Here's a short piece from the NY Time's Science section about a study showing that living a healthy life style decreases breast cancer risk. This study emphasizes maintaining a normal body weight.
Obesity dramatically increases a woman's risk of developing breast cancer by 50-100%, the risk increasing "the older the woman gets and the longer she remains obese." (1) The reason being is that the abdominal fat cells convert steroid (fat soluble) hormones to estrogen. In the breasts, the additional estrogen created binds to the breast cells, promoting "cell division and potentially tumor growth." (2) Cancer cells are abnormal cell growth: the additional cell division cause the tumor growth. Adipose tissue (fat) contains an enzyme, aromatase, that converts steroid hormones into estrogen. After menopause, the ovaries and pituitary gland are no longer signaling for estrogen production through the monthly menstrual cycle. To compensate, the amount of aromatase in the adipose tissue increases to step up estrogen production. Obese women have higher levels of estrogen production taking place in the body fat of the hips and stomach, which increases during menopause, which raises the risk of tumors developing in the breast.
"Glucose [blood sugar] is the preferred substrate for cancer cells. . . [In a study] mice injected with aggressive mammary [breast] tumors were placed on 3 diets. After 70 days 95% of the mice on the low-sugar diet were alive. Of the mice on the moderate-sugar diet 67% were alive. And only 33% on a high-sugar diet were alive. Also 'moderate' alcohol consumption is associated with elevation in the risk for breast cancer from 50-100%." (3)
Phytoestrogens have a chemical structure similar to estrogen. They bind to the receptor sites on the breasts, preventing the body's estrogen from binding and causing tumor cell growth. The phytoestrogens that bind to the breast cell estrogen receptor sites have a weaker influence on breast cell production, so that it is less likely that tumors will form. Common food sources of phytoestrogens include: soy (tofu, tempeh, miso), flax and raw pumpkin seeds, clover and mung bean sprouts. Avoid powdered soy concentrate, these have caused some to develop Hashimoto's thyroid disease. (4)
Studies have shown that phytoestrogens increase the effectiveness of breast cancer treatments. Borage oil has shown to decrease the growth of breast cancer cells. (5)
Eating an organic diet, and limiting exposure to chemicals, including household cleaners, detergents, pesticides, food packaging (plastics leach into foods, especially when warm foods are put into plastic containers) is also important to reduce cancer risk. Chemicals and pesticides can change the DNA of cells, causing them to mutate into cancer cells. Studies have shown higher levels of pesticides and pollutants in fat and blood of women with breast cancer than in healthy women. (6) KB
1-6. Lahans, T. Integrating Conventional and Chinese Medicine in Cancer Care. Elsevier 2007; 92-102.