Study demonstrates role of exercise in modifying melatonin levels

12/01/05

Increase believed to offer breast cancer protection

Toronto, ON – December 1, 2005: Moderate physical activity, which is believed to help reduce the risk of breast cancer, may do so because it increases production of a hormone believed to have protective effects against the disease, a Canadian research team has learned.

Researchers at Mount Sinai Hospital's Samuel Lunenfeld Research Institute in Toronto have completed a study of how light and other factors, such as physical activity, influence the production of melatonin – a hormone released mainly at night in the absence of light and believed to protect against breast cancer. The findings of the study have been published in the December 1, 2005 edition of the American Journal of Epidemiology.

The study is among the first to demonstrate the role of physical activity in potentially modifying melatonin levels, thus creating biological evidence for a reduced risk of breast cancer among women who exercise regularly.

"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," said Dr. Julia Knight, the study's lead investigator at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital and a University of Toronto professor in the Department of Public Health Sciences.

The study, funded through the Canadian Breast Cancer Research Alliance with special funding from the Canadian Breast Cancer Foundation - Ontario Chapter to study the modifiable risk factors for breast cancer, took place between 2002 and 2004 and involved the participation of 213 female volunteers whose melatonin levels were monitored over time.

"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," said Sharon Wood, Executive Director of the Canadian Breast Cancer Foundation - Ontario Chapter. "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."

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