Sporting codes struggle to get athletes to stay away from performance enhancing drugs, but now a form of persuasion more effective than any testing regime may have emerged. Doctors can warn those thinking of "juicing," at least the males, that the balls at stake are more personal than the ones usually kicked or thrown.
In the British Journal of Cancer, Brown University professor Tongzhang Zheng investigated an association between the use of muscle-building supplements (MBSs) and testicular cancer. Surprisingly, Zheng says, “No analytical epidemiological study has examined” this before.
The study was done using the case-control method. Rather than finding a huge number of people who take supplements and waiting to see how many get cancer, Zheng went in the other direction. He found 356 men being treated for testicular cancer in Connecticut and Massachusetts and compared them with 513 controls of similar age, background and lifestyle.
Zheng found that MBS users were 1.65 times as likely to get testicular cancer as those who did not use the supplements. Moreover, Zheng says, “If you used at [an] 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.” The danger more than doubled for those who started using before they turned 25, as well as for those who used for more than three years or used more than one kind.
The findings may explain the rise of testicular cancer, which in the U.S. has gone from 3.7 to 5.9 cases per 100,000 men from 1975 to 2011. The rise has been even more dramatic in the U.K. and in Western Europe, while the disease remains rare in Africa and Asia.
“Testicular cancer is a very mysterious cancer,” said Zheng. “None of the factors we’ve suspected can explain the increase.”
The association is consistent with anecdotal reports and scientific evidence that molecules that mimic the effects of testosterone (or can be converted to it) shrink the testicles and affect their performance.
"Considering the magnitude of the association and the observed dose-response trends, muscle-building supplement use may be an important and modifiable exposure that could have important scientific and clinical importance for preventing testicular germ cell cancer development if this association is confirmed by future studies,” the authors conclude.
The research was done on supplements such as creatine and androstenedione. Establishing whether particular supplements are more harmful than others would require a much larger study. Zheng restricted his research to germ cell tumors, but as these represent 95% of testicular cancers, this barely affects the results.
Testicular tumors represent one of the most treatable forms of cancer, with five-year survival rates at 95% where modern medical facilities are available. Consequently, it represents a very small proportion of deaths from the disease. However, in countries where it is common, it represents one of the greater threats to men aged 15-49.