My research into phytoestrogens and how they affect hormones started many many years ago and the very beginning of my health journey over ten years ago. At that stage, I had a little concern over soy products because I had heard so much negativity around them, but after a quick look at the research, it became irrefutably clear to me that soy foods (especially the whole organic versions, not processed or GMO) are incredibly healthy with many health benefits. They can be used as a wonderful tool to help women balance their hormones. It is strange to me that over ten years later, there is still so much negative attention given to phytoestrogens, especially since the evidence has become even more conclusive over the years.
What are phytoestrogens?
Phytoestrogens are chemical compounds found in nearly all plant foods in varying amounts. They have a chemical structure similar to estrogen and have been shown to be able to weakly bind to estrogen receptors in the body. There are two main classes of phytoestrogens: isoflavones and lignans. Isoflavanes are the most potent type and are found mainly in soy (this is why so much phytoestrogen research is based on soy) and other legumes like chickpeas and peanuts as well as some fruits. Lignans are found in seeds, whole grains, and fruit, and other legumes. There are also some lesser-known phytoestrogens like coumestans and stilbenes found in cruciferous vegetables and a few other plant foods.
Why are phytoestrogens considered a problem for women’s hormones?
Since the discovery of phytoestrogens and their ability to bind to estrogen receptors, the natural assumption has been that they can increase estrogen in the body. Excess estrogen in the body is a problem because it can create a few hormone imbalances but more importantly, it has been identified as a leading cause of breast cancer and other female cancers. Based on these assumptions, it is easy to see why phytoestrogens would get a bad wrap, however, there have been many studies conducted since to test if this theory is true and based on my research, the evidence seems to point in a different direction. Note: just because phytoestrogens have estrogen-like properties and are capable of weakly binding to estrogen receptors does not make them real estrogen. Phytoestrogens are not the same as the estrogen produced by our bodies, or the same as the estrogen ingested when eating animal foods. The level of estrogen in animal foods is significantly less than the phytoestrogen content in food however animal foods contain real mammalian estrogen which is by and large identical to human estrogen and has been shown to lead to excess estrogen in the body. In fact, dairy contains about 60% of all the real estrogen consumed. Animal products and animal fats have been strongly linked to estrogen excess in women and men (and other hormone imbalances) and also linked to resulting diseases such as breast cancer. It should be noted that phytoestrogens, when consumed in whole food form, have not been shown to have this effect.
What does the evidence actually say about phytoestrogens and women’s hormones?
- It has become clear from the research that phytoestrogens have both an estrogenic and anti-estrogenic effect, meaning they can raise or lower estrogen in the body.
- Phytoestrogens have been shown to help reduce hot flashes in menopausal women.
- Phytoestrogens can help to reduce period pain because the foods that contain phytoestrogens are generally anti-inflammatory.
- Phytoestrogens can help with heavy periods by lowering estrogen if needed
- Phytoestrogens (especially in soy) have been found to be very beneficial for women with insulin-resistant type Polycystic Ovarian Syndrome (PCOS) and insulin resistance in general
- A 2013 review highlights that studies that show that eating soy (high phytoestrogen) decreases the risk of developing breast cancer, (breast cancer rates in Asian women who eats lots of soy are much lower than western women who eat little soy)
- Other studies show that phytoestrogens have been shown to mildly reduce the risk of breast cancer, the benefits are mainly with high phytoestrogen intake before puberty
- There is evidence that phytoestrogens can have a protective factor for heart disease and osteoporosis
- Although phytoestrogens have been shown to raise low estrogen in menopausal women they are unlikely to help raise estrogen levels for girls suffering from a loss of period due to eating disorder, not eating enough or excessive exercise. This can only be corrected through adequate calorie intake (read my article about how I raised my estrogen here) https://hazelandcacao.com/how-i-raised-my-low-estrogen-levels-naturally/
- The side effects of phytoestrogens generally pertain to women taking phytoestrogen supplements as a more “natural” version of hormone replacement. Eating whole foods that are high in phytoestrogens does not seem to have many negative effects.
The bottom line: phytoestrogens are found in nearly all plant foods in varying amounts so are very difficult to avoid. Eating more plants is generally always a good idea for our health, and our hormones are no exception.
Mourouti N, Panagiotakos DB. 2013) ‘Soy food consumption and breast cancer.’ Maturitas (, http://dx.doi.org/10.1016/j.maturitas.2013.07.006
Messina, M. (2010). ‘A Brief Historical Overview of the Past Two Decades of Soy and Isoflavones Research’. J Nutr 140(7):1350S-1354
SHilakivi-Clarke, L. Andrade, JE. Helferich, W. (2010). ‘Is Soy Consumption Good or Bad for the Breast?’ J Nutr 140(12):2326S-2334
Trock BJ et al. (2006) ‘Meta–analysis of soy intake and breast cancer risk’. J Natl Cancer Inst. 98(7): 459-471.