Estrogen is a hormone which is primarily responsible for female development of breasts, regulation of the menstrual cycle, and is essential for normal functioning of the female organs. Estrogen is produced by the ovaries during a woman’s childbearing years. After menopause, the ovaries no longer make estrogen. Research has determined that the single greatest risk factor for future development of breast cancer is lifetime exposure of the breasts to estrogen (1).

Estrogen promotes an increase in growth of cells for the breasts and uterus during the menstrual cycle. When pregnancy does not occur, estrogen levels drop. The influence of cell division by estrogen increases the risk of mutated cells. Mutation of the proliferated cells can cause cancer. These mutations can be caused by exposure to radiation, carcinogenic chemicals, and spontaneously as a mistake when cells duplicate.

One of the most comprehensive genetic research studies published in 2010 by scientists at the Genome Institute of Singapore suggests that there is a central role of the metabolic pathway of estrogen in the carcinogenesis of breast cancer. “For the first time, we found compelling evidence that there is a strong link between occurrence in genes that metabolize estrogen and risk of both breast and endometrial cancer (2).” According to University of Illinois food science and human nutrition professor William Helferich, “About 70 percent of women with breast cancer have estrogen-responsive tumors.” The most common type of non-invasive breast cancer is called Ductal Carcinoma in Situ. This occurs when cancer develops within the milk ducts and has not spread into other tissue. Invasive Ductal Carcinoma is the most common invasive breast cancer. This cancer starts in the milk ducts but then spreads or metastasizes to other tissues of the body.

Since estrogen encourages the increase of milk ducts in the breasts, it would be a good idea to limit your exposure of estrogen and sources that may mimic estrogen. Studies from the National Cancer Institute have shown that breast tissue levels of estrogen may be up to 50 times higher than those found in laboratory blood tests. (3)

Common Sources of Estrogen

Soy Consumption
Foods made from soybeans have organic compounds called phytoestrogens which produce high levels of estrogen-like effects. Phytoestrogens of soybeans have been studied the most when linking foods to breast cancer. (4)

Types of Soy to Eliminate
“Soy Protein Isolate/Isolated Soy Protein”
“Hydrolyzed Vegetable Protein”
“Texturized Vegetable Protein”
“Soy Protein”
Soy Protein Supplements

Hormone Replacement Therapy
The Women’s Health Initiative study sponsored by the World Health Organization had to come to a halt when hormone replacement therapy including estrogen combined with progesterone started increasing the risks of heart disease and breast cancer.
Hormones can increase the growth of estrogen positive tumors, which carry receptors for estrogen on their cell surfaces. “The hypothesis is that when women stopped taking menopausal hormones, tiny cancers already in their breasts were deprived of estrogen and stopped growing, never reaching a stage where they could been seen on mammograms.” (5)

Birth Control Pills
Even the weakest birth control pill contains seven times the amount of estrogen naturally occurring in your body1. Monitoring your body’s menstrual cycle is the healthiest and most natural form of birth control. We encourage chemical free birth control such as the method described in the book, Love and Fertility by Mercedes Arzu Wilson.

Excess Body Fat
After menopause, when the ovaries stop producing estrogen, fatty tissue generates estrogen. Regular exercise can help balance one’s hormones and fight menopausal symptoms. Being ‘overweight’ is not what counts. It’s being “over fat” that’s the problem. You can be “thin”, yet a large percentage of your body weight can be fat.


  1. Mostovoy, Alexander. “Ten Ways to Help Prevent Breast Cancer”. Thermography Clinic Niagra. Web. 31, Aug. 2011
  2. Agency for Science, Technology and Research (A*STAR), Singapore. “Link between estrogen metabolism pathway and breast cancer risk discovered.” ScienceDaily, 5 Aug. 2010. Web. 29 Aug. 2011.
  3. Jefcoate, C.R., et al: Chapter 5 – Tissue-Specific Synthesis and Oxidative Metabolism of Estrogens. Journal of the National Cancer Institute, No. 27, 95-112, 2000
  4. Warren, Barbour S. and Devine, Carol Breast Cancer and Environmental Risk Factors in New York State. Cornell University, 2010. Web 30 Aug. 2011
  5. Kolata, Gina, Breast Cancer Rate Falls in U.S., Study Shows. New York Times, 14 Dec. 2006