The term phytoestrogen refers to a naturally occurring compound found in commonly consumed foods that is structurally similar to estrogen. The highest amount of phytoestrogens are found in soy based foods and flaxseed, but are also found in fruits, vegetables, nuts and grains.
Friend or Foe?
Phytoestrogens have a bad reputation. They are often referred to as having “estrogenic” activities, implying they act the same way as our own naturally occurring estrogen. In the oncology world, patients are warned to stay away from phytoestrogens, such as soy and flax, because they mimic estrogen and would therefore be particularly harmful to a woman with breast cancer. However, a very simple review of the published medical literature reveals an entirely different story.
As a naturopathic doctor who focuses on nothing but integrative cancer care, it is my number one priority to be up-to-date and well-read on anything dietary that could be harmful to a person with cancer. There are many health benefits to consuming a diet rich in phytoestrogens, so allow me to present the research below.
How do Phytoestrogens Work?
There is a concept you should know. On cells, there are two kinds of estrogen receptors – one is called “alpha” and one is called “beta”. The alpha receptor is found mainly in the breast, uterus, ovary and bone, while the beta receptor is mainly found in the prostate, bladder, colon, adipose tissue, nervous system and immune system (1). The alpha receptor is mostly responsible for abnormal cell growth associated with breast cancer, and the beta receptor is known to counteract those effects (2).
Natural estrogen binds to each of these receptors with equal strength, however, phytoestrogens are about 20x more selective to the beta receptor than the alpha receptor (3). Phytoestrogens can also displace regular estrogen from receptors. Due to these mechanisms, phytoestrogens are recognized as anti-estrogenic and protective against cancer (4).
Health Benefits of Phytoestrogens
SOY
There are numerous types of phytoestrogens, so let’s start with one of the most well-known – soy. The medicinal ingredient in soy is called genistein, which gets metabolized to other phytoestrogens, such as equol. There have been many animal studies that consistently show genistein does not increase rates of cancer, but decreases the growth of cancer cells (5). A recent large epidemiological study looked at 18 published articles that found that women with a history of breast cancer who ate a diet rich in phytoestrogens had a decreased risk of recurrence (6).
Genistein has also been shown to decrease the incidence of cardiovascular disease (7), increase bone density (8), decrease the formation of fat tissue (9), and have anti-depressant properties (10), all of which are important to address in women with breast cancer.
A diet rich in soy has also been found to be beneficial in men with prostate cancer. One Japanese study found decreased rates of prostate cancer in men who consumed the highest amount of soy (11). Another study in men who had already been diagnosed with prostate cancer found that those who consumed the highest amounts of soy had a decreased risk of metastasis (12). Genistein has been found to increase the expression of several genes that prevent metastasis (13).
Soy and its phytoestrogens have been found to prevent the formation and recurrence of colon adenomas, and therefore may be preventative of colon cancer (14). The same can be said with lung cancer. In a large case-control study of over 24,000 women, it was found there was an inverse relationship between high soy consumption and risk of lung cancer (15).
FLAX
Flax is another medicinal food high in a chemical compound called lignans. A study of post-menopausal women with breast cancer found that high flax intake was associated with not only lower breast cancer-related mortality, but also all-cause mortality (16). In women with no history of breast cancer, eating a diet high in flax was found to decrease the risk of being diagnosed with breast cancer (17). Flax has been shown to reduce markers of inflammation, such as C-reactive protein, which could be one of the mechanisms it helps to reduce the risk of cancer (18).
ENTEROLACTONES
These lesser-known phytoestrogens are found in grains such as barley, rye and wheat, and are also found in seeds, nuts and vegetables. A recent large meta-analysis reviewed about 30 epidemiological studies, and found that there is a protective role of consuming a diet high in these phytoestrogens. Therefore, they may reduce the risk of developing breast cancer, prostate cancer, colon cancer, stomach cancer and lung cancer (19).
BLACK COHOSH
This is a great herb for reducing symptoms of menopause, mainly hot flashes. It can be safely used to reduce the side effects of hormonal medication used for breast cancer. A study of 85 women with breast cancer took placebo or black cohosh, and the results showed that black cohosh reduced symptoms of menopause and did not affect estrogen levels (20). A large German study found that women with a history of breast cancer who took black cohosh regularly had a 4.5 year longer recurrence-free survival, again, showing a protective effect of phytoestrogens (21).
Conclusions
As a doctor so passionate about integrative cancer care, nothing is more frustrating than misinformation. It is very clear from the widely available published research that there are many health benefits to phytoestrogens, especially when it comes to cancer. A patient should feel confident that eating foods rich in phytoestrogens may help to decrease recurrence rates and even slow cancer growth. Talk to me today about a personalized nutrition plan to optimize your health.
- Steroids, 2014;0:13-29.
- Pharmacol Rev, 2006;58(4):773-781.
- Cancer Chemother Pharmacol, 2019;84(3):591.
- Climacteric, 2011;14(2):204-211.
- Molecules, 2019;24(21):3892.
- Bull Cancer, 2020;107(1):61-71.
- J Clin Endocrinol Metab, 2007;92(8):3068-75.
- Ann Intern Med, 2007;146(12):839-47.
- J Clin Endocrinol Metab, 2013;98(8):3366-74.
- Adv Pharmacol Sci, 2015;164943.
- Int Urol Nephrol, 2015;47(6):965-70.
- Nutrients, 2018;10(1):
- PLoS One, 2019;14(3):e0214078.
- World J Gastroenterol, 2013;19(27):4325-331.
- Cancer Epidemiol Biomarkers Prev, 2011;20(3):419-27.
- Breast Cancer Res Treat, 2010;122:229.
- Br J Cancer, 2008;98:636-640.
- Cancer Causes Control, 2014;25:395-403.
- Eur J Pharmacol, 2019;852:107-124.
- J Ethnopharmacol, 2019;238:111840.
- Wien Med Wochenschr, 2017;167(7):147-159.
