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Which progesterone blockers are in your diet? Bloodroot, oregano, tumeric, and the skinny on phytoprogestins

When doing some research on phytoestrogens earlier last month, I came across information on molecules that perform the same antagonistic activity but this time with progesterone.  I hadn’t thought of this before, though it seems obvious to me now.  If some herbs and foods are going to interrupt with estrogen receptor activity, then some are going to interrupt with progesterone, too.   These effects are less dramatic and less well-known than those of estrogenic compounds, but worth investigating, still.

Dr. David Zaba is somewhat of an expert on the progesterone issue, and the bulk of the information I have dug up comes from his research.  This article is based primarily on his article estrogen and progestin bioactivity of foods, herbs, and spices.  That’s the pub med link, at which you can read an abstract.  I had a horrible time finding the whole thing, but finally did here! 

Zaba’s investigation found that there exist a wide variety of progesterone-inhibitors (as well as estrogen inhibitors, though I have discussed those at length already here and here).

Tables for the results can be seen here.

Using soy for a benchmark, with a value of 8 micrograms of estradiol equivalents per 200 g of substance, we can see how progesterone-binding compounds with values of 100 (that is, half as much as soy, so 4 micrograms of progesterone equivalents), 8, or 4 might be problematic for consumption in high quantities.   I would guess that only the ones that rank as high as 100 should even be considered blips on someone’s radar, especially someone with a fully healthy pituitary gland, but what follows is all of the information, just in case.  After all, a value of “8” listed below has around 1/12 the capacity of soy according to this research, which could be something someone would want to take into account.  That’s still higher than zero.

The herbs with the highest progesterone inhibiting activity are:

Table 3
Herbs and Spices Containing PR Binding Components

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Micrograms of Progesterone Equivalents/2 g Dry Herb
Bloodroot 100 Thyme 4
Ocotillo 8 Calamus rt. 3
Mandrake 8 Red clover 3
Oregano 8 Goldenseal 3
Damiana 6 Licorice 3
Pennyroyal 5 Mistletoe 3
Verbena 5 Cumin 2
Nutmeg 4 Fennel 2
Turmeric 4 Camomille 2
Yucca 4 Cloves 2
Herbs and spices were extracted and tested for their PR-binding capacity as described in the Methods. The 20 herbs and spices with the highest activity are listed and expressed in progesterone-binding equivalents. Values were rounded to the nearest microgram of progesterone-binding equivalents. Results are representative of at least two other assays.


It is supremely important to note, however, and in my opinion, that these effects may be compensated for by the pituitary gland and not constitute any noticeable changes in complete body chemistry.  They may play a role in extraordinarily sensitive bodies, but this research is by and large quite limited.


There is some other interesting information in this article.

Aside from demonstrating that progesterone- and estrogen- containing compounds exist in a variety of herbs, this research also shows that they actively inhibit hormonal activity via tests done on women’s saliva.   All estrogen-related herbs were negative antagonists.  Most, though not all of the progesterones, were as well.

Some of the herbs and spices found to contain high phytoestrogens and phytoprogestins were further tested for bioactivity based on their ability to regulate cell growth rate in ER (+) and ER (-) breast cancer cell lines and to induce or inhibit the synthesis of alkaline phosphatase, an end product of progesterone action, in PR (+) cells. In general, we found that ER-binding herbal extracts were agonists, much like estradiol, whereas PR-binding extracts, were either neutral or antagonists. The bioavailability of phytoestrogens and phytoprogestins in vivo were studied by quantitating the ER-binding and PR-binding capacity of saliva following consumption of soy milk, exogenous progesterone, medroxyprogesterone acetate, or wild mexican yam products containing diosgenin. Soy milk caused a dramatic increase in saliva ER-binding components without a concomitant rise in estradiol. Consumption of PR-binding herbs increased the progestin activity of saliva, but there were marked differences in bioactivity. In summary, we have demonstrated that many of the commonly consumed foods, herbs, and spices contain phytoestrogens and phytoprogestins that act as agonists and antagonists in vivo.

This shows, again, that the antagonistic effects of phytoestrogens and phytoprogesterones are real if complicated, and the true effects of them in the context of the whole body unknown.  It’s worth re-stating the bold section of the abstract: “Soy milk [an example of a phytoestrogen] caused a dramatic increase in saliva ER binding components without a concomitant rise in estradiol. Consumption of PR-binding herbs increased the progestin activity of saliva, but there were marked differences in bioactivity.”  Soy displaces true estrogen, which blocks estrogen activity, and signals to the body to down-regulate production of estrogen.  This was my hypothesis in this article, as well.

The relative “different activity” seen in progesterone-binding activity is as follows.  The results are largely elevated over controls — neutral conditions — though some compounds inhibit activity in the saliva more strongly than others.

Figure 3 – nmoles PNP formed/min / µg protein
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Figure 4 – fmoles Estrogen Receptor/ µg DNA
Back to the Table Of Contents
Figure3 graphic - Induction of alkaline phosphatase by progesterone plus RU486 and PR binding herbal extracts Figure 3 Induction of alkaline phosphatase by progesterone plus RU486, and PR binding herbal extracts, with and without progesterone. Near confluent cells in 96-well plates were exposed to increasing doses of progesterone, 10-9M progesterone plus 10-7MRU486 or 1/500 dilution of herbal extracts (as indicated) without or with 10-9M progesterone. After 48 hr, cells were fixed and alkaline phosphatase measured directly in the plate as indicated in Methods Figure4 Graphic - Down regulation of ER by progesterone and herbal extracts in the absence and presence of RU486Figure4 Down regulation of ER by progesterone and herbal extracts in the absence and presence of RU486. Near confluent cells in 24-well plates were exposed to progesterone and herbal extracts, without or with 10-9M RU486. After 48 hr. ER wa measured directly in the plate by incubating cells with 2nM [125l]-estradiol. Following incubation, the cells were removed from the plate with trypsin and the radioactive binding of [125l]-estradiol was meansured in nuclei as decribed previously. (11)


All of which is to say, as in the case with phytoestrogens, that these are not serious health threats in the slightest.  Unless you consume grams worth of these herbs every day you should not witness a difference–and perhaps not even then, depending on your personal physiology and response to these herbs.  This information is, again, just a note for those of us doing some serious personal experimentation and investigation, or otherwise interested.  It all just goes to show how imtimately we are what we eat.  On the other hand, this kind of data and the overwhelming complexity of it all may be an indication that we should throw nitpicky nutritionism out the window and just instead focus on eating real foods in decent balance.

Whichever suits you, your body, and your soul at this point in time.



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Managing director of Paleo for Women and author of Sexy by Nature.


  1. hi there, can you help me it out? I do not know alot about this stuff so im jsut trying to figure out if these herbs are harmful to our health or are they helpful in getting rid of estrogen and progeaterone in the body?
    thanks so much

    • I personally try to steer away from hormonal influences, if that helps.

  2. What happened to your post about Matt Stone? I clicked over from Google Reader to read the comments and the post is gone.

    • I thought better of it. I usually refrain from spur-of-the-moment advocacy without deep thought. I’ve been thinking about his argument and whether or not I think it has scientific merit for weeks now. It’s possible I’ll post on it soon.

  3. So are you saying tumeric doesn’t boost progesterone, but rather inhibits it?? I purchased it because they say it boosts progesterone, but not true???

    • This is the first time I have ever heard turmeric inhibits progesterone. All due respect to the author, but she is incorrect on this one. Turmeric has been used for centuries to help increase progesterone (they obviouslyhad different terms back then but that is what it boils down to). My family has been using thisto help with menstrual difficulties for generations.

  4. While some people may dismiss herbal remedies as quackery, the use of botanicals is well rooted in medical practice. Ancient doctors methodically collected information about herbs and developed well-defined pharmacopoeias to treat a variety of ailments. More than a quarter of all drugs used today contain active ingredients derived from those same ancient plants….:”

    Have a look at all of the helpful posting on our new blog site http://healthmedicinebook.comup

  5. How is it now, does oregano inhibit or boost progesterone? I’ve seen some sites where it’s said to be a booster…

  6. Is oregano a progesterone booster or inhibitor? I’ve seen some sites..

  7. I’m a master herbalist and have been in the HRT business for 17 years, I formulated and manufacture HRT creams and own a diagnostic laboratory where we test hormones in saliva. I am an expert in HRT and herbs and can tell you that what this web site is saying is completely correct!

    I’ve been researching the effects of the many chemical compounds in herbs for a long time, and educating women about food and drinks that will block hormone receptors. In the scientific community these chemicals are called ‘hormone disruptors’.

    This is the only web site I have ever seen that is aware of this too, and is alerting women.

    David Zava’s list is very small though. I have a much larger list.

  8. Okay, after reading all the posts I have more to say. First of all, not only do the chemicals in many herbs fit into hormone receptors in the body, they also fit into the antibodies in a hormone test. When David Zava tested all these herbs it ‘appears’ that they are making the body produce hormone when, in fact, they are just reading like the hormone.
    Turmeric does not tell the body to produce progesterone (I‘m referring to Catie’s post). Just because someone is told that an herb is doing something, doesn’t mean that it’s true. I have over 30 herb books and they do not all agree about what each herb does. The only way to really know what a substance does is to read the scientific studies that have been done on it.
    Progesterone stops too much estrogen from getting into the cells the last 2 weeks of the cycle, so when it’s not there, too much estrogen enters the cells and the woman bleeds heavily. This is a condition known as ‘estrogen dominance’ and is caused by the lack of ovulation. The effect that Turmeric has on the menstrual cycle is to fit into ‘estrogen’ receptors and block the body’s own estrogen from getting into the cells. It does not cause the body to make progesterone, but it creates the same end result as progesterone, herbalist who don’t understand what’s going on ‘think’ that it’s causing the body to make more P.

    • Sindi, I’d like to see your larger list. I found this site while researching herbal effects on hormones because I started getting migraines after I had my only child. I saw an Ayurvedic nutritionist who prescribed me a long list of herbs. During the 7 years of treatment other ailments I had improved, but the migraines got worse and more frequent, until I had one almost all the time. I became nonfunctional, bedridden, throwing up about 50 percent of the time. I saw another nutritionist, and she did not tell me to stop the herbs, either. I was prescribed a progesterone cream that helped somewhat, but not completely. Finally a psychic told me to stop taking the herbs, that they were causing the migraines. I did, and the migraines went away. Of course the nutritionists have nothing to say for themselves, like I am just a complete anomaly. I am still using progesterone cream, but less, and taking a lot of vitamins/minerals. My theory is that the herbs were blocking progesterone, and turmeric is one of those, I believe, that really harmed me, because a recommended curcumin-based “herbal painkiller” made the headaches worse with more nausea. Anyway, a lot of conflicting info out there, so about that list…

  9. Again, only website out there that says turmeric inhibits progesterone. I have been drinking tons of it because every it he site out there says it helps to raise it. I’m 6 weeks pregnant and my progesterone went from 13.. already low.. to 8.. too low 🙁

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