Fibroids, or uterine leiomyomas, common benign tumors that form in the wall of the uterus, are a principal cause of hysterectomy in women of child-bearing age. Like most tissues in your body, the cells in your uterus respond to hormonal stimulation, and fibroids grow larger when estrogen is present. Many foods contain estrogen-like compounds called phytoestrogens, and some of these substances may contribute to the growth of uterine fibroids.
Weak Estrogenic Effects
In his book, “A Maverick of Medicine Speaks to Women,” Dr. Duane Townsend notes that more than 300 plants contain phytoestrogens, and all of these compounds exert weak estrogenic effects in your body. In premenopausal women, phytoestrogens compete with and reduce the effects of your own estrogens. Following menopause, phytoestrogens can replace your dwindling estrogen levels, thereby easing many of the unpleasant symptoms associated with menopause. The isoflavones found in soy, genistein and daidzein, have been widely studied.
Receptors
Hormones influence fibroid growth by stimulating receptors in the cells of the tumors. Two types of estrogen receptors, ER-alpha and ER-beta, are found in fibroids. According to scientists at the National Institute of Environmental Health Sciences, genistein, the principal isoflavone in soy, attaches more readily to ER-beta. However, stimulation of either receptor appears to enhance the growth of uterine fibroids.
Conflicting Results
As with many plant-based compounds, research surrounding phytoestrogens has produced conflicting results. For example, a study published in the August 2008 issue of “Human Reproduction” showed that low concentrations of genistein stimulated the growth of human leiomyoma cells grown in culture. Another study, published a year earlier in the same journal, reported that higher concentrations of genistein suppressed the growth of culture-grown fibroid cells. The authors of the 2007 study contended that genistein’s impact on fibroid growth is concentration-dependent and remarked that it may not be possible to consume enough soy to achieve fibroid-shrinking blood levels of genistein.
Not All Phytoestrogens Are Equal
Phytoestrogens can act as weak estrogens or as anti-estrogens, depending on your circulating estrogen levels and the types of receptors found in a specific tissue. The type of phytoestrogen may also play a role in its effects on a given organ. Uterine fibroids appear to be stimulated by some phytoestrogens, such as those found in soy. Other, lesser-known phytoestrogens, such as lignans from flaxseed, may help reduce fibroid growth. An epidemiological study published in the September 2006 issue of “The American Journal of Clinical Nutrition” showed that women who consumed more lignans had a slightly lower incidence of symptomatic fibroid tumors.
Considerations
Even though they are benign, uterine fibroids often lead to hysterectomy among women in the United States. Fibroids frequently cause bleeding and pelvic pain, and they can grow to a size that interferes with the function of other organs. It is not clear what effects phytoestrogen-rich foods have on uterine fibroids, probably because different phytoestrogens exert different effects, and a single phytoestrogen can either induce or inhibit fibroid growth, depending on its concentration in your bloodstream. However, there is some evidence that certain phytoestrogens can cause fibroids to grow larger. If you have fibroids, ask your doctor if consumption of estrogen-containing foods is appropriate for you.
References
- “Human Reproduction”; A Low Concentration of Genistein Induces Estrogen Receptor-Alpha and Insulin-Like Growth Factor-1 Receptor Interactions and Proliferation in Uterine Leiomyoma Cells; X. Di, et al.; August 2008
- “A Maverick of Medicine Speaks to Women”; Duane Townsend, M.D. and Rita Elkins, M.H.; 2003
- “Human Reproduction”; Stimulatory and Inhibitory Effects of Genistein on Human Uterine Leiomyoma Cell Proliferation Are Influenced by the Concentration; A.B. Moore, et al.; October 2007
- “The American Journal of Clinical Nutrition”; Lignan and Isoflavone Excretion in Relation to Uterine Fibroids: A Case-Control Study of Young to Middle-Aged Women in the United States; C. Atkinson, et al.; September 2006
