Obesity and breast cancer

Thursday, 13 October 2011 14:08

Breast cancer is the most common cancer among women and is the second leading cause of cancer death in women, after lung cancer. According to the American Cancer Society, 1 in 8 women will develop breast cancer in her lifetime.

Obesity has long been recognized as a risk factor for breast cancer, as well as cancers of the colon, endometrium, kidney, and esophagus. Combined with physical inactivity, obesity may account for 25 to 30 percent of cancers of these major organs, according to the National Cancer Institute.

Obesity also increases a woman's risk of dying from breast cancer after menopause.

An estimated 11,000 to 18,000 deaths from breast cancer in women over the age of 50 could possibly be prevented with better weight management.

How does obesity increase the risk of breast cancer?

The increased risk of breast cancer in obese women is due to elevated estrogen levels. Although estrogen is an important hormone in the development and function of the female reproductive system, higher than normal levels of estrogen have been shown to support the growth of breast cancer.

Estrogen may increase the risk of breast cancer because the hormone stimulates division of breast cells and may support the growth of tumors that respond to estrogen. About 80% of breast cancers rely on continued supplies of estrogen to grow once they are established. These are known as hormone-sensitive cancers.

Obesity and estrogen

Estrogen is produced primarily in the ovaries, but can also be produced by fat cells. After menopause, when the ovaries stop producing hormones, fat cells become the primary source of estrogen. Postmenopausal women who are overweight have estrogen levels that are 50 to 100 percent higher than normal, leading to a more rapid growth of hormone-sensitive tumors.

Breast cancer prevention

To reduce your risk of cancer, it is important to achieve and maintain a healthy BMI. Studies have shown that women who exercise regularly have lower rates of breast cancer.

Include cruciferous vegetables in your diet. Foods such as broccoli, cauliflower, cabbage, bok choy, and kale have been shown to stop the growth of cancer cells and protect against cancer.

Also watch your exposure to endocrine disruptors, which are chemicals that can mimic the function of naturally occurring hormones in the body. Synthetic estrogens are not easily broken down and can accumulate in the body's fat stores, including breast tissue. Examples of environmental estrogens include:

• Some pesticides
• Some food preservatives and food dyes
• Compounds used in plastics, including bisphenol A. Buy a BPA-free reusable water bottle and do not reuse disposable water bottles.
• Some phthalates, which are preservatives often used in skincare products.
• Byproducts of household cleaning products and detergents, including nonylphenol and octylphenol.