Are phytoestrogens endocrine disruptors?


What exactly are phytoestrogens?

Technically speaking, phytoestrogens belong to the class of plant molecules known as phytoalexins, which are natural defense molecules made by plants when they’re stressed or under attack by micro-organisms.   The amount of phytoestrogens produced by a plant depends both on its cultivar and also on its growing conditions.  Temperature, rainfall, harvest period, and soil fertility all impact the quantity of phytoestrogens produced by a plant.


These molecules can interact with either of your estrogen receptors, alpha or beta.  Phytoestrogens typically mimic the action of estrogen when bound to these receptors, and they can also alter production of reproductive hormones like progesterone, either increasing or decreasing production of these hormones.  The takeaway here is that phytoestrogens are naturally occurring EDCs.


Phytoestrogens are naturally occurring EDCs


So, why do these molecules behave like estrogen in your body? 


As we talked about in the first episode in this series, estrogen receptors are notoriously promiscuous meaning that a wide variety of naturally occurring compounds like phytoestrogens or a range of synthetic compounds can also bind to them, and when this happens, the xenoestrogen can mimic estrogen’s response with the receptor or it can act in an anti-estrogenic way triggering a different cascade of cellular effects.  Why are your estrogen receptors so promiscuous? 


Well, this is above my pay grade.  My belief is that it’s one of the ways your body connects with nature’s rhythms and one of the ways our bodies are made to interact with the world and nature.  We’ve spent the past few weeks talking about endocrine disruptors, and if you’ve listened to those episodes, you’ve heard me mention more than once my belief that everything in our world, the foods we eat, the drinks we drink, the particular light spectrum at any given time of day, all of these things are endocrine disrupting.  Even minerals, like iodine and magnesium, can influence the creation of hormones within your body, so your diet largely impacts your body’s ability to make hormones, and yes, these minerals along with the other nutrients and ingredients in your diet, are endocrine disrupting. 


The difference between these naturally occurring endocrine disruptors and the slew of synthetic endocrine disruptors is that these compounds have been part of our diets and part of our environment for eons whereas the host of synthetic endocrine disruptors have only been around for 100 to 150 years in most cases.  The other problem with many synthetic endocrine disruptors is that they’re specifically targeting reproductive hormones and/or thyroid hormones, and this is resulting in real health conditions. 


The big question is, do phytoestrogens pose a risk to your health in the same way that these synthetic endocrine disruptors do?  


We’ll build up to that answer, but first, let’s talk about exactly what are phytoestrogens.


Have you heard of polyphenols?  Phytoestrogens belong to the class of molecules known as polyphenols, and most phytoestrogens can be further divided into two categories under the polyphenol umbrella:  either flavonoids or lignans.


Flavonoids are the largest group of plant phenols and include over 4000 compounds.  The soy phytoestrogens, genistein and daidzein fall into a subclass of flavonoids, the isoflavonoids.  Genistein has a binding affinity of about a third that of estradiol to ER alpha and about 1/1000th the binding affinity of estradiol to ER beta.  Genistein mimics estradiol in breast, ovarian, endometrial, prostate, vascular, and bone tissue.  We talked about receptor binding affinity and hormone mimicry vs. antagonism in an earlier episode of this series, so if you missed that one, head back and take a listen.


Genistein is also a potent anti-oxidant and also displays anti-inflammatory and anti-carcinogenic properties.


Quercetin and rutin are two other phytoestrogens belonging to the flavonoid family.  Both of these compounds are antioxidants and also anti-inflammatory.


Lignans are yet another group of polyphenols, and flaxseed contains some of the highest levels of phytoestrogenic lignans, specifically, secoisolariciresinol.  Coumestans are another class of polyphenols that can exhibit estrogenic activity, specifically the coumestan, coumestrol.  Clover and soybean sprouts have high levels of coumestrol, and both brussel sprouts and spinach also contain this phytoestrogen though in lower amounts.


Stilbenes are still another class of molecules that contain some phytoestrogens, and resveratrol is likely the best known phytoestrogen in this class of compounds.  Resveratrol is naturally produced by plants in response to injury and also as a way to protect from UV light.  Peanuts, blueberries, and grapes are all sources of resveratrol.


Just a quick recap, phytoestrogens may belong to the molecular class flavonoids, lignans, stilbenes, coumestans, or another class not yet mentioned, chalcones, but not all flavonoids, lignans, stilbenes, coumestans, or chalcones display estrogenic activity.


By far, soy contains more phytoestrogens than any other commonly consumed food with reported levels of genistein between 0.27 and 0.84 grams of genistein per gram dry weight of soy.  Levels of daidzein in soy are reported between 0.11 and 0.56 grams of daidzein per gram dry weight of soy.


The estimated daily intake of isoflavones (again, daidzein and genistein both belong to this class) in the traditional Japanese diet ranges from 15 to 200 milligrams per day resulting in an average blood level concentration of 744 nanomoles phytoestrogens per Liter blood in adult Japanese women.  By comparison, infants in America fed soy-based formula ingest doses have sustained plasma concentrations of phytoestrogens up to 7,000 nanomoles per Liter.  A study in Lancet noted the average daily exposure to phytoestrogens from baby formula is six to eleven times higher than a hormonally active dose in adults.


Breastfed babies on the other hand aren’t exposed to estrogen through their mother’s milk because both estrogen and progesterone production fall after pregnancy and stay low throughout breastfeeding.


The estrogenic activity or binding affinity of genistein and daidzein is on the order of 1,000 to 10,000 times lower than estradiol.  Still, with daily exposure levels of six to eleven times higher than what’s required to be hormonally active in adults, this is noteworthy.


There’s some research that suggests soy also interferes with thyroid hormones, specifically in infants with congenital hypothyroidism who have diets rich in soy.  Specifically, soy seems to exacerbate hypothyroid tendencies, driving TSH levels higher.  A 2018 review of the literature found no clinically significant effects in soy consumption and thyroid function of healthy adults.


Switching from soy to a few other phytoestrogens, let’s talk about how these naturally occurring compounds can impact your menstrual cycle. 


I mentioned seed cycling a few episodes ago, and the premise of seed cycling is to eat 1 Tbsp. of flax seeds and 1 Tbsp. of pumpkin seeds daily for the first half of your cycle (basically, the day you start your period until the day you ovulate) and then switch to 1 Tbsp. of sesame seeds and 1 Tbsp. of sunflower seeds daily for the second half of your cycle (until you start your next period).  An easy way to remember this is PFF and SSS, which is pumpkin & flax for the first half and sesame and sunflower for the second half.


Why these particular seeds?  Flax seed contains a couple of lignans that are estrogenic.  In a study published in the Journal of Clinical Endocrinology & Metabolism way back in 1993, a group of researchers conducted a study in 18 normally cycling women. 

Each woman ate her normal diet for 3 cycles and took her usual dietary supplements.  For another 3 cycles, she incorporated flax seed into her diet for her full cycle duration.  For this particular study, data wasn’t collected during the 1st cycle either during the control arm or during the flax seed supplementation arm to serve as a washout period because this was a well-designed cross-over study. 


What the researchers found during the 2nd and 3rd cycles supplemented with flax seed was that the luteal phase was significantly longer by just over a day.  The researchers also found that no anovulatory cycles occurred when the women supplemented with flax seed compared with 3 anovulatory cycles during the control months without flaxseed supplementation. 


For this study, there weren’t any significant differences in estradiol or estrone concentrations throughout her cycle regardless of whether the women were supplementing with flaxseed or not. 

And, flaxseed supplementation had no significant effect on progesterone concentrations during the luteal phase although ratios of progesterone to estradiol were significantly higher during the flaxseed supplemented cycles.  And, flaxseed supplementation also had a slight effect on testosterone levels. 

Even though testosterone levels weren’t significantly higher when the women supplemented with flaxseed, there was a slight increase in testosterone levels around mid-cycle when our testosterone levels spike.

This is an example of how these phytoestrogens work.  Despite binding to estrogen receptors, they're impacting your body in very different ways than your endogenous estrogen hormones.

One more important note, some common foods, like green tea, which contain a couple of phytoestrogens in the lignan family also generally display anti-estrogenic effects. 


We’re spending an entire episode on tea next with The Tea Spot founder and author of Cancer Hates Tea, Maria Uspenski.


Continuing with this duality discussion, let’s talk about resveratrol for a minute.


Even though resveratrol is a phytoestrogen, it’s been found to increase progesterone production and also decreases cortisol production.


Resveratrol displays anti-inflammatory properties and is also an incredibly powerful antioxidant because it increases nitric oxide production in your body, which is one of the hypothesis on why it’s so beneficial for combatting non-estrogen dependent cancer cells.  At low doses, resveratrol is cardioprotective, activating nitric oxide production, creating a stable redox environment… this is something we haven’t talked about yet on the podcast because it’s kind of deep and involves seeing the world in balance rather than in black and white. 


In short, an antioxidant can become a pro-oxidant once it’s oxidized, and a stable redox environment is when antioxidants in their oxidized state, which happens when they’re spent after they’ve soaked up the free radical or the reactive oxygen species and are no longer capable of soaking up more free radicals or reactive oxygen species and are now able to act as pro-oxidants, which means they’ve become the energetic molecules that can cause damage. 

When these oxidized antioxidants are reduced from this pro-oxidant state back into their active antioxidant state and there’s a good balance between the rate of reduction (antioxidant rejuvenation or antioxidant resurrection) and their oxidized state so that the oxidized state or pro-oxidant form doesn’t hang around long enough to cause damage, this is a stable redox environment.


Resveratrol promotes a stable redox environment by helping maintain levels of several key antioxidant enzymes responsible for resurrecting glutathione in your body.  Glutathione, of course, is an important antioxidant produced inside your body.


Again, at low doses, resveratrol has been shown to promote a stable redox environment, acts as a powerful anti-inflammatory ingredient, reduces platelet aggregation, and even reduces myocardial infarct size.  At higher doses however, resveratrol depresses cardiac function and results in an unstable redox environment and increases myocardial infarct size.  While resveratrol has been found helpful for outcomes in non-estrogen dependent cancers, it can act as a superagonist in estrogen-dependent breast cancers.  Resveratrol is also helpful in resolving PCOS and has demonstrated improvement in women with endometriosis.


And, resveratrol isn’t alone among naturally occurring phytoestrogens in this duality.


Despite their estrogenic activity, many studies show that phytoestrogens are beneficial for either preventing cancer or in improving outcomes in those diagnosed with cancer.  Why is this?  Many phytoestrogens display anti-inflammatory properties in addition to their estrogenic properties.  Genetics also play a huge role as studies often contradict each other based on whether women of African, Caucasian, or Asian descent are studied.


Phytoestrogen concentrations also plays a role in whether these compounds promote cancer growth or inhibit cancer growth.  In other words, while a blanket statement can be made regarding synthetic endocrine disruptors like phthalates and PCBs that these chemicals are not beneficial to your health, for phytoestrogens, the answer is much more individualistic and much more nuanced.


And, this begs the question why isn’t nutrition held in the highest regard for women and men who have been diagnosed with or are prone to hormonal dependent cancers?  In my own limited experience with people who have overcome cancer, nutrition isn’t discussed as part of their therapy and prevention from recurrence and yet, there’s so much scientific interest in this area as witnessed by the large volume of peer reviewed and published research in this area and also by the ever growing supplements market.


And, this also highlights something extremely important and something uncomfortable for us as mere mortals to grasp.  Balance is key.  Just like the hormones in your body that communicate with each other to upregulate and downregulate production of other hormones in a beautiful symphony, it’s important to maintain that same type of balance in your diet.  If you’re genetically predispositioned to a hormone-dependent cancer, it’s even more important to research for yourself and your genetic predisposition and your race to make your own informed choice about restricting certain foods from your diet, and yes, this is a tall order, and it feels right to state my disclaimer here that I’m not a doctor or qualified medical professional and am not offering therapeutic advice.  The information provided in this podcast is for educational purposes only and does not substitute for sound medical advice.


We’ve spent so much time over the past few episodes pretty deep in the science of things, and next time we’re taking a bit of a reprieve from the science to talk with Maria Uspenski about tea.  That conversation is the intro and segue into a wellness series, and the reason for this is because your skin’s appearance and your skin’s health are tied into your mental & emotional wellness just as much as it’s tied into your physical wellness.  I hope you’ll join me for 3 great interviews in this series.


Would you take a quick second to share this podcast with a friend?  If you’re listening on iTunes, it would mean the world to me for you to take a minute and leave a review as well.


Thank you so much for your time.


Until next time,


Phytoestrogens: food or drug?

Soy based infant formula are phytoestrogens still in doubt

[14796805 - Journal of Endocrinology] Effects of genistein, resveratrol, and quercetin on steroidogenesis and proliferation of MA-10 mouse Leydig tumor cells,ER)%20subtypes%20ERalpha%20and%20ERbeta.


Brandy Searcy founder Rain Organica

About the Author

Brandy's a formulation scientist and self-proclaimed health geek who loves hiking, gardening, bird-watching, and body boarding. 

Her struggle with acne during her teens and 20s led to a holistic and healthy approach to skincare, embracing skin as an organ to be loved and cared for rather than a canvas to wage war on. 

Since 2008, she's been developing all-in-one products for a simple routine at home, & Rain Organica started when her backpacking friends asked for a portable skincare routine to keep their skin healthy & happy on and off the trails.

You can try Rain Organica for yourself with The Essentials Kit, a complete skincare routine in just 3 steps.

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