What’s the role of soy in uterine fibroids?

Thanks to soy’s close relationship to estrogen, there has been a lot of discussion about its impact on women’s health and, in particular, its relationship to the development of uterine fibroids. A recent overview of current research published in Nutrition & Cancer1 demonstrates the mixed conclusions that have been reached on this subject.

Soy and estrogen

The reasons that soy has been studied so closely is that it contains plant estrogens called isoflavones, which are a weaker form of the estrogen found in people. The hope is that these isoflavones can protect against hormonal diseases such as breast cancer.However, because uterine fibroids respond to a woman’s levels of estrogen and progesterone, the concern is that soy can make fibroids and symptoms of fibroids worse.

Soy and fibroid adult studies

Here is a look at the most relevant studies regarding the impact of soy on uterine fibroids.

  • A Chinese case-control study – This study used validated, self-administered questionnaires to look at participants’ lifestyles, including diets. The study included 73 women who had fibroids and 210 women who did not. The study concluded that eating soy did not contribute to uterine fibroids or fibroid symptoms in any women.1,2
  • A Japanese cross-sectional study – This study examined the lifestyles of 285 premenopausal Japanese women. It concluded that soy did not contribute to uterine fibroids or fibroid symptoms.1,3
  • The Black Women’s Health Study – This large study of 22,120 premenopausal women in the United States indicated that eating soy did not increase the symptoms of fibroids or the occurrence of fibroids in women.1,4

Fibroids and consumption of soy in infancy – SELF

The studies on adult woman indicate that soy can safely be consumed without increasing one’s risk of developing uterine fibroids.

But can soy intake in childhood lead to the development of fibroids adulthood? Here is a look at some studies that asked this question.

  • Study of Environment, Lifestyle & Fibroids (SELF) – This is an ongoing cohort study of 1,696 African American women ages 23-34 years. SELF looked at 1,553 women who had consumed soy while they were babies.5 The study found that 22 percent had fibroids, but only 13 percent had consumed soy formula as babies. Overall, the results did not indicate any relationships between consuming soy formula as an infant and developing fibroids later in life.5

There was one feature noted by researchers in this study that indicated a potential correlation between soy intake and symptoms of fibroids: Those women who had consumed soy formula as infants and had fibroids suffered from larger fibroids than those who had not. Specifically, their largest fibroid was 32 percent larger and their total fibroid volume was 127 percent more.The conclusion of the researchers in this study was that consuming soy early in life can impact a developing uterus.5

Fibroids and consumption of soy in infancy – additional studies

  • Animal studies – The SELF findings are supported by animal studies that show that baby animals exposed to genistein (a soy isoflavone) suffer impacts on their uteruses.6
  • Black Women’s Health Study – After 12 years, the study reported that 7,268 women had fibroids bu that “there was little evidence of an association between [fibroids] and…exposure to soy formula in infancy.” Further, “these findings do not support the hypothesis that intrauterine and early life factors are strongly related to [fibroid] risk.”7

These studies indicate that there is no definitive answer about the impact of soy consumption on fibroids or symptoms of fibroids. However, it appears that soy may only have a negative impact in infancy, without causing problems in grown women.

Viva Eve: The Fibroid Experts

Whatever the cause of fibroids, they can be painful and cause discomfort and curtail normal functioning.

At Viva Eve we provide high-quality, personalized fibroid diagnosis and treatment for every patient we see. We will partner with you to determine the best way to treat your problematic fibroids.

Sources for information referenced in this post

  1. Parazzini, F., Di Martino, M., Candiani, M., et al. (2015). Dietary components and uterine leiomyomas: a review of published data. Nutr Cancer, Mar; 67(4): 569-579.
  2. He, Y., Zeng, Q., Dong, S., et al. (2013). Associations between uterine fibroids and lifestyles including diet, physical activity and stress: a case-control study in China. Asia Pac J Clin Nutr, 22(1): 109-117.
  3. Negata, C., Nakamura, K., Oba, S., et al. (2009). Association of intakes of fat, dietary fibre, soya isoflavones and alcohol with uterine fibroids in Japanese women. Br J Nutr, May; 101(10): 1427-1431.
  4. Wise, L., Radin, R., Palmer, J., et al. (2010). A prospective study of dairy intake and risk of uterine leiomyomata. Am J Epidemiol, Dec; 171(2): 221-232.
  5. Upson, K., Harmon, Q., & Baird, D. (2016). Soy-based infant formula feeding and ultrasound-detected uterine fibroids among young African-American women with no prior clinical diagnosis of fibroids. Environ Health Perspect, Nov; 124(6): 769-775.
  6. Greathouse, L., Bredfeldt, T., Everitt, J. (2012). Environmental estrogens differentially engage the histone methyltransferase EZH2 to increase risk of uterine tumorigenesis. Mol Cancer Res, Apr; 10(4): 10.1158/1541-7786.MCR-11-0605.
  7. Wise, L., Radin, R., Palmer, J., et al. (2012). Association of intrauterine and early life factors with uterine leiomyomata in black women. Ann Epidemiol, Dec; 22(12): 847-854.77

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