A study has recently been published that showed a link between testicular cancer and muscle-building supplements. This is important news because muscle-building supplements are popular and are often viewed as safe.
This study was performed as retrospective interviews with matched controls. 356 men who had been diagnosed with testicular germ cell cancer were compared to 513 men who had not been diagnosed with testicular cancer. Aside from questions about taking muscle-building supplements, the men were asked about a wide range of potentially confounding factors such as history of smoking, use of alcohol, history of exercise participation, prior injury to groin or testes, history of undescended testes, and family history of testicular cancer.
After accounting for the potentially confounding factors, as well as age and race, the researchers found a strong association between the use of muscle-building supplements and testicular cancer:
- Almost 20% of study participants with testicular cancer had used muscle-building supplements.
- A 65% increased rate of testicular cancer if supplements had been used at least once a week for at least four consecutive weeks.
- An 177% increased rate of testicular cancer if more than one type of supplement had been used.
- An 156% increased rate of testicular cancer if supplements were used for at least three years.
- An 121% increased rate of testicular cancer if supplement use began at or before age 25 years.
- An 155% increased rate of testicular cancer if supplements were used that contained creatine and proteins.
Since this study was retrospective, it did not prove that muscle-building supplements cause testicular cancer. This study also was unable to show a mechanism whereby muscle-building supplements may cause testicular cancer. However, the researchers did a good job in interviewing a large number of men and the association demonstrated in this study is quite compelling. Furthermore, the data, beyond the 65% increased rate of testicular cancer for any use of muscle-building supplements, appears to support a causative role for these supplements in testicular cancer. For example, use of increased variety of such supplements, increased duration of use, and use at a younger age would all be predicted to lead to higher rates of testicular cancer if any use at all of muscle-building supplements can cause testicular cancer.
Why is this study important?
Testicular germ cell cancer is the most common solid cancer in men age 15-39 years. The incidence has been rising over time, from 3.7 cases per 100,000 men in 1975 to 5.9 cases per 100,000 men in 2011.
Muscle-building supplements, like all over-the-counter supplements sold in the United States, are sold and regulated like food products. In other words, supplements are treated by regulatory authorities like boxes of breakfast cereal. This is unfortunate, because MOST SUPPLEMENTS ARE MEDICINE, just like aspirin and antibiotics. While regulatory authorities, like the FDA, are not perfect, they do require an amazing amount of safety research on pharmaceuticals before they can be prescribed and sold.
Patients often tell me that they are nervous about taking medications after they have read the warning sheets that accompany these medications. But what these warning sheet show is that research has been done, often with tens of thousands of people, to carefully define all possible side-effects of these medications. Supplements that do not contain these warning sheets are NOT safer because of a lack of warning data. In fact, they are potentially LESS SAFE because safety research has NOT been done, due to a different type of regulation. To put it another way, most people should be reassured when they see detailed warning information and should be worried when they do not see such information.
How do these statements apply to muscle-building supplements?
- Natural components in these supplements could act like artificial hormones.
- Some of these supplements could contain impurities or less-active ingredients, which are not required to be listed on product labels.
- Some of these supplements may contain hidden, unlisted, ingredients such as androgenic steroids.
An example of hidden dangerous ingredients arose this year. A muscle-building supplement called Tri-Methyl Xtreme was found to contain synthetic anabolic (androgenic) steroids. These anabolic steroids can cause liver injury and other dangerous side effects. Since anabolic steroids are drugs, the FDA was able to crack down on this product and warn about its use.
Please be careful if you plan to take muscle-building supplements. You may do very well to stick to a healthy diet with lean meat and other non-laboratory sources of protein and other essential nutrients.
Stay healthy and safe! I’ll see you in the gym!
Li N, Hauser R, Holford T, et al. Muscle-building supplement use and increased risk of testicular germ cell cancer in men from Connecticut and Massachusetts. Br J Cancer. 2015 Mar 31:112 Suppl:1247-1250.