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Soy phytoestrogens for clinical nutritionists and CNS candidates

Watch the full video on phytoestrogens here!

Are phytoestrogens bad for you?  Good for you?  These are common questions.  Let’s dive in.

Myth or Truth?  It is best to avoid phytoestrogens 

Myth! You can avoid phytoestrogens if you eat a carnivore diet, only meat, which is fairly unsustainable long term.  But essentially it is nearly impossible to avoid them.  Phytoestrogens are abundant in plant foods – seeds, grains, beans, fruits and vegetables.  Anyone heard of resveratrol? or quercetin?  These are common flavonoids that have phytoestrogen properties and are found throughout the plant kingdom.  I love this table from Ruth Trickey’s book Women Hormone and the Menstrual Cycle for a resource on sources of phytoestrogens.  







Steroidal saponins

Flavones (Luteolin etc)





Whole grains




Red clover

Alfalfa sprouts













Wild yam













Myth or Truth?  Phytoestrogens are harmful

Myth.  Phytoestrogens are a variety of plant compounds that weakly bind to estrogen receptors.  And not all estrogen receptors are the same.  Estrogen alpha receptors are involved in tissue proliferation in the uterus and breast.  Estrogen beta receptors are more involved in immune and neurological health and counter the effect of the alpha receptor.  

Plant compounds are not a perfect lock and key fit to the estrogen receptor like estradiol, so the effect is weaker.  I like to use the analogy of a high school basketball player versus Kobe Bryant.  Kobe is estradiol and the high schooler is the lignan or flavonoid.  Kobe is going to get the ball in the hoop much ore often than the high school basketball player.

If you focus on eating whole foods and mostly plants, then you will eat foods that are good for estrogen levels.   Foods can do this by modifying detox pathways for estrogen, improving gut clearance, or mimicking the action of estrogen in a deficiency state.  Take for instance, cruciferous veggies (aka broccoli, cauliflower, kale, radish, kohlrabi etc), the compounds DIM and I3C in the broccoli family of veggies improve the metabolism of estrogen favorable to cancer prevention.  These same cruciferous veggies contain lignans a phytoestrogen which can bind to Estrogen beta receptors and improve symptoms in perimenopausal and postmenopausal women.  

Myth or Truth?  Soy is harmful

Both, read on.   There is a lot of fear of soy and the main active compound isoflavones.  There have been some a handful negative animal studies on soy for hormone-dependent cancers but this has not been replicated in humans.  Cancer protective effects are seen in cultures that consume soy from an early age, in whole food forms, tempeh, tofu, edamame.  Soy isoflavones are arguably the most powerful of all the phytoestrogens.  Super large amounts of soy can suppress thyroid function.  Also, soy is commonly genetically modified so it is best to get organic. 

Most hormone-dependent cancers predominantly exhibit alpha receptors, but some later stage cancers express beta and alpha receptors equally, so we do need to be aware of that!  As the most potent source of isoflavones, this is why soy is generally avoided in later stage breast cancers.  Early-stage breast cancer responds well to dietary phytoestrogens.  

Also, keep in mind that the hormonal effects are one small part of the story of isoflavones.  These phytochemical in soy have many health benefits including improving cancer cell death, reducing DNA damage, supporting the immune system and reducing oxidative stress.  

Myth or Truth?  Your microbiome affects the bioavailability of phytoestrogens 

Truth – These compounds are mostly inactive when consumed and are activated by enzymes and the gut microbiome.  These secondary metabolites are stronger than their parent compounds.

Myth or Truth?  Eating phytoestrogen rich foods can improve hot flashes

Truth – Try it yourself and see.  As an example, a client once told me that drinking carrot juice reduced her hot flashes.  In an estrogen deficiency situation like post menopause, eating foods rich in phytoestrogens can help to reduce symptoms. There is a lot of variability person to person.  You will have to try it out and see.

Remove barriers for consuming phytoestrogens, i.e. if someone has trouble digesting beans, soak or sprout them.  It does not have to be soy.  You can get phytoestrogens from all kinds of legumes and plant foods.  Reference the table above for inspiration.

You can find Rebecca teaching about herbal medicine and other topics in our Educational Webinar Group Meetings as a part of our Mentorship Program.  Our functional nutrition training provides nutrition research and evidence-based nutrition practice.  We review nutrition practices for specialized populations, disease states, as well as highlight on laboratory analysis and herbal medicine. We bring in a diverse array of guest speakers in our monthly educational webinars!

Book a Strategy Call with Rebecca to learn more about personalized mentorship for nutrition students and nutrition graduates.

Bernatoniene J, Kazlauskaite JA, Kopustinskiene DM. Pleiotropic Effects of Isoflavones in Inflammation and Chronic Degenerative Diseases. Int J Mol Sci. 2021 May 26;22(11):5656. doi: 10.3390/ijms22115656. PMID: 34073381; PMCID: PMC8197878.

Cimmino A, Fasciglione GF, Gioia M, Marini S, Ciaccio C. Multi-Anticancer Activities of Phytoestrogens in Human Osteosarcoma. Int J Mol Sci. 2023 Aug 28;24(17):13344. doi: 10.3390/ijms241713344. PMID: 37686148; PMCID: PMC10487502.

Chen X, Uzuner U, Li M, Shi W, Yuan JS, Dai SY. Phytoestrogens and Mycoestrogens Induce Signature Structure Dynamics Changes on Estrogen Receptor α. Int J Environ Res Public Health. 2016 Aug 31;13(9):869. doi: 10.3390/ijerph13090869. PMID: 27589781; PMCID: PMC5036702.

Hughes CL Jr. Phytochemical mimicry of reproductive hormones and modulation of herbivore fertility by phytoestrogens. Environ Health Perspect. 1988 Jun;78:171-4. doi: 10.1289/ehp.8878171. PMID: 3203635; PMCID: PMC1474615.

Trickey, Ruth. Women, Hormones & The Menstrual Cycle; Herbal & Medical Solutions From Adolescence to Menopause. St. Leonards NSW 2065 Australia: Allen & Unwen. 1998. pp. 263, 313, 315, 325.


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