Breast cancer risk factors

In October (breast cancer month) JD Kato and I did a presentation at a local library about breast health and cancer prevention. Here is a summary of some of the more interesting information we shared. This first part will cover risk factors, which JD discussed. There are several non-modifiable risk factors that most people are aware of, such as age, gender, family history, etc. Let’s focus on risk factors you CAN modify…

Radiation exposure

Ionizing radiation such as x-rays can damage the DNA of cells promoting mistakes that could lead to development of cancer. The amount of radiation of a mammogram is considered small, but yes mammograms use radiation. Other sources of radiation may be from occupational accidents and radiation treatment.


Smoking raises your risk for many types of cancer: lung, esophageal, bladder, stomach, and others including breast cancer.


Postmenopausal women who drank alcohol had a 22% higher relative risk of breast cancer than those who do not drink alcohol. It is estimated that every additional 10g of ethanol consumed per day (approximately one drink) was associated with a 10% increase in relative risk.
Recommendation for alcohol intake for women: 0-2 drinks per day, maximum 9 drinks per week

Women's HealthEstrogen

Estrogen exposure can be a contributing factor to many breast cancers. Therefore, both exogenous (outside the body) and endogenous (inside the body) sources estrogen can increase risk.

Hormone replacement and birth control pills are exogenous sources that contribute to estrogen exposure that can be avoided.

Estrogen production within the body is also important. At puberty the brain (the pituitary) tells the ovaries to start to produce estrogen and because there are receptors in the breast tissue they are signalled to grow and develop. Although they grow in number, the cells of the breast tissue do not fully mature. With each monthly cycle there are fluctuating levels of estrogen, which can contribute to the cells that could possibly develop into cancerous cells. A first full-term pregnancy after the age of 30-35 contributes a slightly higher risk.

While a woman is pregnant, there are even high levels of estrogen and so the breasts enlarge to prepare for breast feeding – again putting a woman at higher risk. When a pregnancy reaches full-term and a woman breast-feeds, then the cells finish their maturation, which then helps protect against them developing into cancer. Breast-feeding for one year is protective against breast cancer. It does not matter if this period of breast-feeding is for one child, or combined over more than one birth.

Body fat and exercise

After menopause a woman’s ovaries do not produce estrogen as before, so most of the estrogen come from fat tissue. Estrogen comes from testosterone and in fat tissue there is the enzyme called aromatase that converts testosterone to estrogen. So having excessive body fat means you have more of these enzymes to produce estrogen which can stimulate cell reproduction in breast tissue and thus increasing the chance of tumour formation.

Excess body fat, especially around the midsection, promotes inflammation in the body, which is a risk factor for many cancers. Chronic inflammation disrupts normal cell growth and development, which can promote.

Excess body weight and low physical activity together may account for one quarter to one third of all breast cancer cases! Contrast that to 3-5% of breast cancer caused by heredity…

Recommendations for exercise: 30 min 3-5 days per week (initially), then 30-60 min 5-7 days per week

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