Photo courtesy of and micromoth

Photo courtesy of and micromoth

Red Clover Controversy – Safe For Breast Cancer Or Not?

As a natural therapist I have always considered red clover to have some wonderful healing qualities and any studies I did on red clover appeared to confirm this. I never considered that it might have potential harmful effects until I was faced with breast cancer and began to hear lots of conflicting advice about it.

Red clover has long been considered an anti-cancer herb.  After all, it is one of the constituents of the Hoxsey formula, Jason Winters Tea and in some formulations of Essiac tea, although not the original formulation.

Red Clover’s Benefits

Red clover has been used for centuries for its blood cleansing and anti-cancer properties, it has also been used as a natural diuretic, nerve tonic, expectorant, demulcent, mild laxative, gentle antispasmodic, and it is a natural blood thinner (so should not be used by anyone on blood thinning medication).

The wide range of benefits discovered over the centuries for red clover is most likely due in part to the nutrients found within it which include vitamin C, magnesium, calcium, chromium, niacin, thiamin, phosphorus and potassium.  Probably the most important constituents, however, of red clover are the isoflavones, which are polyphenolic compounds capable of exerting estrogen-like effects.  And it’s that last bit that is causing all the controversy.

Phytoestrogens Are Misunderstood!

Phytoestrogens, literally “plant estrogens” mimic the hormone estrogen.  Many doctors will warn you against them if you have breast cancer, their reasoning being that phytoestrogens may increase the amount of estrogens in your body and if you have hormone-dependent cancer, is something you should avoid.

While I was doing the research for this article, I came across a lot of websites that warned against phytoestrogens for breast cancer.  The American Cancer Society stated on their website “Women who have had estrogen receptor-positive cancers or who are pregnant or breastfeeding should not use this herb.”   The National Center for Complementary and Alternative Medicine stated on their website: “It is unclear whether red clover is safe for women who are pregnant or breastfeeding, or who have breast cancer or other hormone-sensitive cancers.”  The webMD website stated: “Red clover might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, don’t use red clover.”  Okay, that’s the anti-phytoestrogen stance.

Here’s some research for you which indicates they could all be wrong.  The June 2004 edition of Breast Cancer Research states that “red clover does not cause any estrogenic increase in breast density, while human and synthetic estrogen does.  An increase in density is associated with a higher risk of breast cancer, inferring that taking red clover could prove to be preventative.”

The most interesting research I found was done in 2008.  This large study, Red Clover Isoflavones Are Safe And Well Tolerated In Women With A Family History of Breast Cancer was done at the Royal Marsden Hospital and the University Hospital of South Manchester, England.  The lead investigator for the study, Professor Trevor Powles, a well respected oncologist and breast cancer expert, said “Reassuringly for women, this study shows that these phytoestrogens do not cause any oestrogenic increase in breast density in women who have a family history of breast cancer. This would indicate that they are unlikely to cause an increased risk of breast cancer. This 3-year study confirms similar findings from previous, shorter-term studies.”

Let’s Clear Up This Controversy

Most herbalists agree: phytoestrogens are much weaker than the body’s own estrogens. They DO NOT promote cancer, in fact, quite the opposite.  Because of their extremely gentle nature they hardly exert any estrogenic effect on the body. 

How they work is to occupy estrogen receptors on cells, preventing stronger estrogens from the body, together with  xenoestrogens (environmental estrogens), from having any effect.

Through this mechanism they may help to prevent cancer growth and have a balancing effect on the hormonal system. This is why so many of the herbs used to treat cancer are rich in phytoestrogens.

Professor Trevor Powles has renamed phytoestrogens “anti-estrogens”, because of how they are capable of blocking the action of human estrogens in the cancer process.  He believes that phytoestrogens have the ability both to block the receptor sites to which human estrogens attach, and also in some cases to even denature aggressive human estrogens.

Red Clover Also Useful For Increasing Bone Density

In addition, I found some research which indicated that phytoestrogens increase bone density, which is a considerable concern to women who are on post-breast-cancer hormonal therapies as bone loss is one of the side effects of these drugs.  At the University of Bari in Italy, this interesting study indicated that phytoestrogens found in red clover can actually increase bone density, making it a helpful herb for the treatment of osteoporosis.

One last thing to note.  The University of Maryland advised against taking red clover at the same time as tamoxifen because it could interfere with its action.  Indeed — it may even act much in the same way as tamoxifen by blocking the estrogen receptor sites!  I know which one I would rather take.

I hope this article helps to clear the controversy surrounding red clover and phytoestrogens.

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