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Two of the most commonly used sports supplements may increase a man's risk of testicular cancer, British doctors say.

There are two supplements that are used by millions of serious athletes in the West seeking to build muscle. Using them raises a young male athlete's risk of developing testicular cancer by 65 percent. 

One of these potentially carcinogenic nutritional supplements is the controversial substance androstenedione. For about 30 years, American athletes have been using it as a substitute for injections of banned drugs such as testosterone. A man (or woman's) body uses androstenedione as an intermediary substance in the process of transforming cholesterol into testosterone and estrogen. Taken in the form of capsules, it provides the raw materials for making testosterone, which in turn stimulates muscle building and aggression.

Another of these potentially carcinogenic nutritional supplements is the far less controversial substance creatine. There are some creatine products that have received a US FDA designation of GRAS, generally regarded as safe, but creatine in general is not on the GRAS list. The human body makes its own creatine from the amino acids arginine and glycine to help cells all over the body store energy. The more creatine available to muscle, the longer it can perform. Creatine also helps with mental sharpness by providing the brain with more energy.

Greatly Increased Risk Of Testicular Cancer

British scientists have found that men use these muscle building supplements have a 65 percent greater risk of testicular cancer. Men who start using them before the age of 25 have an even greater risk of this painful, potentially fatal cancer that usually can only be treated by removal of the affected testicle(s) and aggressive chemotherapy.

Most men, of course, don't get testicular cancer. In the USA, a man has only a one in 263 chance of developing this particular kind of cancer at some point in his lifetime. Among body builders and athletes who start using androstenedione and creatine in their teens and early twenties, however, that risk rises to about one in 100. It's still far from a sure thing, but it begins to become sufficiently common that the risk is real and most athletes will know some man who has it.

The first symptom of testicular cancer usually is a dull pain in the abdomen. There may be a lump or hardened area in the testicle(s). This kind of cancer can cause gynecomastia, or breast enlargement, and later lumps in the lymph nodes all over the body. Rates of the disease are highest among White men, especially those of Danish or Norwegian ancestry, and also Hispanics and Native Americans. Black, Asian, and Pacific Island males are far less likely to develop the disease.

What's The Problem With Androstenedione And Creatine?

One of the major issues with the use of these two supplements is that Asian-made versions are often spiked with actual anabolic steroids, not just the chemicals the body can use to make steroids and sex hormones. These chemicals definitely increase the risk of cancer.

Even worse, however, are the effects of products that combine creatine with protein powder. Possibly because of contamination with steroids, these products can increase testicular cancer risk by up to 615 percent. Men who use these products have a three to four percent risk of the disease.

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  • N Li, R Hauser, T Holford, Y Zhu, Y Zhang, B A Bassig, S Honig, C Chen, P Boyle, M Dai, S M Schwartz, P Morey, H Sayward, Z Hu, H Shen, P Gomery and T Zheng. Muscle-building supplement use and increased risk of testicular germ cell cancer in men from Connecticut and Massachusetts. British Journal of Cancer 112, 1247-1250 (31 March 2015) | doi:10.1038/bjc.2015.26.
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