Soy and Breast Cancer
Study Reports Benefits of Soy Protein for Breast Cancer Survival
Review by the Medical Advisory Board of GNC
December 11, 2009
On December 9, 2009, scientists from Vanderbilt-Ingram Cancer Center in Nashville released the results of a study evaluating over 5,000 breast cancer survivors in China and compared their soy food consumption to survival after 5 years with this disease. They divided the women into four groups, based on how much soy they ate. Women with the lowest soy intake, about half a cup of soymilk per day, were compared to three higher groups, with the highest consuming about three cups a day.
What the researchers found were those Chinese women with the greatest amount of soy in their diet had the greatest survival rate and those with the lowest amount of soy intake had the lowest survival rate. After four years, 7.4% of those who ate the most soy had died, compared with 10.3% of those who ate the least soy. The authors noted that although soy food consumption among US women is substantially lower than among women in China it has been rapidly increasing in the U.S. Wheather similar results in Amercian women could be also seen is therefore unknown.
This study is considered to be especially important because although soy constituents, such as soy protein extracts (isoflavones) genistein and daidzein have been shown to have anticancer properties, improve cardiovascular and bone health, they also have the estrogen-like effects. For this reason there is conflicting data from earlier studies evaluating the role of soy in stimulating cancer reoccurence in breast cancer survivors.
Perhaps even more importantly the study showed that protective effects of soy consumption did not appear to vary whether the women were pre or post menopausal, or whether their breast tumor was estrogen sensitive or not.
Breast cancer is the leading cause of cancer death in women between the ages of 15 and 54, and the second cause of cancer death in women 55 to 74. It is the scourge of modern society, and increasingly factors such as obestity, smoking and other life choices appear to be keeping the incidence of breast cancer elevated in the U.S. Better diet choices, such as the Mediterranean diet for redcucing the risk of heart disease, continue to link the healthy food choices to health benefits.
Soybeans have been cultivated in China for over 5,000 years. Both soy food products and processed soy protein isoflavones, used as protein supplements, continue to be a popular food protein source and additive to foods. Soybeans are a complete protein because soy contains all of the essential amino acids the body requires. Soy is often used as a substitute for dairy products.
This study and the results are impressive by helping to answer concerns about soy food products and existing breast cancer. It is still important to consult with your healthcare provider before making any significant changes in your diet.
The Medical Advisory Board of GNC is dedicated to provide you the latest news you can use to allow you to live well.
Sources:
1. Xiao Ou Shu; Ying Zheng; Hui Cai; et al., Soy Food Intake and Breast Cancer Survival, JAMA. 2009; 302(22): 2437-2443
2. http://www.cancer.gov/cancertopics/types/breast
3. http://lpi.oregonstate.edu/infocenter/phytochemicals/soyiso/
4. Setchell KD, Cole SJ. Variations in isoflavone levels in soy foods and soy protein isolates and issues related to isoflavone databases and food labeling. J Agric Food Chem. 2003;51(14): 4146-4155
5. USDA-Iowa State University Isoflavones Database. United States Department of Agriculture [Web page]. March 15, 2002 http://www.nal.usda.gov/fnic/foodcomp/Data/isoflav/isoflav.html.
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