People using muscle-building supplements containing creatine or androstenedione have a significantly higher likelihood of developing testicular cancer than those who do not use such supplements, according to a new study published in the British Journal of Cancer.
Senior author Tongzhang Zheng says the risk is 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,” said Zheng, who led the study at Yale University. “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, who is now at Brown University, said. Researchers aren’t sure why.
“Testicular cancer is a very mysterious cancer,” he said. “None of the factors we’ve suspected can explain the increase.”
The study is the first analytical epidemiological study of the possible link between supplements and testicular cancer. The work was inspired by mounting evidence that at least some supplement ingredients may damage the testes.