Time to rethink muscle-building powders?

Regular use of muscle-building supplements pills and powders is associated with a higher risk of testicular cancer, a new study suggests.

The findings, published in the British Journal of Cancer, show that using muscle-building supplements (particularly pills and powders containing creatine or androstenedione) at or before age 25, using more than one kind of supplement, and using the supplements for three or more years were all associated with an increased risk of testicular germ cell cancer.

“While this is the first analytical epidemiological study to link [muscle-building supplements] to human cancer risk, bodybuilding supplements have long been linked to other human health issues,” study researcher Tongzhang Zheng, a professor of epidemiology at Brown University who conducted the research while at Yale University, tells Yahoo Health.

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“It is hard at this stage to attribute this risk to specific listed substances,” he adds. “We must be aware that [muscle-building supplements] also contains undisclosed compounds. Some supplement ingredients may damage the testes.”

The study included interviews with nearly 900 men; 356 were diagnosed with testicular germ cell cancer, and 513 were not diagnosed with the cancer. The researchers asked them details about a number of testicular cancer risk factors, such as family history, exercise habits, smoking status, injury to testes or groin, and their drinking habits. They also collected demographic information such as age and race, and information on “use” (which was defined as consuming one or more supplements a week for four or more weeks in a row, or more) of muscle-building supplements.

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Researchers found that use of the muscle-building supplements was linked with higher odds of testicular cancer diagnosis. For instance, men who began using the supplements at or before age 25 had a 2.21 increased odds of testicular germ cell cancer.

And men who used more than one kind of supplement had a 2.77 increased odds (or 177 per cent higher risk), and men who used the supplements for three or more years had a 2.56 increased odds (or 65 per cent higher risk) of testicular cancer, the researchers found.

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Zheng notes that “this is the first analytical epidemiological study to assess the relationship,” and that more studies of its kind of are needed. The study only shows a link, and does not prove that taking the supplements causes testicular cancer.

However, “I am sure if future studies also support the link as we reported here, there will be the new debate whether [muscle-building supplements] should be regulated or not,” he says.