Regular exercise reduces the risk of cancer and disease recurrence, yet the mechanisms behind this protection remain elucidated. In the last 3-4 years, fascinating discoveries about the impact of exercise on tumour growth have been made.

In a landmark study conducted in Sweden, a group of male participants were exercised on a bike for 60 minutes. Blood samples were taken from each individual both pre and post exercise. The blood samples were spun down and the serum extracted from each sample. This serum was then poured over a line of lab grown prostate cancer cells.

The results from the study demonstrated that the serum taken directly after exercise suppressed the prostate cancer cell growth by 31%. This finding suggests that during exercise a chemical is produced from the muscles and this chemical is leading to the destruction of tumour cells.

If this discovery wasn’t interesting enough, scientists in Denmark took this finding one step further. In a study deemed “one of the most pioneering cancer studies of 2016”, researchers explored the physiological mechanisms induced by exercise that lead to a reduced tumour growth and incidence.

Due to its pioneering nature, this study was conducted using mice. Mice with five different types of cancer including lung, liver and melanoma were split into two groups. The first group were given unlimited access to a running wheel whilst the second group had no access to any form of exercise.  Across all five types of cancer, exercise was found to reduce tumour growth by 60-70%. Another fascinating finding of this study was that the tumour cells in the mice that exercised were full of natural killer cells. Natural killer cells form a vital part of the immune system. These cells are responsible for the destruction of cells that are recognised as abnormal such as cancer cells.

Question: What is changing in the body through exercise that is causing the natural killer cells to be more active, seek out and destroy the tumour cells?

Answer: The researchers were able to demonstrate that exercise resulted in a signal that caused the natural killer cells to attack the cancer.

Signal 1: Adrenaline

Adrenaline produced during exercise activates the natural killer cells to be released into the blood stream. These cells are now primed for surveillance and looking for a target cell. This information then comes via the muscles. Exercise causes the muscles to release the second signal, a chemical called interleukin-6.

Signal 2: Interleukin-6 (IL-6)

IL-6 seeks out the tumour cells directly and also tells the natural killer cells what to target. The cancer cells are targeted and destroyed by the natural killer cells.

Although there may be other physiological mechanisms involved, this study is one of the first to show how exercise can up-regulate the immune system and make it more effective at fighting cancer. This study provides the evidence that through participation in exercise, the body has the ability to generate it’s own anti-cancer drug.