Soy and Breast Cancer
- Terminology: Soy, Phytoestrogens, Isoflavones
- Does Soy Help Prevent Breast Cancer?
- What is the Effect of Soy on Breast Cancer Patients and Survivors?
- What are Some Other Benefits of Soy?
- Soy Content of Selected Foods
- Additional Resources and References
Researchers have also been exploring other possible benefits of soy. Again, the research on soy is relatively new and the effects have not been confirmed in large human clinical trials. A few recent studies have shown that soy foods containing phytoestrogens may mimic the benefits of hormone replacement therapy. In addition to relieving menopausal symptoms such as hot flashes, vaginal dryness or other menopausal symptoms, phytoestrogens may help prevent heart disease and osteoporosis, a degenerative bone disease. Preliminary research shows that soy may also help protect men against prostate cancer.
In a study conducted at the Stanford University Medical Center in California, women who were given a soy-based diet lowered their total cholesterol levels by 9% and LDL cholesterol levels ("bad cholesterol") by 13% compared to women who did not include soy in their diets. The FDA allows soy food labels to state that 25 grams of soy protein daily may help reduce the risk of coronary heart disease by lowering blood cholesterol levels. Phytoestrogens were also shown to protect against menopausal symptoms, osteoporosis, and decrease the risk for breast cancer in the study.
Researchers believe that phytoestrogens found in many soy foods may provide multiple benefits to women because they help balance hormone levels in the body. A lack of the hormone estrogen has been shown to increase the risk for osteoporosis and heart disease. However, too much estrogen may contribute to breast or uterine cancer because some cancer cells depend on estrogen for survival.
Presently, the general consensus is that women at high risk of cardiovascular disease could benefit from a soy diet, especially if they do not have a family or personal history of breast or uterine cancer. However, because the benefits of soy need to be confirmed in larger clinical trials, physicians do not generally recommend soy as the only treatment or means of protection against heart disease, osteoporosis, or menopausal symptoms (such as hot flashes, vaginal dryness, etc.).
The FDA has recently granted approval to the use of soy food labels that contain a phrase equivalent to: "25 grams of soy protein daily can reduce the risk of coronary heart disease by lowering blood cholesterol levels."
Soy Content of Select Foods
|Food||Amount of Soy|
|3 ounces water packed tofu
3 ounces silken firm tofu
8 ounces plain soy milk
8 ounces vanilla soy milk
¼ cup (one ounce) soy nuts
2 tablespoons soy nut butter
2 scoops protein powder (1/3 cup)
1 soy burger
1 soy breakfast patty
½ cup tempeh
½ cup cooked/canned soybeans
1 soy protein bar
Source: U.S. Soyfoods Directory
The United States Department of Agriculture (USDA) has also collaborated with Iowa State University to create a database that catalogues the amounts of genistein, daidzin, and total isoflavones found in foods.
- The July 15, 1999 American Cancer Societys News Today report, "Effects of Soy on Breast Cancer Risk Still Unknown," is available at http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Soy_and_Breast_Cancer.asp
- The May 3, 2000 Imaginis.com report, "Phytoestrogens (Soy) Show Similar Benefits of Hormone Replacement Therapy And May Help Prevent Breast Cancer," is available at http://www.imaginis.com/breasthealth/news/news5.03a.00.asp
- The February 1, 2000 Imaginis.com report, "New Research Shows Soy May Prevent Breast Cancer," is available at http://www.imaginis.com/breasthealth/news/news2.01.00a.asp
- Several abstracts from studies on soy presented at the third international symposium (Oct.-Nov. 1999) on "The Role of Soy in Preventing and Treating Chronic Disease," are available on the U.S. Soyfoods Directory website at http://soyfoods.com/
Updated: September 10, 2007