A recent study carried out in Finland suggests that just 30 minutes of exercise a day can increase the proportion of tumour-fighting white blood cells in the blood of breast cancer patients.
Researchers from the University of Turku analysed 20 women diagnosed with breast cancer who had not yet started their treatments. The participants performed a moderate exercise session by pedalling a stationary bike for 30 minutes, adjusting the resistance according to their own preference. Blood samples were taken at three points in time: before they started cycling, during the exercise and after they finished.
The study focused on the different types of white blood cells present in the blood. Some of these cells have the ability to attack and destroy cancer cells, while others may, paradoxically, facilitate cancer growth. The results showed a significant increase in cytotoxic T cells and natural killer cells, which are known for their ability to destroy cancer cells. In contrast, regulatory T cells and myeloid-derived suppressor cells, which often promote cancer development, saw no change in their numbers.
When analysing the ratios of these white blood cells to total white blood cells, the researchers noted a marked increase in the proportion of natural killer cells, while the proportion of myeloid-derived suppressor cells decreased.
"The composition of the different types of white blood cells determines whether the immune system is more inclined to eliminate cancer or facilitate its growth. If the tumour environment has more cancer-fighting cells rather than cancer-favouring cells, the body will be in a better position to fight the tumour," explained Tiia Koivula, lead author of the study and PhD candidate.
The study revealed that, during exercise, the number and proportion of cancer-fighting cells increased in the bloodstream, while the proportion of cancer-promoting cells remained stable or decreased.
It is not yet clear whether these changes observed in the blood also occur in tumour tissues. In the study, most of the white blood cells returned to normal levels one hour after exercise. However, preclinical studies have shown that cancer-killing cells tend to migrate to the tumour area after exercise.
"Based on current knowledge, physical activity is considered beneficial for all cancer patients, and our recent study supports this idea," Koivula concluded.
