those five ingredients in particular because they’re often used in sports supplements to enhance performance and serve as substitutes of sorts for ephedra, an FDA-prohibited stimulant.

“The FDA does not pre-approve these ingredients, or any supplement ingredient, for either efficacy or safety before their introduction, but FDA inspections have found that supplement manufacturers often fail to comply with basic manufacturing standards, such as establishing the identity, purity, or composition of the final product,” the authors wrote.

Among 57 products, 40% didn’t contain a detectable amount of one of those five labeled ingredients, the researchers found. Among the products that did have detectable levels of the labeled ingredient, the actual amount varied from a low of 0.02% to a high of 334%, meaning the products are widely inconsistent.

The researchers also found that 12% of products examined had at least one FDA-prohibited ingredient in them, including synthetic stimulants like oxilofrine, octodrine and deterenol. Overall, they concluded that 89% didn’t accurately label their ingredients.

“Given these findings, clinicians should advise consumers that supplements listing botanical ingredients with purported stimulant or anabolic effects may not be accurately labeled and may contain FDA-prohibited drugs,” the authors concluded.

Despite the sketchy reputation of the supplements industry, Americans haven’t stopped buying them. 

The supplements market is worth more than $35 billion a year in the U.S., fueled by rising demand during the COVID-19 pandemic, and is expected to grow even further. And while it’s an unregulated industry, plenty of pharma companies like Bayer, Pfizer and GSK have taken slices of it with their own supplement businesses.

There are also thousands of users on social media, including TikTok in particular, that tout various supplements – from non-expert content creators to physicians. With the weight loss drug frenzy in recent months, TikTokers have even started a new trend around berberine, a supplement that they claim is a substitute for Ozempic or Wegovy.

However, the latest study is yet another reason for consumers to fully investigate supplement claims and labels before consuming these products.