Men who take body-building supplements such as creatine or androstenedione have up to a 177 percent higher chance of developing testicular cancer than men who don't, new research suggests. And the risk is worse if you started using young.
It's very preliminary work, but the results could help to explain why testicular cancer has become far more common (more than 1.5 times more common, to be precise) than it was in the '70s, along with society's growing consumption of supplements.
"The observed relationship was strong," said epidemiologist and study-leader Tongzhang Zheng, from Brown University in the US, in a press release. "If you used at earlier age, you had a higher risk. If you used them longer, you had a higher risk. If you used multiple types, you had a higher risk."
This is the first study to link testicular cancer to body-building supplements, but it was inspired by earlier research that suggested body-building supplements, namely androstenedione, could damage the testes.
To work out what was going on, the team conducted detailed lifestyle interviews with nearly 900 men in the US - 356 of them had been diagnosed with testicular cancer, while 513 had not. They asked about how often they were using supplements, but also about other potential risk factors, such as smoking, drinking, exercise habits, previous injuries to the region, and family history.
After taking into account all these factors, the team found that men who took muscle-building supplements had on average a 65 percent greater risk of developing testicular cancer compared to those who didn't. And this risk increased to 177 percent if the men used more than one type of supplement. It also shot up significantly if the men had started using supplements before the age of 25, or for more than three years.
The results have been published in the British Journal of Cancer, and offer epidemiologists an important insight into what causes the poorly understood cancer, and why it's on the rise. "Testicular cancer is a very mysterious cancer," said Zheng. "None of the factors we've suspected can explain the increase."
Of course, correlation doesn't equal causation, and more work needs to be done to find out exactly what's happening here. But the researchers think they now have a solid lead to follow, and the best part is that, if this link is confirmed, it'll be simple and quick for men to significantly reduce their testicular cancer risk.