What are phytoestrogens?

Phytoestrogens are a group of chemicals found in plants that can act like the hormone estrogen. Estrogen is a hormone necessary for childbearing and is involved with bone and heart health in women. However, higher exposure to estrogens over a lifetime is linked with increased breast cancer risk.

How do phytoestrogens act in the body?

There are many different ways that phytoestrogens may work in the body. The chemical structure of phytoestrogens is similar to estrogen, and they may act as mimics (copies) of estrogen. On the other hand, phytoestrogens also have effects that are different from those of estrogen.

Working as estrogen mimics, phytoestrogens may either have the same effects as estrogen or block estrogen's effects. Which effect the phytoestrogen produces can depend on the dose of the phytoestrogen. The phytoestrogen can act like estrogen at low doses but block estrogen at high doses. Estrogen activates a family of proteins called estrogen receptors. Recent studies have shown that phytoestrogens interact more with some members of the estrogen receptor family, but more information is needed about how these receptors work, especially in breast cancer. Finally, phytoestrogens acting as estrogen mimics may affect the production and/or the breakdown of estrogen by the body, as well as the levels of estrogen carried in the bloodstream.

Phytoestrogens - acting differently from estrogen - may affect communication pathways between cells, prevent the formation of blood vessels to tumors or alter processes involved in the processing of DNA for cell multiplication. Which of these effects occur is unknown. It is very possible that more than one of them may be working. Also, the effects in various parts of the body may be different.

What foods contain phytoestrogens?

More than 300 foods have been shown to contain phytoestrogens. Most food phytoestrogens are from one of three chemical classes, the isoflavonoids, the lignans or the coumestans. Isoflavonoid phytoestrogens are found in beans from the legume family; soybeans and soy products are the major dietary source of this type of phytoestrogens. Lignan phytoestrogens are found in high fiber foods such as cereal brans and beans; flaxseeds contain large amounts of lignans. The coumestan phytoestrogens are found in various beans such as split peas, pinto beans, and lima beans; alfalfa and clover sprouts are the foods with the highest amounts of coumestans.

Phytoestrogen related articles:
Phytoestrogen food sources
Estrogens: What they are, functions, and synthesis
Soy phytoestrogens, osteoporosis and menopausal women
Lignan: food sources
Flax seed, pregnancy, and menopause

Pregnancy, health and nutrition related articles:
Caffeine use during pregnancy
Antidepressant use during pregnancy
Pregnancy, breast feeding and bone health
Fish oil health benefits during pregnancy and for child development
Vitamin E intake during pregnancy and its effect on childhood asthma
Flax seed, pregnancy, and menopause

Articles of interest:
Erectile dysfunction, and benefits of L-arginine and nitric oxide
L-arginine: food sources, health benefits, and side effects

Excerpted from: Phytoestrogens and Breast Cancer by Barbour S. Warren Carol Devin., Program on Breast Cancer and Environmental Risk Factors in New York State.