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Phytoestrogens, Friends or Foes?

By MD.

In order to talk about phytoestrogens, it is important to have a grasp on exactly what estrogen is. Both men and women produce estrogen, although women's bodies obviously produce more than men's bodies. Estrogen exerts an impact on the human body by locking into estrogen receptors that are located on cells that are scattered throughout the various organ systems of the body. Reproductive organs, bone tissues, brain tissue, and a variety of other organ tissues all contain cells with estrogen receptors standing sentinel to receive instructions from estrogen, a chemical messenger and hormone.

It may be surprising to some people to learn that the word “estrogen” is just a colloquial term to describe a set of hormones that function in an estrogenic manner in the body. There are a number of chemical compounds that function as “estrogen” in the body including bioidentical hormones, synthetic hormones, phytoestrogens and xenoestrogens in addition to those produced biologically by the body: estradiol, estrone, and estriol. All of these chemical compounds have an effect on cells that contain estrogen receptors. Some estrogenic chemical compounds appear to have positive effects on the health of the human body, while others appear to have negative effects.

Phytoestrogens Have Gotten Mixed Reviews. How Do Estrogens Work?

In both men's and women's bodies cell membranes in various organs have estrogen receptors. These receptors work with estrogen much like a lock and key system. The receptors function as a lock while the estrogenic chemical compounds that findtheir way into the bloodstream act like keys. Some of the non-human estrogenic compounds have a slightly different shape that can cause them to get stuck inside the lock. When that happens, these estrogens can actually block the action of our own human estrogens.

What Are Phytoestrogens?

Phytoestrogens are chemical compounds that are found in plant material. These compounds function similarly to the estrogens that are produced by the human body. Some experts believe that phytoestrogens have a negative impact on human health, while other experts assert that phytoestrogens are related to low hormone-dependent cancer rates among certain populations in the world.

Are Phytoestrogens Toxic?

Phytoestrogens in the form of herbs are sometimes used by women going through menopause to help replace the estrogens that are no longer being produced in the body. Some studies haveindicated that women who use herbal therapies and consume phytoestrogens to help relieve menopausal symptoms are more likely to experience vasomotor symptoms like hot flashes and night sweats (1). Other studies indicate that consuming phytoestrogens can increase the risk of breast cancer in women (2).

Health Benefits of Phytoestrogens

The Japanese traditional diet includes a lot more soy than the traditional American diet. In fact, the Japanese eat almost 40 times more soy products than people living in western countries. This fact, along with various other aspects of the Japanese traditional diet, have led experts to conclude that a high phytoestrogen intake can make a person healthier. In particular, epidemiological studies have shown that hormone-dependent cancers are less prevalent in both Japanese men and women (3). Many believe that the lower cancer rate has to do with high-phytoestrogen diet. Regular consumption of soy (which is high in phytoestrogens) is also related to a decreased risk of cancer (4). Experts have suggested that the mortality rates for cancer could be reduced substantially through dietary supplementation with soy products (5). Implications for phytotherapy There has been much confusion about whether phytoestrogens stimulate the development of cancer or help to prevent it. One of the major sources of confusion has been in the realm of therapeutic treatment of breast cancer.

Theoretically, all estrogens are carcinogenic (cancer-causing). Some herbalists have cautioned against recommending phytoestrogens to women who have had breast cancer because of this fact. But in reality, phytoestrogens can actually block the action (by weakly binding with estrogen receptors) of more damaging estrogens in the body, thereby reducing cancer risk (2).

Though phytoestrogens are still estrogenic compounds with the potential to work as carcinogens in the body, their function is often to limit the effects of more highly carcinogenic estrogens.

Phytotherapy, as such, appears to be a valid form of treatment to reduce the risk of breast cancer and perhaps other cancers as well. The sticky point is that phytoestrogens have estrogenic characteristics and thus, could have a corresponding carcinogenic effect on the body. However, research has shown that phytoestrogens actually protect cells from more insidious forms of estrogen; they actually reduce, rather than increase, the risk of cancer.

Phytoestrogens appear to be our friends, although research is still being conducted in the hopes that scientists will be able to better understand these compounds in the years to come.


1. Gollschewski, S., Anderson, D., Skerman, H., Lyons-Wall, P. The use of complementary & alternative medications by menopausal women in South East Queensland. Women's Health Issues 2004 Sept-Oct; 14(5); 165-71

2. Martin, P., Horwitz, K., Ryan, D., McGuire, W. Phytoestrogen Interaction with Estrogen Receptors in Human Breast Cancer Cells. Endocrinology 1978 Nov; 103(5); 1860-1867

3. Adlercreutz, H. Honjo, H., Higashi, A., et. al. Urinary excretion of lignans & isoflavonoid phytoestrogens in Japanese men & women consuming a traditional Japanese diet. The American Journal of Clinical Nutrition 1991 Dec; 54(6): 1093-100

4. Barnes, S., Peterson, T., Biochemical targets of the isoflavone genistein in tumor cell lines. Proceedings of the Society for Experimental Biology and Medicine 1995; 208(1): 103-8

5. Kennedy, A. The evidence for soybean products as cancer preventative agents. The Journal of Nutrition 1995 Mar; 125(3 suppl): 733S-43S

Joseph Raffaele

Author Joseph Raffaele received his B.A. in philosophy from Princeton University and his MD from Hahnemann University Medical School in 1989. Dr. Raffaele did his residency at The New York Hospital/Cornell University Medical Center and was formerly a clinical assistant professor of medicine at Dartmouth Medical School while in practice at the Hitchcock Clinic. Dr. Raffaele is a member of the American College of Physicians, is board certified in internal medicine, and is a diplomat of the American Board of Anti-Aging Medicine. In 1995 Dr. Raffaele began researching and developing a scientifically-based treatment program and co-founded . Since 1997 Dr. Raffaele has been exclusively focused on anti-aging medicine and bioidentical hormone replacement therapy.


Life-stages, perimenopause, treatment safety, bio-identical hormones, progesterone cream, and estriol lotion.

Epidemiologic investigations strongly support this hypothesis because the highest levels of these compounds in the diet are found in countries or regions with low cancer incidence. This report is a review on recent results suggesting that the diphenolic isoflavonoids and lignans are natural cancer-protective compounds. PMC1518863

Researchers have identified a potent phytoestrogen in hops, 8-prenylnaringenin, which has an activity greater than other established plant estrogens. PMID:10372741

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Updated: Dec 21 2013