It loves me, it loves me not... Are phytoestrogens (plant oestrogens) good for women's health? And for endometriosis?
- Helena Torres
- Jan 7
- 10 min read
Updated: Jan 9
If you have an oestrogen-dependant disease then you should eliminate it from your diet, right? WRONG! Our body is much more complex than that… Or should I say, wiser?
There are essentially three types of oestrogen:
oestrogen produced by your body
xenoestrogen (xeno = new) which is present in man-made substances that enter your body through diet, medicines, hygiene products and thousands of other things you come into contact with. These substances are similar to oestrogen and act within you as oestrogen and endocrine disruptors
And phytoestrogens, which come from substances contained in plants and which, when synthesised by our body, resemble oestrogen and enhance or go against its effect (antagonists).
Phytoestrogens are found in a variety of fruits, vegetables, sprouts, beans, seeds, tea… Their anti-inflammatory, anti-oxidant, anti-proligferative, anti-angiogenic (fighting the growth of tumours and the blood vessels that nourish them) and pro-apoptotic (helping cells die when they should) properties are well known and studied. In other words, it is more than proven that they are beneficial to our health, if organic and non-GMO. On the other hand, you would have to avoid eating fruits, vegetables and cereals altogether to avoid phytoestrogen intake whatsoever [1]! But even so, the question of whether phytoestrogens are dangerous or beneficial due to their similar role to estrogens arises.
Poor soy is actually good after all! Phytoestrogens and cancer
It is very common in Portugal to hear reports of women with breast cancer who have been advised by doctors not to consume soy and its derivatives. Which poses a question for those who have diseases like endo, related to oestrogen dominance. There is a lot of misinformation and noise blaming the poor soy!
Here’s what I found in my research:
A meta-analysis of 52 studies conducted up to October 2023 on soy consumption found that
Higher consumption of soy products (fermented or not) tofu and soy milk are associated with a lower risk of cancer
Increasing soy product consumption by 54g per day reduces cancer risk by 11%
Increasing tofu consumption by 61g per day reduces cancer risk by 12%
Increasing soy milk consumption by 23g per day reduces cancer risk by 28% [2].
Another study of 300.000 women in China looked at their soy consumption and reported breast cancer incidence. Results showed that moderate soy consumption did not increase the risk of breast cancer. A meta-analysis of prospective studies estimates that for every 10 mg/day increase in soy isoflavones, there was a 3% decrease in breast cancer risk. [3].
Since at least 2016, researchers have been reporting that higher soy consumption amongst Asian women is associated with approximately a 30% lower risk of developing breast cancer, particularly if that consumption occurs in childhood/adolescence. They reiterate that concerns about regular soy consumption and breast cancer risk are unfounded. [4].
Soy consumption will have different effects depending on each person's baseline hormonal level, i.e., teenagers, pregnant women, post-menopausal women... [5], as we will also see in the point regarding endometriosis.
Soy and its derivatives do not increase the risk of incidence nor recurrence of breast cancer. On the contrary, they reduce the risk of breast cancer. [6].
Phytoestrogens and menopause
Nowadays, it is very common for alternative therapists to recommend supplementation with phytoestrogens, namely soy isoflavones, to avoid osteoporosis and adverse symptoms of menopause.
Studies on soy isoflavones supplements report different outputs: beneficial, null or even adverse effects, leading to uterine bleeding. The difference lies in the big question that seems to be the dosage and duration of this supplementation. [5].
In 2015 the European Food Safety Authority assed the potential risks of isoflavone supplementation (soy is rich in this phytoestrogen) for the health of peri- and post-menopausal women. Based on the reviewed studies carried out with women, there is no evidence of any problems with thyroid hormones, uterine thickening or breast cancer risk for typical doses of menopause supplements that vary between 35-150mg/day.
Taking into account that the average European consumption was less than 1mg/day of isoflavones vs. the Asian consumption that we saw in the previous point, there is no problem at all, quite the opposite, it is recommended that all women eat a tofu burger [7].
Diet vs supplements
But it is one thing to include soy in your diet and quite another to include soy products in each meal and take isoflavone supplements on top of that…! For example, a 200g tofu burger already has 54.3mg of phytoestrogens (table 1), that is, one third of the maximum typical value in most supplements and enough to make all the difference and reduce the risk of cancer. In the case of soy in particular, what concerns the most is that much of it is transgenic and loaded with pesticides. These are the two factors that should worry us all!
Food | Phytoestrogens per 100g of food |
Flax seeds | 379.38mg |
Soy grains | 103.92mg |
Tofu | 27.151mg |
Soy iogurt | 10.275mg |
Sesame seeds | 8.008mg |
Flax seed bread | 7.54mg |
Multi cereals bread | 4.799mg |
Soy drink | 2.958mg |
Humus | 0.993mg |
Garlic | 0.604mg |
Table 1: Quantity of phytoestrogens per 100g of food [1]
Phytoestrogens are beneficial for endometriosis
In 2021, a systematic review of 60 scientific studies was carried out on the role of phytoestrogens in endometriosis. The studies include in vitro, in vivo tests with animals and with humans.
The results of the vast majority of studies with phytoestrogen supplements indicate that the consumption of phytoestrogens has beneficial results in the fight against endometriosis!
However, for now, only resveratrol has been shown to be successful for endometriosis in humans, on supplements of 400mg twice a day for 12-14 weeks [8][9]. In addition, resveratrol has beneficial on cancer, including liver, colorectal, breast, among others. Its effects are beneficial in the initiation, promotion and progression of tumours [10]. It is worth remembering that endometriosis shares several characteristics with cancer, although it is not cancer. Resveratrol also helps to reduce total cholesterol [11]. We have already seen that liver cirrhosis can lead to endometriosis in men by transforming androgens into oestrogens.
Hence, the answer is: it is good to eat foods with phytoestrogens!
In simple terms, what seems to happen is that in an environment with low estrogen, such as in menopausal women, phytoestrogens attach to estrogen receptors more easily and mimic estrogen.
In environments with excess estrogen, particularly E2, estradiol, which is what we mainly want to reduce, when phytoestrogens win the fight for the estrogen receptor, they act in a similar way to estradiol, but with one big difference. Phytoestrogens have much lower activation of a gene transcription factor, that is, activation of genes that we do not want and alteration of our epigenetics.
Attention! More than 1g of resveratrol supplementation has undesirable effects such as nausea, diarrhea or abdominal pain. [10].
nonetheless, mind the following:
Only resveratrol supplementation has been tested on humans so far
In high doses, such as in dietary supplements, soy isoflavones can thicken the endometrium. Soy and its derivatives are the foods that contain the most isoflavones.
Our digestive system is different from that of laboratory mice! Our ability to assimilate phytoestrogens can be impacted by gender, intestinal transit time and our intestinal flora (quantity and type of bacteria in our intestines) [8][9].
Suggestions for your diet
Suggestion 1: Include the top different phytoestrogens in your diet
There are several types of phytoestrogens: stilbenes, such as resveratrol; flavonoids (puerarin, genistein, coumestrol, epicatechin, naringenin, etc.) or lignans, such as enterolactone. Since the concentration of each substance makes all the difference, here is a table I compiled of the top foods by substance:
Substance | Foods rich in the substance | Substance nutritional value |
Resveratrol | Sorrel root [12] | 32-1535 µg/g |
Itadori tea (Polygonum cuspidatum, polygonum japonicum or Japanese Knotweed) [13] | 297-377 µg/g | |
Spanish red wine | 1.92-12.59 mg/l | |
Spanish black grape juice | 1.14-8.69 mg/l | |
Puerarin | Kuzu or kudzu root (Pueraria lobata) [Note A] | |
Genistein | Soy and soy products | |
Coumestrol | Soy, spinach, Brussels sprouts… | |
Epicatechins [14] | Cocoa beans | 99.2 mg/100g |
Dark chocolate | 41.5 mg/100g | |
Broad beans | 29.1 mg/100g | |
Green tea | 8.3 mg/100g | |
Nariguenina | Citric fruits and rosemary | |
Lignans | Flax seeds (and other high-fiber seeds) [15] | 301 mg/100 g |
Table 2 - Top foods by phytoestrogen group
[Note A] Pueraria lobata is a climbing plant of the legume family that is widely used in traditional Chinese medicine. It is frequently used in the treatment of numerous diseases, including endometriosis, for its pharmacological properties such as vasodilation, cardioprotection, neuroprotection, antioxidant, anticancer, anti-inflammatory, pain relief, promotion of bone formation, inhibition of alcohol intake and attenuation of insulin resistance [16].
Suggestion 2. Consider resveratrol supplements
As already stated, it has been successfully tested for endometriosis in humans up to a dose of 400mg twice a day for 12-14 weeks. Results include decreased menstrual and pelvic pain, decreased aromatase (the transformation of androgen cells into estrogens and their biosynthesis in the body), decreased expression of genes we don’t want…[5].
Supplements or... A glass of red wine a day, keeps the doctor away!
Studies indicate that alcohol consumption is bad for our health, but they fail to differentiate between excessive consumption of vodka and a small amount of wine with a meal.
I would almost say that wine is not alcohol, it is medicine from the Gods! And Bacu was not only the God of Wine, but also fertility and revelry, and a patient with endometriosis needs all of that!
Popular wisdom tells us about the benefits of a glass of wine, considered the nectar of youth by the elderly among us. [17]. Science has called it “The French Paradox”: how can a culture that consumes so much saturated fat in its delicious cheeses and croissants have good cholesterol levels? The explanation given was the consumption of wine, particularly very dark red wine, which lowers cholesterol. [18]. Red wine (the darker the better) is rich in resveratrol. So, in moderation and unless it makes you feel unwell, why not have an organic Pinot Noir?
You might ask, why not simply make your diet richer in resveratrol instead of supplements or red wine? Of course, that’s a suggestion too. However, the amount of food you would have to eat to get 1g of resveratrol, which would be a therapeutic dose, is absurd.
At the end of the day, human metabolism is holistic. No scientific study can truly isolate one variable. If you eat more foods rich in resveratrol, they are also rich in many other substances and the combined effect is impossible to measure, but we know it is very positive!
Suggestion 3: Consume resveratrol with turmeric to increase bioavailability [13]
We are not what we eat, but rather what our body is able to assimilate!
The human body assimilates resveratrol better with turmeric. In other words, there's nothing like a glass of dark red wine with a curry!
! Attention !
My golden rule is an organic, moderate and varied diet. Organic is not only without pesticides, but also foods that are not packed or preserved in plastic, for example. Moderation means not overeating anything and being careful about the dangers of consuming food supplements in doses that have not been studied or discussed with your doctor. Variety means including as many beneficial foods as possible in your diet.
Endo is not linear. You should always consult your doctor about what is best for you. You should also be aware of other symptoms you experience with certain foods, especially if you suffer from Irritable Bowel Syndrome or other gastrointestinal symptoms as a result of endo.
Finally, you should be very careful about the potentially adverse effects of consuming phytoestrogens for those who live in areas with low iodine or suffer from hypothyroidism [5].
References:
[1] Leal, K., & Leal, K. (2024, January 26). 37 alimentos ricos em fitoestrogênios (e seus benefícios). Tua Saúde. https://www.tuasaude.com/alimentos-ricos-em-estrogenios/
[2] Wang, C., Ding, K., Xie, X., Zhou, J., Liu, P., Wang, S., Fang, T., Xu, G., Tang, C., & Hong, H. (2024). Soy product Consumption and the Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients, 16(7), 986. https://doi.org/10.3390/nu16070986
[3] Wei, Y., Lv, J., Guo, Y., Bian, Z., Gao, M., Du, H., Yang, L., Chen, Y., Zhang, X., Wang, T., Chen, J., Chen, Z., Yu, C., Huo, D., & Li, L. (2019). Soy intake and breast cancer risk: a prospective study of 300,000 Chinese women and a dose–response meta-analysis. European Journal of Epidemiology, 35(6), 567–578. https://doi.org/10.1007/s10654-019-00585-4
[4] Messina, M. (2016). Impact of soy foods on the development of breast cancer and the prognosis of breast cancer patients. Complementary Medicine Research, 23(2), 75–80. https://doi.org/10.1159/000444735
[5] Domínguez-López, I., Yago-Aragón, M., Salas-Huetos, A., Tresserra-Rimbau, A., & Hurtado-Barroso, S. (2020). Effects of Dietary Phytoestrogens on Hormones throughout a Human Lifespan: A Review. Nutrients, 12(8), 2456. https://doi.org/10.3390/nu12082456
[6] DePolo, J. (2024, July 18). Soy and Breast Cancer. https://www.breastcancer.org/managing-life/diet-nutrition/breast-cancer-risk-reduction/foods/soy
[7] European Food Safety Authority. (2015, October 21). Safety of isoflavones from food supplements in menopausal women. https://www.efsa.europa.eu/en/efsajournal/pub/4246
[8] Cai, X., Liu, M., Zhang, B., Zhao, S., & Jiang, S. (2021). Phytoestrogens for the management of endometriosis: findings and issues. Pharmaceuticals, 14(6), 569. https://doi.org/10.3390/ph14060569
[9] Aydin, N. E. (2021, November 25). Phytoestrogens could have promising effects in endometriosis management. EndoNews.com: News & Research Portal for Endometriosis Foundation of America. https://www.endonews.com/phytoestrogens-could-have-promising-effects-in-endometriosis-management
[10] Ko, J., Sethi, G., Um, J., Shanmugam, M. K., Arfuso, F., Kumar, A. P., Bishayee, A., & Ahn, K. S. (2017). The role of resveratrol in cancer therapy. International Journal of Molecular Sciences, 18(12), 2589. https://doi.org/10.3390/ijms18122589
[11] Cao, X., Liao, W., Xia, H., Wang, S., & Sun, G. (2022). The effect of resveratrol on blood lipid profile: A Dose-Response Meta-Analysis of Randomized Controlled trials. Nutrients, 14(18), 3755. https://doi.org/10.3390/nu14183755
[12] Grupo testa medicamento inspirado no vinho tinto. (2008, July 30). Folha De S.Paulo. Retrieved on January 5, 2025 em http://www1.folha.uol.com.br/ciencia/2008/07/427618-grupo-testa-medicamento-inspirado-no-vinho-tinto.shtml
[13] Gupta, C. G. C., Sharma, G. S. G., & Chan, D. (2014). Resveratrol: a chemo-preventative agent with diverse applications. In CABI eBooks (pp. 47–60). https://doi.org/10.1079/9781780643632.0047
[14] Nutrition & Health info Sheets for health professionals - Catechins and Epicatechins. (2020, December 5). UC Davis Nutrition Department. https://nutrition.ucdavis.edu/outreach/nutr-health-info-sheets/pro-catechins
[15] Soleymani, S., Habtemariam, S., Rahimi, R., & Nabavi, S. M. (2020). The what and who of dietary lignans in human health: Special focus on prooxidant and antioxidant effects. Trends in Food Science & Technology, 106, 382–390. https://doi.org/10.1016/j.tifs.2020.10.015
[16] Zhou, Y., Zhang, H., & Peng, C. (2013). Puerarin: A Review of Pharmacological Effects. Phytotherapy Research, 28(7), 961–975. https://doi.org/10.1002/ptr.5083
[17] Live to 100, the Secrets of the Blue Zones, Author Dan Buettner, Netflix Documentary
[18] Weiskirchen, S., & Weiskirchen, R. (2016). Resveratrol: How much wine do you have to drink to stay healthy? Advances in Nutrition, 7(4), 706–718. https://doi.org/10.3945/an.115.011627