Artwork by xymonau/

Since many of my thrivers have expressed an interest in learning more about the role of progesterone, this article will share all about using progesterone for breast cancer, and why you may want to consider it.

Many studies have established that an insufficiency in the hormone progesterone can increase breast cancer risk. Because there is an interplay between the hormones estrogen and progesterone, low progesterone levels can lead to a condition known as estrogen dominance, which simply means too much estrogen in relation to progesterone. This can also increase breast cancer risk.

Natural Progesterone Slows Breast Cancer

If one has been diagnosed with hormone-driven breast cancer, knowing how the two hormones work can be life-changing. Yet it is usually not even discussed by our oncologists.

In 2015, scientists from the United Kingdom, Australia and the USA published a joint study that had some interesting findings. They determined that unlike synthetic progesterone, which can increase the risk of breast and other cancers, natural progesterone has the ability to slow or shrink the growth of breast cancer tumors. [1] Since then, another study had similar findings [2].

You’ll notice a lot of discussion about estrogen and progesterone receptors in that study, so allow me to explain what they are, and how they work.

About Estrogen and Progesterone Receptors

For years, researchers in breast cancer have understood that most breast tumors (about 2/3 of those diagnosed) exhibit both estrogen receptors and progesterone receptors on their surfaces. When it occurs, this is known as ER positive (ER+) and PR positive (PR+) breast cancer, and these types of cells have been deemed to have better treatment results than tumors that do not have these receptors.

This is how they work. Estrogen and progesterone receptors are found in many of the cells of our bodies, including the breast. They are the mechanism by which hormones (chemical messengers) are allowed to change the behavior of cells. Once hormones have docked with the cells via the receptor sites, they can change how particular tissues and organs function.

What occurs is that when an estrogen or progesterone molecule comes into contact with its respective receptor, the molecule docks with the receptor and activates it. When this happens, the receptor enters the nucleus of a cell and attaches to specific places on chromosomes that contain all of that cell’s genetic coding, in effect turning on or off specific genes that govern the behavior of that cell. This effect happens constantly – if the body has enough estrogen and progesterone to activate the receptors.

While researchers know how estrogen receptors act on cancer cells, they have spent a lot less time learning about what progesterone receptors do in those same cells, so the researchers in that 2015 study mentioned above [1] set out to rectify that lack of understanding.

In test tube studies, the researchers took breast cancer cells that were ER+/PR+ and exposed them to enough estrogen and progesterone to activate both types of receptors. They then examined what the receptors did within the cancer cells. Surprisingly, when activated the progesterone receptors attached to estrogen receptors. This reprogrammed the estrogen receptors to cease turning on genes that promote cancer cell growth. Instead, the receptors turned on genes that promoted apoptosis (cancer cell death) and promoted growth of normal, healthy cells. How cool is that? But wait – there’s more.

To see what would happen in vivo (in the body) the researchers ran tests on breast cancer tumors in live mice that had been implanted with ER+/PR+ breast tumors. Some mice were exposed to estrogen only, while others were exposed to both estrogen and progesterone. A third group received no hormones at all. After 25 days, researchers found that the mice receiving estrogen only exhibited tumor growth, while the size of the tumors in the mice that received both estrogen and progesterone decreased. Also, the researchers gave Tamoxifen (a pharmaceutical drug that inhibits estrogen) to some of the mice that had also been treated with progesterone. They compared the tumors of these mice to the tumors of the mice that received progesterone but not Tamoxifen, and while tumor growth was reduced in both groups of mice, the mice treated with both progesterone and Tamoxifen experienced the greatest tumor growth reduction. The cancer cells were about 50 percent smaller when given a mix of progesterone and Tamoxifen than those given Tamoxifen alone. That’s pretty significant.

The only problem with using Tamoxifen is its long list of potentially serious side effects.

So what form of progesterone was used in the research? (I can hear you asking) Natural, bioidentical progesterone – not synthetic progestins, which are molecularly altered in a laboratory and have been linked with increased risk of breast and other cancers.

Dr John R Lee’s Research

This isn’t really news for those who have read the 2002 book “What Your Doctor May Not Tell You About Breast Cancer” by Dr John R Lee, M.D., a pioneer and expert in the study and use of natural progesterone to treat hormonal imbalances. Co written with Dr David Zava, a biochemist and breast cancer researcher, the pair found that:

  1. Women with low progesterone levels and estrogen dominance are more likely to get breast cancer and have poorer treatment outcomes.
  2. When progesterone levels are brought up to normal, healthy levels, this turns on genes that are able to prevent breast cancer, as well as reducing the size of existing tumors.

Dr Lee had 3 rules for bioidentical hormone therapy [3]:

  1. Only take natural bioidentical hormones if you are truly deficient (don’t just guess at this, get yourself tested);
  2. Use bioidentical hormones rather than synthetic hormones;
  3. Only use enough bioidentical hormones to bring your levels up to normal – more is not better.

Dr Lee has been quoted many times as saying that women with hormone receptor positive breast cancers could especially benefit from natural progesterone supplementation. Yet his findings have long been ignored by the medical community, until this 2015 research [1] came along. To this day, many oncologists refuse to let their breast cancer patients use natural, bioidentical progesterone because they just don’t understand how it works.

Why Do Hormones Get Out of Balance in the First Place?

Hormonal imbalances among the general population have reached what some consider to be epidemic proportions. The main factors for this are poor diet, rising obesity levels, stress, lack of exercise, xenoestrogens in the environment (mainly caused by hormone-altering chemicals), all of which are causing many women to suffer from estrogen dominance.

If you suspect you have a hormonal imbalance, or if you have been diagnosed with breast cancer, here’s what I suggest:

  1. Get your hormone levels tested. In particular work with a doctor or naturopath who is trained in the use of natural, bioidentical hormones (meaning, it’s probably not a good idea to have your local general practitioner do this test as they will probably do a blood test, the results of which will be misleading). Generally, the more accurate testing is done via a saliva test, and five hormone levels are checked: estradiol (the stronger form of estrogen, and the one most linked to breast cancer), progesterone, testosterone, cortisol, and DHEA-S.
  2. If your levels are found to be low, you may need to take bioidentical progesterone and sometimes bioidentical estrogen to restore proper balance. It’s worth mentioning that when it comes to taking natural hormone supplements, the goal is to return hormone levels to “normal” – or what would be considered normal for a healthy person. In most cases, you only need relatively small amounts of bioidentical hormones. It is crucial to regularly re-evaluate your hormone levels while taking bioidentical hormones.
  3. It’s also important to eliminate from your life any hormone-altering chemicals with which you might be coming into contact. We are bombarded daily with toxic chemicals that were not in existence just a few decades ago. There are synthetic hormones in our water supply, in the foods we eat, and toxic pesticides in our air and water – many of which exert estrogen-like actions. See my articles Protect Yourself from Xenoestrogens & Estrogen Dominance and Unraveling the Mystery of Xenoestrogens and Estrogen Dominance for more information.
  4. Support hormone balance through nutrition and exercise. Our modern diets are full of too many of the foods that promote obesity and estrogen dominance, and our sedentary lifestyles make that worse. Simply by becoming more active and reducing your sugar intake, avoiding refined carbohydrates and foods high in trans-fatty acids, you can do a lot of good. Increase your intake of organic, cruciferous vegetables like broccoli, cauliflower, brussel sprouts and other vegetables, fruits, and fiber (fiber is especially beneficial as it helps to whisk excess estrogen out of the body).

What About Wild Yam Products?

There are many products available that claim to serve as natural alternative sources of progesterone. These products are made from soybeans or an inedible wild yam from Mexico called Dioscorea villosa. The wild yam products are available as a topical or vaginal cream or in capsules and for years have been promoted as being a natural form of progesterone. They actually do not contain any progesterone, but a phytochemical known as diosgenin.

Does diosgenin convert into progesterone? Dr John Lee had this to say: “Some companies are trying to sell diosgenin, which they label “wild yam extract” as a medicine or supplement, claiming that the body will then convert it into hormones as needed. While we know this can be done in the laboratory, there is no evidence that this conversion takes place in the human body.”

Now, I’ve taken wild yam cream myself on many occasions to help with menopausal symptoms like hot flashes, etc with minimal results. Most other sources I consulted while researching for this article concluded that applying wild yam extract topically or taking it internally will not result in increased progesterone levels in the body because the body cannot convert diosgenin into progesterone. A 2001 clinical study [4] found that menopausal women taking wild yam extracts had about the same outcome as those on placebo. After three months of treatment, there were no changes in progesterone levels.

So What To Do If You’re Too Nervous to Use Bioidentical Hormones?

For those who are told to not take bioidentical hormones by their doctors and are too nervous to go against doctor’s orders, you can try to raise your progesterone levels naturally. Here are the nutrients and lifestyle alterations that may assist with that:

Eat lots of healthy fats and cholesterol-containing foods. Progesterone is produced from cholesterol, so eating organic foods that will help to gently raise cholesterol levels will help progesterone levels in turn. Eat organic eggs, organic butter, organically raised meats, organic chicken, sardines, and wild caught salmon.

Eat foods that help stimulate progesterone production. These foods don’t contain progesterone, but they may help boost the production of progesterone. Include crucifers like broccoli, brussels sprouts, cabbage, cauliflower, kale. Also include beans, nuts, pumpkin, spinach and whole grains, and include loads of fresh berries and fruits that contain a lot of vitamin C.

Reduce cortisol levels. Cortisol is made out of the same precursor as progesterone, so when you have too much stress, you have elevated cortisol levels and reduced progesterone levels. Meditation and massage therapy can help with this. Also try to get more and better sleep – while this may not specifically increase your progesterone levels, it can help your body to heal, calm down your nervous system, reduce cortisol, and all of that is good for you. If you don’t sleep well, see my article Want to Sleep Better?

Use Castor Oil Packs. This may seem weird, but here’s why it works. To offset estrogen dominance, the body’s cleansing processes must be working well. Castor oil improves levels of glutathione, the body’s powerhouse detoxifier. Glutathione works to eliminate excess estrogens, toxins, and even xenoestrogens. A castor oil pack placed directly over the liver can exert a powerful effect that supports liver function and glutathione activity. Castor oil packs also reduce inflammation and relieve constipation, thus helping you to excrete excess estrogen. For more information on how to make a castor oil pack, just Google it, there are a number of good YouTube videos that will show you how. And always use organic castor oil, please.


[1] Progesterone receptor modulates ERa action in breast cancer –

[2] Progesterone vs. Synthetic Progestins and the Risk of Breast Cancer: A Systematic Review and Meta-Analysis –


[4] Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women –

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