Workout Supplements Linked to Testicular Cancer

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A new study has found an alarming link between the use of muscle-building supplements and testicular cancer risk. Men who reported using these pills or powders regularly had a far greater risk of testicular cancer than those who didn't take these supplements. 

Although it's rarely deadly, testicular cancer is the most common cancer among men ages 15 to 35. Rates have been rising for decades, and doctors have not been able to pinpoint why. Genetics, family history, age, and undescended or abnormal testicles are the primary risk factors, none of which can account for the increasing prevalence. This mystery has prompted researchers to explore other, modifiable lifestyle factors to try to find culprits.

For this study, the researchers homed in on muscle-building supplements, citing both the sharp surge in use of these products and previous studies linking certain ingredients within them to testicular damage. They rounded up nearly 900 men ages 18 to 55, more than 350 of whom had been diagnosed with testicular germ cell cancer, the most common form. The researchers surveyed these men about a range of factors that could influence cancer risk, such as smoking, drinking, exercise habits, past groin injuries, and whether they'd ever taken muscle-building supplements regularly at any point. After controlling for all other factors, they determined that the men who'd used these products were also significantly more likely to have testicular cancer.   

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This association is startling, but there are key limitations to this research that make it almost impossible — even for the researchers — to identify which supplements may pose a significant health risk or why. The first issue is that they lumped 30 different types of pills and powders into one category that they called muscle-building supplements. "It's impossible to tell from this study what may be harmful and what's not," says John Travis, senior researcher and chemist at NSF International, the leading third-party certifier of dietary supplements. "There isn't enough detail on what exactly these men were taking. That said, it does show us that this issue needs more research."

The other compounding factor is that muscle-building supplements are among the most frequently adulterated products, adds Travis. They oftentimes contain illegal steroids and other unknown contaminants not listed on product labels. It's likely that some men in the study thought they were taking one thing, which may or may not have been safe, but in reality, they'd been getting an entirely different, potentially hazardous substance all along.

If nothing else, this study serves as yet another reminder to be extremely careful with dietary supplements, especially products intended to build muscle or fuel your workout. Since supplements don't require Food and Drug Administration premarket approval, there are constantly new products with new and untested ingredients cropping up. "Anyone can make a product, put a name it, and sell it," Travis says. "It's difficult to catch everything right away with the massive number of products and ingredients out there."

When shopping for workout supplements, your safest bet is to choose one of the 700-plus products that carry the NSF Certified for Sport seal. This stamp means that NSF International has audited the manufacturer's facility, tested the product for heavy metals and other contaminants, and ensured that the label accurately conveys what's in the supplement. "Both the NFL and MLB require that any supplement used in their locker rooms must be NSF Certified for Sport," Travis says. "They've vetted our program and agree that this certification is the best."

Also, stick to reputable national brands and always read ingredient lists carefully. "If a product lists a weird chemical name that ends in –one, that's an immediate red flag that it may contains a steroid," Travis says. And don't be bamboozled by claims that sound too good to be true. "You have to take these with a grain of salt," says Travis. "If you see claims like 'fast weight loss' or ‘supecharged metabolism,' that's a product you don't want to take. A lot of it choosing safe supplements is just about common sense."