Posts Tagged Breast cancer

Does walking affect the risk of developing breast cancer?

Graham Beaton BHSc, ND
Doctor of Naturopathic Medicine

Several studies have shown that the risk of developing postmenopausal breast cancer is lower in women who are physically active (1). To show this, studies typically compare breast cancer rates in women who participate in regular vigorous physical activity (jogging/running, tennis, racketball) to women who are physically inactive. While these studies clearly show why physical activity is important and suggest that postmenopausal women should participate in vigorous physical activity, many women will not participate in “vigorous” physical activity due to health concerns (for instance osteoporosis) or lack of interest. Thus a question that arises, is if a woman is unable or unwilling to participate in vigorous physical activity, can their risk of breast cancer be lowered with regular moderate physical activity (i.e. walking)? A recent study published in the journal Cancer Epidemiology, Biomarkers and Prevention looked to answer this question (2).

To explore the link between breast cancer and moderate physical activity, the researchers looked at cancer rates amongst postmenopausal women who participated in the CPS-II Nutrition Cohort (a prospective study of cancer incidence established by the American Cancer institute). The researchers collected information regarding levels of weekly physical activity (walking was the predominant form of physical activity) and categorized women into 3 separate groups: those who participated in moderate physical activity less than 3 hours per week, those active for 4 to 6 hours per week, and those who were active more than 7 hours per week.

Results of the study showed that women who were moderately physically active for more than 7 hours per week had a 14% lower risk of developing breast cancer compared to those who were moderately active for less than 3 hours per week. In accordance with previous results, results also confirmed that women who participated in vigorous activity had the greatest benefits, a 25% reduction in breast cancer risk.

These results provide evidence that physical activity even at a moderate level of intensity can have a large impact on one’s risk of developing breast cancer risk and overall health.

1. Friedenreich, CM. The role of physical activity in breast cancer etiology. Semin Oncol. 2010 Jun;37(3):297-302.

2. Hildebrand, J. S. et al. Recreational Physical Activity and Leisure-Time Sitting in Relation to Postmenopausal Breast Cancer Risk. Cancer Epidemiol Biomarkers Prev. 2013 Oct;22(10):1906-12

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Breast Cancer and Promoting Breast Health

Each year 5000 Canadian women will die because of breast cancer and another 24000 women will be diagnosed with breast cancer1. Breast cancer is a significant health concern for Canadian women. This article will discuss what breast cancer is, risk factors for the development of breast cancer, and steps that can be taken to attempt to minimize one’s risk of developing breast cancer.

The Normal Breast and Breast Cancer
The breast is composed of several different types of tissues, including fat and connective tissue, blood and lymph vessels, specialized glands (called lobules) that produce milk after a woman has given birth and ducts that transport milk. The tissues of the breast are controlled by various hormones and other growth factors that allow the breast to mature (during puberty), produce milk, and that allow for the normal repair and replacement of cells of the breast. Like all cells of the body, the cells of the breast have a normal life cycle, where they grow, die and are replaced with new cells, and this process occurs in a regulated manner. In cancer, this normal regulated cell growth is lost, and abnormal cells are allowed to continue to replicate, resulting in cancer. Specifically, breast cancer arises when there is abnormal growth in the cells of the lobules and their associated ducts.

Why Does Breast Cancer Occur?
Unfortunately it is not known why breast cancer occurs. While there are several risk factors for the development of breast cancer, it appears as though the onset of cancer might be influenced by a combination of risk factors occurring at once. For instance, one common risk factor is a genetic mutation in a specific gene, the BRCA1 gene. Normally, the BRCA1 gene works to produce proteins that fix errors in DNA synthesis during the production of new cells. When the genetic mutation exists, the DNA repair proteins are not produced, allowing cancerous cells to arise. Now, amongst women who carry the gene, approximately 55 to 65% go on to develop breast cancer by the age of 70 – which indicates that additional cancer promoting factors might need to be present for a woman to develop breast cancer2.

Additional risk factors for the development of breast cancer include: a woman’s age, personal and family history of breast cancer, early menstruation and late menopause, exposure to hormones (birth control pills, hormone replacement therapy), pregnancy and breast feeding, etc. Three additional modifiable risk factors include obesity, physical activity and alcohol use, which are discussed below.

Obesity and Physical Activity
Obesity is an established risk factor for the development of postmenopausal breast cancer. One reason for this is that fat tissue, especially fat around the waist, produces estrogen. The estrogen produced enters into circulation, where it may stimulate the cells of the breast, increasing both the risk that abnormal cancerous cells can arise, and/or stimulates the growth of breast cancer that is already present3.

Obesity has also been shown to influence several other cellular mechanisms that can increase the risk of developing breast cancer. These include increasing inflammatory factors present in the breast (which can cause damage to cellular DNA of the breast, potentially leading to the presence of abnormal/cancerous cells) and increasing the production of other cellular growth factors (e.g. insulin-like growth factor 1 (IGF-1)), which would increase the chance that abnormal (cancerous) cells are produced and/or stimulate existing cancer cells to grow/reproduce2-3.

In addition to one’s weight influencing her risk of developing breast cancer, one’s level of physical activity has also been linked to breast cancer2. Specifically, it has been shown that amongst postmenopausal women, those who are physically inactive have higher levels of estrogen in circulation. Again, this can increase the risk of cancer cells arising and can promote the growth of existing cancer of the breast. As well, physical activity has been shown to influence one’s level of the cellular growth factors, including IGF-1, such that a lack of physical activity is associated with higher levels of IGF-1 in circulation, and a subsequent increased risk of developing cancer4.

Alcohol and Breast Cancer Risk
Alcohol has consistently been shown to be associated with an increased risk of developing breast cancer. It was previously believed that alcohol contributed to breast cancer risk by increasing the levels of estrogen in circulation5. It appears now that this might not be the case as several studies have shown that alcohol ingestion does not have an effect on estrogen levels. Newer studies are now focusing on how alcohol may initiate the formation of cancerous cells by altering how DNA is replicated, how alcohol might affect the invasiveness of breast cancer cells and how alcohol might affect other hormones that can then be converted in to estrogen within breast tissue5.

In summary, while it is currently unknown why certain women will develop breast cancer, it is possible to reduce the risk of developing breast cancer by maintaining a healthy weight, being physically active and moderating alcohol use.
Graham Beaton is a Naturopathic Doctor in practice at Ottawa Collaborative Care Centres. If you are concerned about developing breast cancer, or if you have breast cancer and you would like to know how naturopathic medicine can help, please contact Graham at 613-290-6115.
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