Build muscle mass and muscle strength, and you’ll also build up protection against cancer. Researchers at the University of South Carolina reached this conclusion from a study they published in Cancer Epidemiology, Biomarkers and Prevention. The Americans studied over ten thousand men who had taken part in a trial at the Cooper Clinic in Dallas from the 1980s up to 2003. The men who could shift heavier weights with bench presses and leg presses were less likely to die from cancer.
The men had undergone a thorough fitness and medical check up in the eighties, so the researchers knew how fit their subjects were and how much fat they were carrying.
The researchers first published results of their study in 2008, reporting that strong men live longer and that muscle strength in particular protects against cancer. If you have average or high muscular strength your chance of developing cancer is thirty percent lower than if your strength level is low. A high strength level protects slightly better than an average strength level, but the difference is negligible.
The researchers discovered that muscle strength reduces the chance of developing a fatal form of cancer regardless of your bodyweight. The graph below shows the protective effect of muscle strength for different BMIs. Black = low strength level; grey = average strength level; white = high strength level.
Dividing the subjects up according to body fat produced the same results. You’re better off with a lower fat percentage, but even if you have a bit more fat in your body, muscle mass still has a protective effect.
Fitness protects against cancer. Best of all is being fit and strong: if you’re not fit, the protective effect of your muscular strength is less.
The researchers also looked at different types of cancer in their study. Body strength protected against all sorts of cancer except for prostate cancer. The protective effect was greatest for cancer of the digestive tract.
The researchers think that the protective effect of muscle mass comes from the fact that muscle cells remove anabolic hormones from the body. The hormones that are responsible for muscle growth, such as IGF-1, also stimulate the growth of tumours.
The researchers don’t beat about the bush when it comes to the implications of their study. “It is biologically plausible to reduce cancer mortality death rates among men by promoting regular resistance training involving the major muscle groups of the upper and lower extremities at least 2 days per week”, they write. “Resistance and aerobic exercise should complement each other.”
Cancer Epidemiol Biomarkers Prev. 2009 May;18(5):1468-76.