Soy, Phytoestrogens and Breast Cancer

Breast cancer is increasingly attacking women lately. Generally, it begins with a painful lump or tumors. In most cases, painful lumps are harmless cysts or fluid-filled sacs, but not always. Breast cancer cells can grow into lumps of 1 cm2 within 8-12 years (Tambunan, 2003). Other signs that are less common are breast pain, erosion, tightening, enlargement and itching of the nipples; or redness, enlargement or contraction of the breasts. If the cancer has spread (metastases stage), bone pain, jaundice or weight loss can occur (Bosman, 1999).

Some of the risk factors for breast cancer triggers are cigarette smoke, alcohol consumption, a long distance between age at first menstruation (menarche) and menopause, age at first birth, families who have a history of breast cancer, obesity and a high-fat diet, productive age and above, first pregnancy in old age, and hormones.

Research at the One-Stop Oncology Clinique at Dr. Soetomo Hospital, Surabaya, East Java, showed that women who were suffered from breast cancer are 46-55 years old. Hormones are thought to help increase the risk of breast cancer where 61.5% of women who used hormonal birth control developed breast cancer. Women who used hormonal birth control were 2.304 times more likely to develop breast cancer than women who did not use hormonal birth control.

Estrogen hormone has a very vital role for female reproductive function, and also increases bone density and prevents bone loss. However, this hormone is suspected to trigger the growth and spread of several types of tumors that cause breast cancer. About 50% of cases of breast cancer are cancers that are estrogen dependent or influenced by this hormone (Gibbs, 2000).

Breast cancer that is dependent on the hormone estrogen is known as a hormone-dependent type (hormonal dependent), the determination is if the estrogen receptor is positive. This type is not inherited from mother to daughter. It can be detected with the results of immunohistochemical tests of cancer tissue obtained from breast surgery.

Most breast cancer sufferers have cancer cells with estrogen receptor (ER) positive. While breast cancer that responds to changes in progesterone hormone levels is referred to  progesterone receptor (PR) positive.

How to control the hormone estrogen is by blocking estrogen receptors (injections that inhibit the production of estrogen in the ovary) or stop making estrogen in the body (surgical removal of one or both ovaries as the main source of estrogen production). This can cause early menopause in patients.

Can soy containing phytoestrogens triggers cancer?

Phytoestrogens are compounds in plants whose chemical structure resembles the structure of the estrogen sex hormone. However, phytoestrogens are weaker than the hormone estrogen inside the body.

Some foods that contain phytoestrogens are garlic, soybeans, rice, wheat, coffee, potatoes, vegetables like carrots and beans, fruits like apples, cherries, pomegranates. The two main groups of phytoestrogens are the isoflavone compounds, contained in soybeans and other legumes and their products; and lignans, contained in grains, flaxseeds, nuts, fiber and fruits, and also vegetables.

Is Phytoestrogens Harmful?

The effect of foods containing phytoestrogens on cancer is still being debated. Many studies have shown that phytoestrogens are beneficial i.e. decrease blood pressure, increase the control of blood glucose, decrease cholesterol levels, and reduce inflammation.

A phytoestrogen research in female rats showed an increase in estrogen levels in addition to the capacity of antioxidant properties (Setyawati et al., 2019). Other research on the provision of tempeh flour made from soybeans rich in phytoestrogens (isoflavones) could increase levels of the hormone estrogen, as well as calcium and phosphorus levels in the blood plasma of normal female rats (Suarsana et al., 2012).

One risk factor for breast cancer is high estrogen levels. Concerns arose when research found that phytoestrogens could increase cancer risk in rats. But a breast cancer researcher, Dr. Kellie Bilinski, said that rat have a very different metabolism from humans. Thus we could not directly apply the results of these studies to humans.

Soybeans contain many isoflavones phytoestrogens in the form of genestein and daidzein in large quantities. Soybeans and its products, i.e. tofu, tempeh, soy milk, soy sauce, etc are sources of calcium and protein, especially for vegetarians and people with lactose intolerance who normally consume soy milk.

According to Professor Ian Olver from the Cancer Council of Australia, if there are side effects of phytoestrogens on tumors that are sensitive to hormones, the soybeans must be in high concentrations. Much higher than what is found in food. There is no problem if soy-based foods are served in a moderate amount. Natural phytoestrogens contain antioxidants so they must be consumed more. It is better not to focus only on the effect of food on one disease. Because, these foods can be beneficial for the prevention and cure of other diseases.

The Australian Cancer Council organization even encourages people to consume soy-based foods as part of a varied and nutritious diet, although scientific evidence of the effect of soy in preventing cancer is uncertain.

There are no human studies showed that soy consumption could be dangerous. Even research on Asian women found that phytoestrogens actually had the effect of protecting the body from breast cancer. The proof, Asian women have lower rates of breast cancer. While in the West, they don't consume that much soy. Soy is thought to help protect body cells from estrogen produced by the body itself.

In addition to breast cancer, several studies also mentioned that soy could reduce the cancer risk of pharynx, esophagus, stomach, pancreas, intestine, and  endometrium (in perimenopausal and postmenopausal women) and also prostate. However, according to the Australian Cancer Council, the evidence is not enough to draw conclusions. Thus further research needs to be done in depth about this.