The Truth about Tamoxifen

The Truth about Tamoxifen

This patient-friendly article is about the drug, Tamoxifen, a long-standing hormone therapy, used to block and modify cellular receptor sites from the action of ooestradiol. It is used to treat breast cancer in women and men, and prevent breast cancer when risk is high. It is now being studied with other cancers but many women regard its use as controversial.


This article aims to objectively spell out the risks and the benefits - from the latest research.


Tamoxifen and breast cancer


Tamoxifen is sold under the brand names of Nolvadex, Soltamox and Tamofen amongst others. It was originally developed by chemist Dora Richardson in 1962, and the patent has expired and cheap generic versions, often from Third World Countries with little check on drug quality, are most commonly used. It is taken daily by mouth.


It is licensed to treat breast cancer in both women and men and to prevent cancer in women. Most usually it is used with premenopausal women. Most Doctors would not argue for its use as a prevention therapy, but it is used to reduce the risk of breast cancer recurrence. It's action is to bind to receptor sites on cells, modify them, and prevent human oestrogen (especially Oestradiol) binding to that site and causing havoc inside the cell. There is a little evidence that it can also prevent chemical oestrogen (xenoestrogen) from herbicides, pesticides and personal care and in-home products attaching to those sites.


The effectiveness of Tamoxifen and increased survival 


Surprisingly, the effectiveness of this widely accepted drug is actually pretty poor. Oncologists at the Royal Marsden in the UK typically tell women with breast cancer that they may be taking the drug for up to ten years and that it has a beneficial effect of between 1-9%, according to a large number of women who had been treated there. Mixed messages repeatedly occur and a 3-5% effectiveness in increasing survival seems the most likely benefit.  Either way, this is hardly the wonderful drug it is touted to be. Much ado about nothing really.


Interestingly, the third group of 'oestrogen', namely the much weaker phytoestrogens, can be very helpful. In a review (1) of available research, CANCERactive researchers showed that in all seven major research studies, genistein from Soy or Red clover actually increases survival times in women with ER+ve breast cancer and that soy makes tamoxifen work better. This research is contrary to the Medical Mythology often touted in Hospitals that women should avoid natural compounds like soy, flaxseed and resveratrol when fighting an ER+ve cancer.


Professor Trevor Powles, former head of the breast cancer unit at the Royal Marsden called phytoestrogens 'anti-oestrogens', because they possessed none of the chaos-causing properties of their human oestrogen cousins. Dr Young S. Kim, head of Nutrition and Cancer at the National Cancer Institute concludes that genestein is one of her 9 top natural compounds for preventing cancer recurrence.


Other compounds are known to modify receptor sites to block oestradiol, include, for example, indole 3 carbinol and melatonin.


The Dose of Tamoxifen


The dose is usually determined by the weight of the patient; although typically 20 mg is used for most women (2).


However, there has never been a variable-dose Clinical Trial, so no one knows if this is really the best dose for the drug.


In 2018 Italian researchers argued that different doses have never been studied for their relative effects and that their research actually showed that 5 mg would do just as well as 20mg (3).


Other studies (4) have shown that melatonin (up to 20 mg before bed) and 'total' vitamin E (with all 8 tocopherols and tocotrienols) each improves the action of Tamoxifen and women can achieve the same results as a normal dose with 25% less tamoxifen (i.e. 15 mg).


One often-quoted study suggested that turmeric shouldn't be taken with Tamoxifen because it reduced its effectiveness, but many other studies suggest the opposite is really true and turmeric prevents Tamoxifen breakdown (5) in the small intestine, and/or liver, and should always be used with Tamoxifen to increase effectiveness.


A number of studies suggest that EMFs reduce the effectiveness of the drug.


Side-effects of Tamoxifen 


A 2009 report from the Mayo Clinic talked of Tamoxifen having 'significant' side-effects. While common side-effects include irregular periods and even induced menopause, weight loss, hot flushes and dry mouth and dry eyes, serious side-effects may include increased risk of osteoporosis, increased risk of womb cancer, increased risk of stroke, increased risk of pulmonary embolisms and even vision problems.


Pregnant women are advised to avoid the drug.


                                                            * * * * * * * * * * * * 


Tamoxifen - updated original article

Women with breast cancer, and even some of those who just want to prevent breast cancer, will know of the Holy Trinity: Tamoxifen, Aromatase Inhibitors and Herceptin the drugs that can fight and even beat breast cancer. 

In this CANCERactive article we cover Tamoxifen (or Tamofen, Nolvadex, or Soltamox). We will cover the benefits of Tamoxifen. And we will cover the dangers, risks and side-effects of Tamoxifen too. 

TAMOXIFEN blocks aggressive estrogen from sitting on receptor sites and creating cellular chaos

Approved by

the Medical Board. 

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Oestrogen, or Estrogen in the USA, can be a major driver of breast cancer (and other cancers).  Tests will be conducted to find out whether you are positive for oestrogen, progesterone or are HER-2 positive. Some women will be triple negative, meaning that none of these three is involved.

Oestrogen is known to drive many breast cancers by causing changes inside healthy cells, by causing stem cells to stay in this rapidly dividing state, and by even causing damaging mutations and epigenetic blockages.

You will hear that ’Oestrogen is the female sex hormone’. Actually, it isn’t. Human oestrogen is a Family of Chemicals in COMPETITION with each other for available cellular receptor sites. Oestradiol is the form that causes chaos in cells.

The family is in three parts:

     * Human oestrogen;

     * Chemical oestrogen (xenostrogen);

     * Plant oestrogen (phytoestrogen)

Human estrogens include Oestradiol, the dangerous sister of weaker Oestrone. Until menopause, both are produced in the ovaries, After menopause oestradiol is produced - in men and women - by aromatase enzymes on the C-16 pathway, principally from the fat stores around the body. It is called Aromatisation. 

Chemical oestrogens can be absorbed from some herbicides some pesticides and some in-home toiletry, personal care, plastic or detergent products -  some can act like a dangerous oestrogen, once in your body. These are called Xenoestrogens. 

There is a third group in the oestrogen family - Plant oestrogens, or phytoestrogens.

Phytoestrogens are far, far weaker than human oestrogen’s and, like Tamoxifen, can bind to, and thus block, receptor sites from the action of human oestrogen’s.

Typically, you will find phytoestrogens in greens, pulses, resveratrol, flaxseed, red clover and mushrooms. Unfortunately, some mis-informed people, even in Hospitals - will tell you phytoestrogens put total oestrogen up. That is not the issue. Plant oestrogens can block receptor sites from nasty oestradiol.  And since they are far, far weaker, the effect on the cell is far, far weaker. 

However, you need to eat a lot, and eat them every day because they are not as strong in their binding ability and they wash through the body easily. This is why many women choose to juice greens.

You can find out far more about Oestrogen and cancer, and ways of naturally combating it in our article on Natural aromatase inhibitors.

Go to: Natural Aromatase Inhibitors

Japanese women have been shown to have a much lower incidence of recurrence of breast cancer than Western women because of their high blood levels of natural aromatase inhibiors - plant oestrogens (Int Radiation Oncol 2005; 62).

Tamoxifen and other Breast Cancer Drugs

 1. Tamoxifen is used to block the oestrogen receptor sites on cell membranes. Thus human oestrogens - oestradiol, oestrogen or, chemical oestrogen’s, xenoestrogens, find binding to these sites less easy. 

Unfortunately, tamoxifen is itself a carcinogen. It is known to cause an increased incidence of endometrial or uterine cancer, and is a potent carcinogen in rat liver, where it forms covalent DNA adducts. It was declared a carcinogen by the World Health Organisation in April 1996. However, it is known to reduce the incidence of breast cancer moving to the other breast, and ’officialdom’ concludes that the benefits outweigh the risks. 

You will be given Tamoxifen if you are still pre-menopausal. It may well bring on menopause.

 2. Aromatase inhibitors (AIs) aim to block the production of human oestrogen in your body in the first place. These include Anastrozole (Arimidex); Exemestane (Aromasin) and Letrozole (Femara).  Human oestrogen is principally made in the ovaries pre-menopause, but up to 60 per cent of it can be made in other tissues and the balance changes as you age. Thus AIs are most often used in women who have already reached menopause.

However, there are repeated studies showing the ’best practice’ of 5 years on Tamoxifen then 3 years on Letrozole (or similar) might be wrong. A meta-study covered in The Lancet in October 2015, suggested that AIs were much superior to Tamoxifen (AIs better than Tamoxifen: See Here) reducing mortality by 15 per cent, and secondary endometrial cancer risk. However, they were more likely to cause bone problems.

3. Herceptin: Much work has taken place with women who are neither oestrogen positive (ER+) or Progesterone positive (P+). One ’breakthrough’ was finding a group of women (about 20 per cent of women in total) who were HER-2 positive. About half of these respond positively to a monoclonal antibody called Herceptin.

This seems to work well for several years, but like all drugs, cancer manages to evolve and the drug works less well. A further development is Pertuzumab (Perjeta) which has been shown to extend the ’life’ of Herceptin. In some hospitals both Pertuzumab and Herceptin are prescribed simultaneously.

In 2015 the new drug Tyverb (or in the USA, Tykerb, or Lapatinib) was approved for use with Herceptin. Excited scientists were even claiming the total elimination of some cancers (Tyverb and breast cancer: See HERE). However, several women have reported to us that their UK oncologists have been having no such success with the drug.

Helping reduce your Oestrogen levels naturally

Readers should also look at the benefits of Indole 3 carbinol/DIM, (Go to: A review on Indole 3 carbinol), which can down regulate oestradiol to its safer sisters. The natural compound, derived from foods such as broccoli, also works against non-oestrogenic cancers along the p27 pathway. It can also modify the cell membrane receptor sites to make them less attractive to oestradiol. Some US hospitals are actually prescribing it for ER+ breast cancer patients.

Melatonin, a hormone available as an over the counter supplement outside the EU is also extremely beneficial. Melatonin, is produced by the pineal gland about 1 hour after you fall asleep. It puts you into a deeper sleep. It is now known to be produced by certain healthy gut bacteria. Melatonin is the most powerful antioxidant we produce as animals. It is also very anti-inflammatory, which is why sleep is so healing. Importantly it regulates plasma levels of oestrogen and growth hormone, both drivers of breast cancer 

(Go To: Melatonin - Self-defence against cancer). 

There is research in Cancer Watch that shows sleep (melatonin) helps Tamoxifen work better. Like I3C, melatonin has been shown to regulate the receptor sites stopping oestradiol’s actions; and they both have epigenetic benefits, being able to correct blockages stopping essential DNA message production.

Go To: Melatonin helps chemo work, increases survival, reduces side-effects

Red clover, a herb with the active phytoestrogen genestein, also helps block dangerous human oestrogens.

The City of Hope Hospital in Los Angeles have conducted research on natural aromatase inhibitors and have been giving women one and a half cups of white, button mushrooms which they say contain aromatase inhibiting factors. 

Go to: White button mushrooms help in breast and prostate cancer

Other research we have covered has signalled the importance of good levels of omega 3 and vitamin B-12. In a 2008 study from the University of Toronto, women with good blood levels of magnesium and vitamin D survive far longer than those with deficiencies. And women who take daily exercise double their survival rates.

Approximately, 93% of women with breast cancer were found on diagnosis to be deficient in vitamin D. Worse, other research shows that blood levels of vitamin D are indicative of survival times. Women with low levels survive least. Boston Medical School have been researching vitamin D for over 20 years and recommend people with cancer supplement with 5,000 IUs of vitamin D a day. That would equate to 4 hours on the beach in the sun. A study from Edinburgh University confirmed the importance of vitamin D supplementation.

Go To: Vitamin D supplementation increases breast cancer survival

If you are thinking of buying Vitamin D you might like to look at the Natural Selection Product of Choice.

                                                                                                                              You can do this by clicking here

The actions in breast cancer of Tamoxifen (or, Nolvadex D, Soltamox, Tamofen)

Tamoxifen has been the most commonly prescribed drug in the UK to treat breast cancer since its approval in the 1970s. It is given to both pre- and post-menopausal women. It is given after surgery to prevent breast cancer returning; it is given in advanced cases to reduce spread; and it is given as a preventative supplement to prevent breast cancer in high risk cases. It is still the pre-eminent drug for pre-menopausal oestrogen positive women with breast cancer. It is also given to men with breast cancer.

It is claimed that Tamoxifen has played a huge role in breast cancer treatment and has helped produce a 30 per cent reduction in mortality from breast cancer since 1990 despite an increase in incidence. It is normally prescribed for a period of a maximum of 5 years.

Tamoxifen is often described as the anti-oestrogen as the simple explanation for its action has always been that it blocks the oestrogen receptor site on the walls of cells, preventing oestradiol (a dangerous member of the oestrogen family) causing its havoc inside your cells. It is thus prescribed for women who are oestrogen positive (ER+). It will not work if your cancer is not oestrogen positive.

(Readers might also like to read Oestrogen the killer in our midst for tips on how to control oestrogen levels naturally - Go to: Buy Book: Oestrogen - the Killer in our midst)

In blocking oestrogen receptor sites, Tamoxifen helps slow the growth and reproduction of breast cancer cells. In 1998, Tamoxifen became the first drug to be approved by the American FDA to prevent breast cancer after research showed it halved the chances of the disease developing in women at high risk. This may now be seen as an exaggeration. Patients can be assessed individually by their oncologists. Some patients have a forecast survival increment of just 1.5%.

An internet trawl shows many claims for Tamoxifen, that nowadays just don't feel correct - e.g. Tamoxifen can ...

   1. Lower breast cancer risk in high-risk women by almost 50 per cent

   2. Shrink larger ER+ tumours prior to surgery

   3. Slow, or even stop, tumour growth and spread in advanced breast cancers

   4. Reduce the risk of a cancer returning in the same breast by 30-40 per cent in pre-menopausal women; and by 40 to 50 per cent in post-menopausal women who are ER+

   5. Reduce the risk of a cancer appearing in the other breast by 50 per cent

Oncologists at the Royal Marsden don't make any such claims!

The Possible side-effects of Tamoxifen

At the same time as blocking oestrogen’s action in breast cells, it appears to stimulate its action in liver and bone cells! On the positive side, there are claims that it can stop bone loss in older women, and even lower your cholesterol!

A number of doctors now prescribe bisphosphonate drugs to women who are clear of spread to the bones. Again, US research on the Internet claimed that bisphosphonates could strengthen the bones, and reduce the spread of breast cancer, whilst increasing survival.

A CANCERactive review of available research showed serious concerns over these claims, highlighting brittle bones from Breast cancer drugs made worse over 5 years by Bisphosphonates.

Tamoxifen is not without controversy. In icon magazine’s Cancer Watch (which publishes the latest research from all over the world) over the last 8 years we have covered, for example:

        1. That four-fifths of US women who have the side effects fully explained to them, subsequently do not want to take it as a preventative agent (Cancer, 2005)

        2. That researchers in the UK concluded it should not be used as a preventative agent, the risks outweighing the benefits

        3. That tamoxifen’s effects stay with you for 5 years after the end of usage (J Nat Can Inst 2007; 99, 272-282)

        4. That tamoxifen can increase the chances of endometrial cancer three-fold (Int Journal Gyn Cancer 2007)

        5. That tamoxifen usage for 5 or more years can cause a more dangerous ER-ve cancer in the other breast (Cancer Research online August 2009)

As if that was not enough, recent research studies have shown that the common view of how it works is not entirely correct. In fact,  many authoritative bodies didn’t really know how it worked anyway. For example, Cancer Research UK (December 2008) stated,  Previously, it was known that tamoxifen worked by blocking oestrogen from causing unchecked cell growth in breast tissue............. by switching certain genes on........ but the mechanism by which this occurred was unknown. Hardly reassuring to users, and difficult to understand how it was originally approved if we didn’t know how it worked. Herbalists have been called quacks for less.

A big concern has been tamoxifen resistance which can develop in some women users and no one seems to know why. The CRUK statement above prefaced a study by CRUK Cambridge Research Institute workers into the problem. They discovered (Nature, Dec 2008) for the first time the mechanism by which tamoxifen operates. It switches off a breast cancer gene ErbB2 via a protein Pax2, which keeps it off. Tamoxifen resistence occurs when the gene is on.

Other research studies covered in Cancer Watch have suggested that tamoxifen can itself cause genetic mutation.

On the knotty problem of tamoxifen resistance German Researchers seem to have shed some light too. Researchers from three German Universities have shown that Electromagnetic Fields (thought by many to be capable of causing breast cancer) can result in a lower sensitivity to tamoxifen. The researchers were convinced that EMFs reduce the efficacy of tamoxifen.

Also identified has been the need for an enzyme (CYP2D6) to convert the drug tamoxifen to its active form. In about 10 per cent of cases this conversion doesn’t happen. It can be worsened by certain drugs such as Prozac and other anti-depressants (SSRIs and SNRIs) and drugs like Benedryl. You must check out all other medications they might stop your tamoxifen working.

Side effects can include: hot flushes, irregular menstrual cycles, unusual vaginal discharge or bleeding, irritation of skin around vagina.

There can be increased risk of blood clots, cancer of the womb lining (endometriosis) and an increased risk of stroke or thrombi-embolism.

6 per cent of women on tamoxifen report impaired vision due to cornea and retina damage.

Astra Zeneca has reported it can cause liver damage and there is a 6-fold increase in the risk of liver cancer. So, technically, it is actually a carcinogen and in 1996 was declared one by the World Health Organisation. The National Health and Medical Research Council in Australia has reported that there is no safe dose to reduce risk of liver cancer.

Developments: US research showed that the use of natural vitamin E (especially tocotrienols) meant 25 per cent less tamoxifen needed to be prescribed. Similar research has shown that indole 3 carbinol supplementation means less drug is needed for the same positive effect.

Usage: Tamoxifen is taken orally in tablet form or in a sugar-free syrup. Most doctors recommended it is taken at the same time each day.


1. Soy increase breast cancer survival, aids tamoxifen effectiveness 

2. Tamoxifen, prescribing information

3. Is Low dose Tamoxifen the way forward 

4. With Melatonin you need less tamoxifen for same result

5. turmeric prevents tamoxifen breakdown

Other pages you might like to read 


Natural Alternatives to Aromatase Inhibitors


Red Clover

Omega 3


Go to:  10 ways to improve your chemotherapy success and reduce side-effects

Other articles that you may find interesting are:

  1. A diet for Chemotherapy
  2. Immunotherapy overview
  3. A to Z Guide to Complementary Therapies

Go to: Return to the CANCERactive drug list


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