Breast cancer: a review of the environmental risk factors

Several factors that slightly or moderately increase the risk of breast cancer

• Obesity, particularly after menopause. Indeed many breast cancers are sensitive to estrogen. Fatty tissue produces small amounts of estrogen. If an individual has a lot of fatty tissue, the risk of developing breast cancer may increase.
• Hormonal contraceptives. Oral contraceptives containing estrogen and progesterone slightly increase the risk of breast cancer, particularly in women who use them long-term (more than 10 years). The good news, however, is that this risk falls when the contraceptive is no longer taken.
• Hormone replacement therapy (HRT) during menopause. Several studies have shown that prolonged use of HRT, in particular when it involves both estrogen and progesterone (combined HRT), slightly increases the risk of developing breast cancer. Here again, the risk appears to decrease a few years after treatment stops.
• Late pregnancies or no full-term pregnancies. Pregnancy temporarily halts the mammary cells’ exposure to estrogen and reduces a woman’s number of menstrual cycles. A pregnancy brought to term before the age of 20 slightly reduces the risk of developing breast cancer, whereas having a first child after the age of 30, or not having any children, increases the risk.
• Alcohol consumption. Consuming even small quantities of alcohol increases the risk of developing breast cancer, and the risk increases in proportion to the amount consumed. Alcohol is liable to increase estrogen production. Furthermore, it reduces the presence of certain nutritional elements such as vitamins A, B and C, which normally protect against cellular lesions.
• Consumption of fatty meat also seems to slightly increase the risk.
• Type-2 diabetes. This raises the risk not only of developing breast cancer but of dying from it.