A new study links taking muscle-building supplements, such as pills and powders with creatine or androstenedione, with an increased risk of testicular cancer.
Moreover, says study senior author Tongzhang Zheng, the associated testicular germ cell cancer risk was especially high among men who started using supplements before age 25, those who used multiple supplements, and those who used them for years.
“The observed relationship was strong,” says Zheng, who led the study at Yale University before joining the Brown University School of Public Health as a professor of epidemiology.
“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.”
Testicular cancer incidence rose to 5.9 cases per 100,000 men in 2011, from 3.7 cases in 100,000 in 1975, Zheng says. Researchers aren’t sure why.
“Testicular cancer is a very mysterious cancer,” he says. “None of the factors we’ve suspected can explain the increase.”