Breast cancer risk can be reduced through physical activity, according to new data published in a journal of the American Association for Cancer Research, called Cancer Epidemiology.

Aerobic exercise may prove to be a very effective means of lowering one’s risk of developing breast cancer.

Breast cancer is the most common invasive cancer in females worldwide. It accounts for 16% of all female cancers and 22.9% of invasive cancers in women.

Recently, researchers in the Journal of the National Cancer Institute identified an alteration in a gene, which affects the breakdown of estrogen and is also related to a modest reduction in breast cancer risk in pre-menopausal women.

The authors discovered that one of the ways in which aerobic exercise reduces the risk of developing breast cancer is by altering the way that estrogen is broken down and metabolized.

Aerobic exercise increases the ratio of “good” to “bad” metabolites of estrogen.

Mindy S. Kurzer, Ph.D., professor in the Department of Food Science and Nutrition at the University of Minnesota in Saint Paul, said:

“Observational studies suggest physical activity lowers breast cancer risk, but there are no clinical studies that explain the mechanism behind this. Ours is the first study to show that aerobic exercise influences the way our bodies break down estrogens to produce more of the ‘good’ metabolites that lower breast cancer risk.”

The researchers conducted a clinical trial called “Women in Steady Exercise Research (WISER)”. The trial included a total of 391 young and healthy premenopausal women.

They split the women into two groups with matching age and body mass indexes (BMIs).

The control group (179) led a sedentary lifestyle throughout the whole study period, whereas the intervention group (212) did half an hour of aerobic exercise five times a week for a period of 16 weeks.

The researchers made sure that the intensity of the exercise was the same for all the women. As part of their workout routine, the women used treadmills, stair steppers or elliptical machines.

Most of the participants completed the study (86% from the control group and 78 percent from the intervention group).

24-hour urine samples were collected on three consecutive days before the study and on three at the end. The researchers used a novel technique for measuring the estrogen levels, called liquid chromatography/tandem mass spectroscopy, to identify the quantity of three parent estrogens (E1, E2 and E3) as well as nine metabolites.

A reduction of breast cancer risk has been associated with the increased production of a metabolite called 2-hydroxyestrone (2-OHE1) as opposed to one called 16alpha-hydroxyestrone (16alpha-OHE1).

The researchers found that aerobic exercise caused an increase in the amount of 2-OHE1 and a decrease in amount of 16alpha-OHE1, which subsequently meant that their risk of breast cancer decreased.

Kurzer concluded:

“Exercise, known to favor fitness and improve heart health, is also likely to help prevent breast cancer by altering estrogen metabolism. It is very important, however, to decipher the biological mechanisms behind this phenomenon.”

A previous study published in the journal CANCER similarly identified a link between physical activity and a reduced risk of breast cancer, which showed that women can reduce their breast cancer risk by exercising and maintaining their body weight.

Written by Joseph Nordqvist