Should Phytoestrogens be Avoided with Breast Cancer?
Clinical Herbalist Reviewed on June 25, 2013 by Paulina Nelega, RH
There is much conflicting and confusing information regarding the use of phytoestrogen-containing herbs, foods, or dietary supplements, especially when there is a history of estrogen-receptor-positive breast cancer (or a risk of it, e.g., family history). Some health care professionals advise to avoid phytoestrogens in these cases, while others recommend them as being protective. It is advisable to discuss the potential benefits vs. risks of phytoestrogens with your health care professional if you have (had) breast cancer or a history of it, before using phytoestrogen-containing foods, herbs, or dietary supplements (including Hair Essentials).
What are phytoestrogens?
Phytoestrogens are plant-derived molecules which can bind to our body’s estrogen receptors. They share a structural similarity with our own endogenous estrogen (in particular, estradiol). Compared to the tight fit that estrogen makes with the receptors, phytoestrogens bind only loosely. As a result, their estrogenic effects are much weaker: isoflavones, for example, are 400 times weaker than estrogen made in the body. Phytoestrogens may also modulate the concentration of our body’s estrogen levels by binding or inactivating certain enzymes, and/or altering the bioavailability of estrogen (and other sex hormones) by depressing or stimulating synthesis of sex hormone-binding globulin (SHBG), the protein that transports these hormones.
Phytoestrogens are widely distributed in many herbs and plant-based foods. They fall into three major categories, based upon their physical and chemical structure:
• Isoflavones (the most potent type of phytoestrogen) – found in many legumes including soy (Glycine max) and Red Clover (Trifolium pratense)
• Coumestans – found in various sprouting plants
• Lignans – found in flax seeds, many types of nuts, lentils, beans, whole grains, many fruits and vegetables
Phytoestrogens can either promote a mild estrogenic effect and/or an antiestrogenic effect in the body. This dual-action nature is termed amphoteric: when estrogen is low (e.g., menopause), phytoestrogens may provide benefit by increasing the number of estrogen receptors being bound (activated) and thus increase overall estrogenic effect. Conversely, when estrogen is too high or if there is an estrogen receptor-positive condition, phytoestrogens may help to block our own endogenous estrogen from binding, which is far more powerful. In the case of cell division/cell growth that is stimulated by estrogen, this feature may provide therapeutic benefit.
In 2011, data from the Women’s Healthy Eating and Living (WHEL) study were used to examine the effect of soy intake on breast cancer prognosis in 3088 breast cancer patients who were followed for 7.3 years. As soy isoflavone intake increased, the risk of breast cancer-related death decreased. This was the third epidemiological study to report no adverse effects of soy on the prognosis of breast cancer. It does not counteract the effects of tamoxifen and, in fact, may provide potential benefits in decreasing risk of recurrence or death from cancer.
If there is a history or risk of estrogen receptor-positive breast cancer, or if one is on any treatment for breast cancer, discuss your individual situation with your physician prior to using phytoestrogens or products with estrogen-modulating effects.
Paulina Nelega, RH, has been in private practice as a Clinical Herbalist for over 15 years. She has developed and taught courses in herbal medicine, and her articles on health have appeared in numerous publications. She is very passionate about the healing power of nature. Ask Dr. Jan