Moderate but regular exercise can help women avoid some of the side-effects of radiation treatment for breast cancer, U.S. researchers reported on Monday.

Researchers studied 20 women with breast cancer, and found the women who walked briskly 20 to 45 minutes three to five times a week during radiotherapy treatment maintained their levels of healthy blood cells.

Radiation therapy for cancer can cause a range of side effects, from sunburn to fatigue, anemia and depression. Patients often have fewer red blood cells and hemoglobin, which carries oxygen.

Women who did not exercise lost significant oxygen capacity, Jacqueline Drouin of the University of Michigan-Flint and colleagues wrote in the report, published in the journal Cancer.

The study, the first to investigate the effect of exercise during treatment, adds to research that shows regular exercise can prevent breast cancer and can aid in recovery from cancer.