WASHINGTON: Men who take muscle-building supplements are at a higher risk of developing testicular cancer, a new study has warned.
Researchers found that men who use muscle-building supplements, such as pills and powders with creatine or androstenedione, are more likely to develop testicular cancer than those who do not, especially if they start before age 25, take more than one supplement, or use the supplements for three or more years.
"The observed relationship was strong," said study senior author Tongzhang 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," Zheng said.
The study is the first analytical epidemiological study of the possible link between supplements and testicular cancer, the authors wrote in the British Journal of Cancer.
"Our study found that supplement use was related to a higher risk of developing testicular cancer. These results are important because there are few identified modifiable risk factors for testicular cancer," said Russ Hauser, professor of environmental health science at Harvard TH Chan School of Public Health.
In the study, Zheng's research team conducted detailed interviews of nearly 900 men from Massachusetts and Connecticut - 356 of whom had been diagnosed with testicular germ cell cancer, and 513 who had not.
In the interviews, researchers asked the men not only about their supplement use but also about a wide variety of other possible factors such as smoking, drinking, exercise habits, family history of testicular cancer, and prior injury to their testes or groin.
After tallying their data and accounting for all those possible confounders, as well as age, race, and other demographics, the researchers found that the men who used supplements had a 1.65 odds ratio (65 per cent greater risk) of having developed testicular cancer compared to the men who did not use supplements.
The researchers defined "use" as consuming one or more supplements at least once a week for four consecutive weeks or more.
The odds ratios increased to 2.77 (a 177 per cent greater risk) among men who used more than one kind of supplement, and to 2.56 among men who used supplements three years or longer.
Men who started using supplements at age 25 or younger also had an elevated associated odds ratio of 2.21, the researchers calculated.