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Are Bioidentical Hormones Safe?

Hormone replacement therapy for menopause grew to prominence in the 1990s, when millions of women were sold hormones made from horse urine. Premarin (from the words “pregnant mare urine”) was promised to prevent age-related diseases. When the truth got out, in 2002, that the opposite was true—it actually increased risk of heart disease, stroke, pulmonary embolism, and invasive breast cancer—the number of prescriptions dropped, and so did the rates of breast cancer.

Thanks to some high-profile celebrity endorsements, interest then switched to so-called “compounded bioidentical hormones,” from plant rather than equine sources—which were said to work the same, without carrying the same risks. But, what does the science say?

In my 4-minute video, Plant-Based Bioidentical Hormones, I note there’ve been several new reviews on the subject from the American College of OB/GYNs, the Mayo Clinic, and the editors-in-chief of the Journal of the International Menopause Society. They all concluded that bioidentical hormones—being bio-identical!—carried the same risks, benefits, and side effects—which we now know is not a good thing. Even worse, when the FDA actually analyzed bioidentical hormone batches to see if the contents matched the label, nearly a third failed the analysis. Even in the same bottle, the dose of hormones could be all over the place.

How do we know all these medical authorities condemning bioidentical hormones aren’t just in the pockets of drug companies that don’t want the competition? After all, there are literally billions of dollars at stake. Whenever I’m skeptical, I turn to The Medical Letter on Drugs and Therapeutics, considered one of the least biased sources in medicine. It’s kind of like the Consumer Reports of the drug world—and, in fact, was actually co-founded by the co-founder of the publisher of Consumer Reports, more than 50 years ago. As The Medical Letter likes to brag on their website, they do not accept grants (from any source), donations (from anyone), or funding (from any entity). They won’t let their work be used for promotional purposes, and they don’t accept any advertising.

The Medical Letter on Drugs and Therapeutics recently reviewed bioidentical hormones, and came to the same conclusion: “There is no acceptable evidence that bio-identical hormones are safe or effective. Patients should be discouraged from taking them.”

Another way to rid oneself of excess estrogen is in the way nature intended. See my video: Relieving Yourself of Excess Estrogen.

We can also stop consuming steroid hormones. See my videos Anabolic Steroids in Meat and Acne & Cancer Connection.

For other ways to decrease breast cancer risk, see:

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death; More than an Apple a Day; From Table to Able; and Food as Medicine.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

21 responses to “Are Bioidentical Hormones Safe?

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  1. I’ve been on the Combipatch (“bioidentical” estradiol but synthetic progesterone) for about a year and a half. It’s a low dose and the when taken via skin (i.e., patch) it seems to be much safer. It’s been a miracle for me and several other friends who are going through or have gone through menopause. I am a vegan who eats a healthy whole food, balanced diet. I could not have survived this process of peri-menopause (which I am still going through) without the help of hormones. I’ve also had to cut soy out of my diet completely–soy oils, soy sauce, soy lecithin, everything–because it throws off the balance between the estrogen and progesterone and causes problems. Many women I know have told me that they have felt the HRT has been a “God-send” to them. I feel the same way.

  2. Someone is trying to use logic to say “there is no evidence” that bio identical hormones are safe. If no one has really studied it, how can same conclusion be drawn for synthetic hormones (such as Premarin and Provera) verses hormones that are bio-identical? Taking Bio-identical hormones helps with sleep, mood swings, depression, hot flashes, BUT if one decides not to take hormones, one could take an antidepressant and sleeping pills to help with symptoms of hot flashes, mood swings, depression and sleep. I’d rather take bio identical hormones, something identical to what my body made, than something synthetic and have quality of life. I am not careless about my health, I am vegan, gluten free, non GMO and eat lots of fruits and vegetables. I exercise regular, do not smoke or drink or use caffeine. Doing my best to live healthfully. I feel so much better taking bio identical hormones that I’m willing to go against the statement “avoid bio-identical hormones” and enjoy the quality of life that is worth it for me.

  3. I guess I just believe in letting nature do what it does. No additives here. I’m a vegan, and have been for 13 years. Hot flashes are mild, sleep is off (I have 3 dogs and a husband on the bed with me), moods are always changing (thank goodness or I wouldn’t know happy from sad). HRT is not for me, but then again neither is processed food or supplements of any kind. Why put anything that is processed/artificial into my body that I try to take good care of.

    1. Good for you but I agree with Lynn. I eat healthy, very healthy, exercise regularly and have been completely miserable with perimenopause since last December when I was 39, I’m not 40. My first doctor put me on Provera to start my cycle again and I hadn’t done enough research to know that it was a synthetic hormone at the time. No thank you. I’m most certainly not myself in the temper dept. or any other aspect of my life. I would rather try something that’s made from nature that makes me feel like me again by putting back in my body what’s missing. I have struggled with a hormone imbalance for almost 20 years and have no kids as part of that. If you can handle all the changes, kudos to you, not everybody can, me being one of them. I also don’t eat processed foods and hate taking any kind of meds to make me feel better.

  4. Is there new information or data on bio-identical hormone treatment? And my second question, are there any positive effects on Soy concentrate pills such as Selestra?

  5. I was tested by a integrative medicine clinic at age 52, and told I had the estrogen level of “an 85 yr old”. I was very worried about my bones. So I agreed to go on bio- identical HRT. I stopped it when I started bleeding again AFTER I had already been through menopause. Seven years later, I was diagnosed with Metastatic Malignant Melanoma!! I don’t know if the HRT was the cause of it, but it is suspicious to me. I had tumors in my heart, lungs and liver. Lucky for me, I was put on the new Immuno Therapy drugs, and 1 yr later I am in remission. Just think about what you are doing, and if you have any doubt / don’t do it. Just let nature take its course. Things could be worse…..

  6. Hi Dr. Gregor, it would mean so much if you could give me some advice because I really trust your input. I am 16 years old (turning 17 in 3 months) and i know I’ve hit puberty, but I still have never gotten my period. I’m pretty active (I do Irish dancing 5 or 6 days a week) and am 5’3 and about 107 lbs. I have been following a mostly plant based diet for around 6 months to a year now. I have a doctors appointment coming up and I’m really afraid that my doctor will want to give me shots of Progesterone, or make me stop exercising. Do you think it’s a problem that I haven’t gotten it, and is it better to just wait for it to come? Thank you so much for your time.

    1. Madeleine: I am by no means an expert. Please keep that in mind as you read my post.

      In one of the pages on this site (I wasn’t able to find it just now), Dr. Greger talks about how the average age for puberty in girls used to be 17 years. I think going through puberty as late as 17 is pretty rare now, but I understand that it’s rare because of the unhealthy diet and environment we live in. Though having more calories may also explain the changes in puberty timing. There is at least one page on this site that talks about early puberty as being a risk factor for cancer. So, going through puberty later seems like a good thing to me! If you are perfectly happy with your current situation, would it make sense for your doctor to push a serious drug on you? Or tell you to *stop* (yikes!!!!) exercise?!?

      Now, having said that, I have also read (I can get you a quote from a reliable source) that when women do not get enough calories, their periods often stop. I presume it also means that a body which is not getting enough calories would not start periods in the first place. You mentioned your weight, height and activity level. It doesn’t sound like you are starving to death, but I wonder (and again, this is from a complete lay person’s speculation) if you are not getting enough calories by just a smidge–by just enough to interfere with your cycle. Growing children and teenagers need more calorie dense (plant) foods than adults. (Here is a website Dr. Greger has spoken highly of and which has good information about diet and teens: and check this article: I wouldn’t want you to gain more fat than is healthy, but could you add some more healthy calorie-dense foods to your diet for a while to see if that makes a difference?

      I hope some of these ideas will help you. I also hope our medical moderators will jump in and give you some good advice.

  7. I have been taking natural progesterone cream because of a blood test that was specific for hormones. If I shouldn’t take this then what do you suggest that I take?

  8. Are there plants that one can eat to help boost progesterone or that mimic progesterone the way phytoestrogens mimic estrogen? Is there a way to help decrease very heavy menstrual bleeding, other than HRT? Specifically, heavy menstrual bleeding that is due to perimenopause?

    My doctor is prescribing a progesterone replacement, as I have had very heavy periods for the past 4-5 years and am trying to recover from iron deficiency. I do not have anemia, but my ferritin level is 6 and has been since at least August. Just with diet alone (no caffeine, lots of legumes, pumpkin seeds, mulberries, and potatoes combined with vitamin C-rich foods), I have brought my iron up from 40 in August to 70ug/dL in February, saturation up from 12% to 17%, TIBC from 325 to 420ug/dL, and transferrin up from 250 to 323mg/dL. But my ferritin has remained at 6ng/mL. I do exhibit symptoms of iron deficiency – shortness of breath, lack of energy, increased hair shedding. For this reason, I have started an iron supplement (iron bisglycinate).

    But the other component to remedying an iron deficiency is removing the cause. Hence, how to I slow down the bleeding? Any suggestions?

    Thanks in advance for any information you may have!

    1. Skip, I congratulate you for your proactive efforts using diet to bring up your iron levels. I searched both Medline Plus and PubMed for studies looking at nutrition to minimize menstrual bleeding, but other than a healthy diet, I could find no research. There was a very comprehensive article on heavy bleeding at Mayo Clinic outlining all the other approaches to treatment you may wish to review.
      While you did not say you have endometriosis, you might also want to check out this video because decrease in bleeding is mentioned with use of seaweed. Best of health while you attempt to have this challenge resolved.

      1. Thanks for the tips, Joan. Bladderwrack, as mentioned in the endometriosis video, sounds promising. I’ll give that a go.

        I’m also receiving ~weekly women’s balancing acupressure treatments. I’ll try to remember to post in a few months after seeing if there’s improvement in bleeding, just in case it’s helpful for another woman experiencing similar issues.

        Thank you for your kindness!

  9. To add to my last comment, I have just done some reading on the NIH’s website and found some articles that look at the use of botanicals, especially red clover, for the treatment of menopausal symptoms. Specifically, I found the article “Biological characterization of non-steroidal progestins from botanicals used for women’s health” interesting and encouraging. I would like to understand more the implications of studies like this; as a lay person, my understanding is limited and I don’t want to get my hopes up too much as this particular study involved testing on rats, and apparently not humans.

    Perhaps Dr. Greger would be interested in making a series of videos about phytoprogestins? It sure would be helpful for those wishing to avoid HRT.

  10. After being on birth control pills for more than 20 years, I went off a year ago after a surgery to remove fibroids. I am now experiencing extremely heavy periods that are a little irregular. After a lot of testing and ruling out more serious causes, we did repeated, timed blood tests and determined my progesterone is low. I have been plant based for 3 years (which has helped so many other issues) so I have a supportive diet already.

    If hormone replacement therapy of any kind is not recommend, how else can low progesterone be raised? This heavy bleeding is painful and causing low iron levels (among other issues).

  11. Hi Michelle Jacob, thanks for your question. The plant based food that encourages body to produce progesterone such as beans, cabbage, broccoli vegetables, grains and nuts. Foods such as walnut, cabbage and banana can balance the estrogen level. Prunes have iron and has good amount of fiber. Please consult your physician and Dietitian for further advice.

    1. Thanks for the information! I already eat an abundance of those progesterone boosting foods since I am already plant based, so I must need more than what food can provide unfortunately. Are there any other suggestions? Or have you found in your research other people like me who aren’t able to treat it with diet and must supplement with synthetic hormones?

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