If you pop some pills to supercharge your workouts, bulking up might not be the only result: Using muscle-building supplements is linked to an increased risk of testicular cancer , researchers from the Yale School of Public Health found.
In the study, men who reported ever using over-the-counter muscle-building supplements—including creatine, protein powders, and androstenedione—were 65 percent more likely to develop testicular cancer than those who never took them.
Let’s give these numbers some perspective: Out of the 356 guys studied with testicular cancer, 19 percent of them reported using muscle-building supplements for at least once a week for four consecutive weeks. In the comparison group—which was made up of 513 cancer-free men—12 percent said they similarly used supplements.
After crunching the data to take into account several factors that could raise the risk, the researchers came up with the statistically-significant increased risk of 65 percent, meaning the relationship is unlikely to have occurred by chance.
What’s more, they found the risk was even greater for men who started popping before age 25, used two or more types of supplements, or took them for more than three years.
“It’s not just the listed ingredients or chemicals in the supplements which are the concern,” says study author Tongzhang Zheng, D.Sc.
The researchers aren’t sure what may be responsible for the link, but they believe it may be due partly to undeclared ingredients that often lurk in OTC supplements. And these may somehow be harming the testes, either in their original forms or as they are broken down in the body.
In fact, they cited a 2004 international study that found 15 percent of nutritional supplements tested contained anabolic steroids that weren’t on their labels.
10 Worst Things That Can Happen to Your Penis
But How Strong Is the Evidence, Really?
The problem, though, is that it’s not possible from the study’s design to isolate which of these supplements may be driving the relationship. That’s because the researchers lumped 30 muscle-building supplements together.
So we don’t know if the supplement-popping guys who developed cancer were taking things like simple protein powders or more serious products like androstenedione—which the FDA has declared a “steroid precursor” because it’s converted to testosterone in the body.
Plus, most of the participants who took supplements popped multiple kinds, said Zheng. That could further muddy what’s actually going on.
And those aren’t the only flaws in the study, says Larry Lipshultz, M.D., a urology advisor for Men’s Health. Another important issue was the groups of men studied: When you’re comparing two groups—the cases, or those who actually have the condition—and the controls—a healthy group without the condition—they should be as equally matched as possible.
But in this study, the group with testicular cancer had a higher proportion of guys who suffered previous groin injuries. That means they were more likely to have undergone some kind of medical evaluation, like an ultrasound, which would have detected testicular cancers earlier, says Dr. Lipshultz.
What’s more, certain muscle-building supplements that contain testosterone—say, if it’s an undeclared ingredient lurking in your bottle—can actually shrink your testicles, he says.
This can make testicular cancer easier to find. So it might not be that those ingredients are causing cancer, but may instead allow it to be detected earlier. In fact, hormones aren’t even thought to fuel men’s testicular tumors, Dr. Lipshultz says.
So Should You Shelve Your Supplements?
Bottom line: These findings aren’t enough to say men should avoid taking muscle-building supplements, says Dr. Lipshultz. But it should serve as a reminder to make sure you know what’s actually in your OTC supplements.
That means avoiding sketchy online stores and instead sticking to reputable brands. Check to make sure your supplements contain seals of approval by ConsumerLab.com or the U.S. Pharmacopeial Convention—that’ll mean the bottle actually contains what it says it does.
The Better Man Project
