Women's Nutrition

		Lona Sandon, MEd, RD/LD Section Editor, Current Trends in Nutrition Section Editor, Women's Nutrition - Assistant Professor, Department of Clinical Nutrition; UT Southwestern Medical Center at Dallas - American Dietetic Association Spokesperson

Soy Foods Role in Breast Cancer
Posted: October 2005
Source: Lona Sandon, MEd, RD/LD

Soy based foods have been promoted to assist in the treatment or prevention of a range of health issues including menopause, heart disease, osteoporosis, and hormone related cancers including breast cancer. Studies of soy's role in breast cancer have been contradictory. Does it prevent or promote breast cancer in those that are high risk? How much soy should be eaten and at what stage of life to decrease a women's risk? Despite the scientific controversy, many women nevertheless report eating soy for better breast health.

More than 450 women with a family history of breast cancer took part in a research study lead by the Fox Chase Cancer Center in Pennsylvania . The researchers evaluated each participant's diet pattern to determine the amount and quality of soy included in the diet as well as reasons why the participants include or don't include soy in their diet.

Researchers found that almost a third of the participants rated their selves as soy consumers. Of the soy consumers, almost half believe that eating soy will reduce their risk of cancer. Forty-three percent reported eating soy foods at least one time per month. “I try to eat healthy” and “I like the taste” were cited by more than 60% of the soy consumers as reasons for consuming soy. A little more than 50% believe soy foods are lower in fat than their animal counterparts. Vegetable burgers, tofu, soy nuts, and soy milk were the most commonly used soy foods. Lastly, soy consumers were also more likely to eat more fruits and vegetables and exercise more than non-consumers.

Of the women who reported not eating soy, reasons included not knowing how to prepare it, didn't like the taste, products hard to find, and did not believe that the soy foods were healthier.

Soy consumers and non-consumers obtained most of their information about the health benefits of soy from friends, newspapers, and magazines. Other sources include health newsletters, the Internet, product packaging, and health spas. Few sought information from a health professional.

Asian women who consume a soy based diet have a lower incidence of breast cancer. The extent to which soy may be able to reduce risk of breast cancer is unknown. Recent studies have reported a relationship showing that as soy or isoflavone (estrogen-like substance found in soy foods) intake goes up, breast cancer risk goes down. The average consumption of soy foods in this study was only six to seven servings per month, well below the typical Asian diet pattern and below the two servings per day or almost 50 milligrams of isoflavones used in studies that support soy in breast cancer risk lowering. In addition, evidence supports that isoflavone intake during adolescents may be cancer protective later in life.

On the contrary, these same isoflavones may be cancer promoting in women with a high risk of breast cancer. Isoflavones mimic estrogen and high levels of estrogen over a lifetime have been associated with higher risk.

Bottom line: Insufficient scientific information exists to make recommendations for soy consumption and lowering the risk of breast cancer. Lowering your risk may have more to do with your overall lifestyle including physical activity, low-fat diet, high fruit and vegetable intake, and alcohol intake than any effects of soy. See a registered dietitian to help you plan a balanced diet including low-fat soy based foods.  

Resources:

American Cancer Society. Soy and Breast Cancer.

Fang CY, Tseng M, Daly MB . Correlates of Soy Food Consumption in Women at Increased Risk for Breast Cancer. J Amer Diet Assoc. 2005;105(10):1552-1558.

United Soybean Board Talksoy.com