Phytoestrogens Are Not Estrogen

Phytoestrogens are a special group of phytonutrients that occur naturally in almost all plant foods. The two major classes are isoflavones in soy, and lignans in seeds, whole grains, legumes, fruits, and vegetables.

They’re called phytoestrogens because they interact with estrogen receptors but they’re not estrogen. In fact, they bind so weakly to estrogen receptors that they effectively block estradiol and are therefore better classified as ANTI-estrogen.

It’s long been observed that isoflavone crops such as red clover suppress the estrogen and fertility of livestock and it’s even been proposed that plants evolved phytoestrogens to reduce the fertility of female herbivores and prevent overgrazing.

In a chapter called “Agriculture and Selection for High Levels of Estrogen,” evolutionary biologist Grazyna Jasienska makes the case that ancient humans adapted to agriculture and phytoestrogen-rich plant food by upregulating endogenous levels of estrogen. Those of us with agrarian ancestors are, therefore, probably “hormonally calibrated” to a relatively high intake of food-based phytoestrogens to shelter us from our own high estrogen.

So, what does this mean for period health? Well, for one thing, it’s fine to eat phytoestrogens like legumes and seeds. They’ve long been part of our traditional diet, and our hormonal system is adapted to them.

How phytoestrogens affect women’s hormones

During the reproductive years, when estrogen is high, phytoestrogens have a beneficial anti-estrogen effect and can help to promote the healthy metabolism or detoxification of estrogen. Food-based phytoestrogens may even help to prevent hormone-sensitive cancers.

Heavy periods. By reducing estrogen, phytoestrogens generally make periods lighter. However, if the dose is high enough to suppress ovulation and progesterone (the hormone that lightens periods), the result can be a heavier period.

Endometriosis. In general, phytoestrogens should be neutral for endometriosis, or even slightly beneficial. Some women with endometriosis report a worsening of symptoms with soy which is probably due to an immune reaction. Read Endometriosis? Treat the Immune System.

PCOS. Phytoestrogens can improve insulin resistance and have been found to have a beneficial effect on the hormonal condition polycystic ovary syndrome.

Hypothalamic amenorrhea. Phytoestrogens cannot correct the estrogen deficiency of hypothalamic amenorrhea. The treatment for hypothalamic amenorrhea is to promote ovulation by eating more. Read my blog post about estrogen deficiency.

Menopause. During menopause, when estrogen is low, phytoestrogens can have a mild pro-estrogen effect. That has led to a great deal of research into the use of phytoestrogen supplements such as soy as an alternative to menopausal hormone therapy. From hundreds of studies and a few meta-analyses, it appears that isoflavones may help hot flushes, but don’t do much, if anything, for other symptoms of menopause.

Thyroid disease. Concentrated extracts of soy isoflavones may suppress thyroid function. Food-based soy is probably okay as long as you also have enough iodine.

In conclusion, phytoestrogens generally have a beneficial anti-estrogen effect in women. They have a mild pro-estrogen effect in menopausal women, which may be beneficial, and a pro-estrogen effect in men and children, which may be detrimental at a high dose.

Ask me in the comments.

31 thoughts on “Phytoestrogens Are Not Estrogen”

  1. Hi Lara,

    I don’t get my period or ovulation and I have little facial hair on my chin. I have been taking zinc, magnesium, vitamin D and myo inositol because the doctor said I have PCOS. And I just started taking P-plus cream which is a natural progesterone but I spot each time I apply it to my skin and also expressing breast tenderness. Should I continue with all the supplement and also get iodine like you recommended in your book, will it help me ovulate/ conceive.

  2. Hi, thank God I found out about you yesterday and decided to read your book period repaid manual. I was diagnosed with PCOS when I started trying to have baby and now Mild left hydrosalpinx with overflow spillage on my Fallopian tube. I am about to start fertility treatment but after I came across your book yesterday. I want to do all natural treatment. I am currently taking Vitex, living bitters, vitamin D and fish oil. I need advice on how to go about it. Thanks

  3. Can flax or other phytoestrogens suppress or delay menstruation? I get flu like PMS and this month took flax during it on the assumption the flu like body aches were from estrogen withdrawal. The aches went away but the period never came. But I got egg white like discharge like I normally do around ovulation.

  4. Thank you very much. Yes, I`ve read that blog post and both editions of your books. Very helpful. With the information you are providing there I`ve eliminated PMS and period pain. I am very grateful to you!

  5. Hi Dr Briden, awesome article! I’m a huge fan of your book! Question: where has this myth of phyoestrogens of causing higher estrogen levels come from??

  6. Thank you for replying. I love your book. There’s nothing like it. And I’ve bought it for so many people. You rule! Is the only cure for adenomyosis a hysterectomy?

  7. I did a month long siliva test for hormones. Both estrogen an progesterone were flatlined, with estrogen being slightly higher. That was 2 years ago, when I was 42. I have have severe symptoms (no cycle hot flashes, no sleep, terrible mood (crying and anger, when neither is normal). No one has been able to help. I would welcome any advice!

  8. Hi Lara-
    Is 45 too young to be through menopause? I’ve get hot flashes and night sweats but drinking soy milk and taking black cohosh has eliminated them. I suffered for many years from pmdd. Now that I no longer ovulate, I am completely symptomless. I’m just concerned that 45 is too young to no longer ovulate. Should I be concerned or just happy that I not longer suffer from extreme pms?

    • 45 is technically in the normal range for menopause but a little on the young side in terms of maybe needing a little support for your long-term bone health.
      Probably best to check in with your doctor, but yes, you might be in the situation where you can just be happy.

  9. No endo and never had birth control. Have had a normal pregnancy and birth as well. But i was terrified the whole time that I would accidentally eat soy and have a miscarriage!

  10. Hi Lara. Thank you for this. I have been thinking about exactly this subject! I have fibrocystic breasts, andenomyosis, extremely heavy frequent painful periods and I’m high risk breast cancer due to family history. I’m coeliac and don’t have gluten obviously, but I also avoid dairy as it makes everything much more painful. I recently tried using soya products instead of almond as they taste more neutral and after a few months I was in agony; I had a burst ovarian cyst and a huge painful cyst in my breasts. I’m off the soya now and it’s all calmed down. In light of your article – why would this be? The old ‘soya is good/soya is bad’ dilemma is a real pain for me and for my mother recovering from breast cancer. Kind regards, Liz.

    • I probably should have stated this in the article, but in general, I’m not a fan of soy. Not because it’s a phytoestrogen, but because it’s a common food sensitivity and can worsen inflammatory conditions like adenomyosis. There’s really no reason to have large amounts of soy but it should be fine to have a moderate amount of other food-based phytoestrogens.

  11. Thank you very much for very informative article. Would you recommend seed cycling in perimenopause. I am 46, still ovulating, have endo and thyroid nodules. Thank you!

  12. Hi Dr. Briden, I saw you speak a couple of years ago at Loom in Los Angeles. I was misdiagnosed with endometriosis (I had the surgery, no endo) due to symptoms of painful sex, painful periods, and hormone imbalances. I also had several hip surgeries. You suggested it sounded like my problems might be structural, rather than hormonal, and you were correct. I was abused by a pediatrician with medical instruments as a child and was recently diagnosed with vaginal nerve damage, vulvodynia, and vaginismus.

    Here’s my question to you: Back in the day, when I was still trying to get an accurate diagnosis, and doctors were focusing on hormones rather than structural diagnoses, my endocrinologist did a hormone panel and said my testosterone was on the higher end and put me on Spironolactone for acne. I was on it for about 3 years. I tapered off of it about 2.5 years ago because I didn’t see any progress with acne or other symptoms. I’ve never been on hormonal birth control.

    Today, I vaginally insert a verabase cream twice daily made with gabapentin, lidocaine, and estradiol. My gynecologist recently rewrote the prescription to include testosterone, which makes me very nervous because I thought my testosterone levels were already too high. I asked her why she added testosterone and she said that a lot of my vaginal pain during sex is because of the thin tissue, due to nerve damage. It’s not absorbing hormones, so it’s not as plump as it should be, which is why it feels like it’s burning. She said the estradiol and testosterone will help the tissue with plumpness. However, she said if I was uncomfortable with the testosterone, she can re-write the prescription without it.

    I’m already nervous and uncomfortable with the estradiol, I don’t want synthetic hormones interfering in my body. But she’s very, very pushy about wanting me to go on birth control. We’ve already had an argument about it. I have an appointment this Friday to discuss the prescription. Can you offer your thoughts on whether conditions similar to mine benefit from testosterone in the verabase cream prescription, and if there is any benefit to structural conditions like this from going on hormonal birth control?

    Thank you so much!

  13. Hi Lara, I’ve had the same issues as well with soy so I tend to avoid flax and any other food high in phytoestrogen because I had the worst hormonal acne. I was leaning on non dairy alternatives because i had my gallbladder out in my 20s. Dairy was just too heavy on my stomach. I continue to avoid milk to this day. Side thought, I look back now and realize that birth control probably caused my gallbladder issue. Now that I am off of birth control just recently, I’m almost 35, do I need to be concerned with a reaction to soy? Why does birth control cause a reaction to soy?

  14. What is going on with my wacky reaction to photoestrogens then? Ever since I was 20 or so I react to soy, flax, chia with breast pain, period type bleeding, and cramps. Thanks!

    • I’ve heard this kind of reaction from a few other commenters but I’ve never seen it with patients.
      Are you on any kind of hormonal birth control? or, do you have endometriosis? Because definitely, soy seems to be a problem for some women with endo, which I think is more of an immune reaction.

  15. Our daughter has recently discovered breast lumps which are looking like fibro adenomas on ultrasound. One is quite large. She is refusing to have a biopsy. Any help with healing and dissolving these would really be appreciated. I must get your book out and have another read!

  16. Hi Lara, do you have any thoughts on anti-inflammatory autoimmune protocol type diets? That is, diets that avoid not only wheat and dairy but also things like legumes and nightshades? Is a diet that extreme helpful or necessary? I was recently diagnosed with Sjögren’s Syndrome (which also affects sex hormones) and I am trying to figure out the best way to optimize my health, but it’s very overwhelming.

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