Study sheds light on how exercise reduces breast cancer risk Canadian researchers have discovered a possible explanation for exercise's positive effect on reducing breast cancer risk. In a report published in the December 1 2005 issue of the American Journal of Epidemiology http://aje.oxfordjournals.org/, Dr. Julia Knight and her colleagues at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto, Ontario discovered that increased levels of melatonin may be behind exercise’s protective benefit. The findings of a number of previous studies suggest that melatonin may be protective against breast cancer. Obtaining regular exercise has also been shown to be protective against the disease, but the mechanism behind this phenomenon has not been agreed upon. Dr Knight’s team measured levels of a metabolite of melatonin in the urine of 213 women who collected overnight samples during winter and summer. The participants also took periodic light measurements and recorded exposures. Although none of the light variables were determined to be related to melatonin levels, the women’s exercise levels emerged as the most significant associated factor, with duration of exercise appearing to increase the amount of melatonin produced. “It is possible that the protective effect of exercise with respect to breast cancer may operate in part through an effect on melatonin,” the authors concluded. “If we know that increased melatonin production could be an underlying reason for the protective effects of physical activity against breast cancer, then there is great opportunity for the scientific community to build on this knowledge and help women understand what steps they can take to reduce their risk of developing the disease," Dr Knight stated. Sharon Wood, Executive Director of the Canadian Breast Cancer Foundation - Ontario Chapter who contributed to the funding for the research, commented, "Our focus on primary prevention research was initiated with the long-term goal of building knowledge about how to stop breast cancer before it starts. We are encouraged by the findings of Dr. Knight's work, which could provide momentum for lifestyle changes that could lead to a healthier population and potentially reduce the incidence of breast cancer." December 1 2005 issue of the American Journal of Epidemiology http://aje.oxfordjournals.org/ Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.