I have uterine cancer. My doctor has told me to avoid all soy foods since they contain phytoestrogens. Do you think I need to avoid them?
Soy is a major component of East Asian diets. East Asians consume ten times the quantity of phytoestrogens in soy foods as the average American. Yet, Japanese women have decreased rates of hormone-dependent cancers such as breast and endometrial (uterine). Contributions from the diet to these benefits have become more evident as phytoestrogens have been increasingly studied. Data now suggest plant-based diets low in calories from fat, high in fiber, and rich in legumes (especially soybeans), whole grain foods, vegetables, and fruits may reduce the risk of endometrial cancer. (1, 2, 3)
An animal study has shown that feeding mice the two individual phytoestrogen molecules found in soyfoods helped to prevent uterine cancer. (4) However, there is one case report of a woman who developed uterine cancer after consuming an "excessive amount" of the phytoestrogen molecule from soy as an individual dietary supplement (i.e. in a pill, capsule, or powder form, not a soy food). (5) It is not known if the soy phytoestrogen caused her cancer but consuming an isolated molecule (much like a drug) could certainly induce actions in the body different from whole foods.
However, a study was recently published that may be of interest to your doctor (6). This study showed that consumption of 2 servings per day of soy foods for two years by pre-menopausal women did not have any effect on the levels of various estrogen compounds in the blood of these women.
One point to keep in mind when considering the answer to your question is knowing there are the many types of phytoestrogen molecules in a wide variety of plant foods, not just the ones identified in soyfoods. It is virtually impossible (and not desirable) to eliminate all of these plant foods and their phytoestrogen molecules from the diet.
Although there is currently no set requirement for intake of soy foods, the consumption of 1-3 servings of soy would be comparable to the Japanese' soy food intake. There are a wide variety of soy foods available at the store, including tofu, miso, tempeh, soymilk, and soy flour products.
I have been including 1-3 servings of soy foods in my diet since 1995 and have had no recurrence of my estrogen-dependent breast cancer.
All in all, I think the most important thing that someone with cancer should do is see a local Registered Dietitian to have all aspects of their diet reviewed and individualized with one's overall medical history, particularly if weight loss is also needed to reduce the risk of heart disease, diabetes, etc, etc.
I send you all my best wishes for health, healing, and hope.
Diana Dyer, MS, RD
(1) Goodman MT, et al, Association of soy and fiber consumption with the risk of endometrial cancer. Am J Epidemiol 1997:146(4):294-306.
2) Xu WH, et al, Soya food intake and risk of endometrial cancer among Chinese women in Shanghai: population based case-control study. BMJ. 2004 May 29;328(7451):1285.
(3) Horn-Ross PL, et al, Phytoestrogen intake and endometrial cancer risk. J Natl Cancer Inst. 2003 Aug 6;95(15):1158-64.
(4) Lian Z, et al, Preventive effects of isoflavones, genistein and daidzein, on estradiol-17beta-related endometrial carcinogenesis in mice. Jpn J Cancer Res. 2001 Jul;92(7):726-34.
(5) Johnson EB, et al, Phytoestrogen supplementation and endometrial cancer. Obstet Gynecol. 2001 Nov;98(5 Pt 2):947-50.
(6) Maskarinec G et al, Effects of a 2-Year Randomized Soy Intervention on Sex Hormone Levels in Premenopausal Women, Cancer Epidemiology Biomarkers & Prevention 2004 Vol.13,1736-1744.
answer was originally researched and written by Julie Bruce, RD, for
a graduate-level nutrition class at Eastern Michigan University. Updating
was done by Diana Dyer, MS, RD, June 2005.
faq posted 2/03, updated 7/05
These questions and answers are intended to be of a general informative nature. Please consult with the Registered Dietitian in your cancer center or your health care provider for nutritional advice that can be individualized to your specific medical condition.
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