Irisin is a hormone that has the ability to destroy aggressive cancerous cells while leaving normal cells unharmed. Irisin is a newly discovered hormone that gets released from muscle cells after exercise. New research has shown this hormone may prevent breast cancer and boost the effects of chemotherapy drugs that are used in the treatment of breast cancer. Studies in the past have shown that women who exercise regularly have a 30 to 40 percent lower risk of developing breast cancer and a much better prognosis if they do get the disease. This might be partly explained by higher irisin levels caused by regular exercise. If irisin is added to cancerous cells in test tubes, it has the ability to kill them. In fact, there is a 22 fold increased rate of cancer cell apoptosis (cell death). Having high levels of this hormone in your bloodstream through regular exercise may help to offer protection against a range of different cancers. People who exercise while receiving treatment for cancer often end up faring better than sedentary people. Of course it is often difficult to exercise at that time because of severe fatigue and nausea. Please keep in mind that any exercise is better than none at all. If you don’t have the energy to go for a walk around the block, perhaps doing some Pilates, or toning your arms with hand weights is more achievable. Anything that works your muscles will release irisin into your bloodstream. My number one recommendation for reducing the risk of cancer is to ensure you are getting enough selenium and vitamin D. You can read the remarkable research about selenium here.   Reference: http://medicalxpress.com/news/2015-02-irisin-aggressive-cancer-cells-negatively.html"