All dietary supplements come with inherent risks because they remain largely unregulated by the FDA. That means the various pills and powders on the market don’t have to back up any of their health claims, and they can even include ingredients never tested on humans. Some products are labeled incorrectly, failing to disclose certain substances or claiming ingredients that are actually absent. That doesn’t mean every nutritional supplement will damage your health, but it does mean that all of these products have the potential to do some amount of harm. In fact, a study published in the British Journal of Cancer uncovered a significant link between muscle-building supplements and testicular cancer.
Researchers focused on a range of muscle-building supplements, citing the sharp surge in their use as well as previous studies linking certain ingredients to testicular damage. One study, for example, linked large quantities of creatine to increased production of formaldehyde, a substance that caused testicular damage in rats in a separate study. In 2005, researchers found a high prevalence of performance-enhancing supplement use among people diagnosed with testicular cancer.
In the study from Yale University, supplement use included ingredients such as creatine, protein, and androstenedione. About 900 men ages 18 to 55 participated, more than 350 of whom had been diagnosed with testicular germ cell cancer. The researchers measured a range of factors that could influence cancer risk, such as smoking, drinking, exercise habits, past groin injuries, and whether they’d ever taken muscle-building supplements regularly at any point. After controlling all other factors, they found men who used muscle-building supplements were more likely to develop testicular cancer than those who did not, especially if they started before age 25, took more than one supplement, or used the supplements for three or more years.
Overall, men who consumed these products increased their risk by 65%. Men who used more than one type of muscle-building supplement nearly doubled that risk.
The study has prompted some criticism from groups like the Council for Responsible Nutrition, a leading trade association for the supplement industry, which pointed out a few limitations of the study. Most notably, the study doesn’t actually name supplements used by the study’s participants, which included 30 different types of powders and pills. This makes it difficult to pinpoint which ingredients are harmful. It should also be noted that androstenedione, one of the ingredients found in some products, is not currently legal. In 2004, USDA banned the sale of androstenedione, claiming the drug poses health risks commonly associated with steroids.
The limitations of the research notwithstanding, it is the first analytical epidemiological study of the possible link between supplements and testicular cancer. The study’s authors hope the results will prompt further research. “Our study found that supplement use was related to a higher risk of developing testicular cancer,” said Russ Hauser, professor of environmental health science at Harvard T.H. Chan School of Public Health and a co-author of the study. “These results are important because there are few identified modifiable risk factors for testicular cancer.”
Genes and family history factor into the likelihood that someone will develop testicular cancer, but these factors alone don’t account for the increased rates of testicular cancer in the past few decades. Tongzhang Zheng, the study’s senior author, said incidence of testicular cancer rose from 3.7 cases per 100,000 men in 1975, to 5.9 cases per 100,000 in 2011. Survival rates of testicular cancer are high, but researchers still know very little about the disease’s causes and risk factors.