Soy Foods and Isoflavones: Cause or Inhibit Breast Cancer?

Term Paper (Advanced seminar), 2011

8 Pages, Grade: B



The impact of soy foods on potential breast cancer risk has been a topic of considerable investigation in the medical field. The primary importance of research on soy foods is derived from the fact that these foods are rich in isoflavones, which are supposedly associated with inhibition of breast cancer development (Messina & Wood, 2008, p.1). Isoflavones are mainly contained in soybeans. High soy food intake in Asian countries like Japan is said to have sparked research on the role of isoflavones on reduction of breast cancer in 1990s (Messina & Wu, 2009, p.1673). Some isoflavones such as genistein possess non-hormonal properties that are associated with breast cancer inhibition in women. Thus, it is highly prudent to say that there are several mechanisms by which soy may reduce the risk of breast cancer in women. However, recent epidemiological studies have provided evidence suggesting that isoflavones indeed promote breast cancer (Kang et al, 2010, p.1859). This is because isoflavones such as geinstein have been found to stimulate growth of breast cancer cells which are estrogen-sensitive in overectomized mice. Several in vitro studies have shown that isoflavones can both inhibit or enhance ability of drugs to fight breast cancer (Nagata, 2010, p.83). Thus, understanding of the effects of isoflavones on breast cancer is still vague. This paper explores whether consumption of soy foods and isoflavones cause or inhibit breast cancer in women. In section 1, definitions of Isoflavones, biological functions and endocrine therapies will be given. In section 2, supporting literature on the positive and negative effects of isoflavones will be discussed. In section 3, several studies will be used as examples to support the information provided in section 2.


If women consume soy foods high in isoflavones, they will reduce their risk of breast cancer.

Research question

The research question for this study was; “is it important for women to understand the benefits and risks associated with a diet containing soy foods?”


Efficacy of isoflavones has persistently been put under scrutiny, and patients have equally become confused on whether or not to consume soy foods (Nagata, 2010, p.83). Therefore, careful evaluation of the available evidence is a viable endevor. It is immensely important to identify the strengths and limitations of this alternative therapy of breast cancer. Therapeutic research has generated the need for statistical design and evaluation. As such, research on breast cancer treatments and therapies has been assigned an important role in the medical field and is seen as a means of reducing dependence conventional treatments (Messina & Wood, 2008, p.2). This research provides adequate information about the efficacy of isoflavones as a potential remedy for breast cancer in the world.

Section 1: Definition of isoflavones, biological effects and relative risk

Isoflavones are diphenolic compounds that are chemically similar to estrogens. Thus, they are elements of phytoestrogens. Phytoestrogens are plant-derived compounds that have biological properties of estrogens (Messina & Wood, 2008, p.2). As such, isoflavones can bind to alpha and beta estrogen receptors. There are three main types of isoflavones; genistein, daidzein and glycitein (Messina & Wood, 2008, p.2). Biological effects of isoflavones can be defined as the various actions which are activated by these diphenolic compounds. Some of these biological actions include: inhibition of cell development, enhancement of cell differentiation, stimulating apoptosis and cell proliferation (Nagata, 2010, p.83).

Tamoxifen and anastrozole, as used in this article, are the commonly used adjuvant endocrine therapies for patients with breast cancer (Kang et al, 2010, p.1857). However, they are mostly used for patients who have hormone-sensitive cancer. Relative risk of a disease can be defined as the risk of the disease relative to exposure to various factors. Thus, it is a ratio of probabilities for two distinct factions. Understanding the underlying effects of the isoflavones is important in order to assess efficacy of soy foods in inhibition of promotion of breast cancer. Biological effects of genistein and daidzein should therefore be evaluated.

Section 2: Supporting literature on effects of Soy food on breast cancer

Genistein, which is an isoflavone, is associated with various biological actions which reduce risks of breast cancer. According to Trock, Hilakivi-Clarke and Clarke (2006, p.460), genistein slows down the epidermal development of tyrosine kinase, which is associated with growth of mammary tumors (Nagata, 2010, p.83). In addition, this isoflavone inhibits the activity of topoisomerase II, therefore reducing risks for breast cancer, especially among postmenopausal women (Trock, Hilakivi-Clarke and Clarke, 2006, p.460). However, these anticancer effects occur only at specific experimental conditions.


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Soy Foods and Isoflavones: Cause or Inhibit Breast Cancer?
The University of Liverpool
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foods, isoflavones, cause, inhibit, breast, cancer
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Carol Nganga (Author), 2011, Soy Foods and Isoflavones: Cause or Inhibit Breast Cancer?, Munich, GRIN Verlag,


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