Soy Consumption May Enhance Female Fertility

Soy, BPA & Female Fertility

Soy is a widely consumed food item. Now new research published in the Journal of Clinical Endocrinology & Metabolism suggests that women undertaking fertility treatment may benefit from eating more soy based foods.

It is thought that soy can protect the body from the harmful effects of the chemical bisphenol A (BPA). This toxin is widely used in food containers, water bottles, and other plastic packaging.

BPA and hormones

BPA is a synthetic colourless compound with limited water solubility. BPA is soluble in organic solvents and has been used in commercial applications since the late 1950s. BPA is widely used in epoxy resins and plastics. Of all the synthetic chemicals produced in the world, BPA is one of the most common and is manufactured in massive volumes.

Plastics made using BPA are clear and very strong. Consequently this is a popular component of items such as drink bottles and storage containers. Water pipes and food and beverage cans are often lined with BPA-based epoxy resins. As a result, most people are regularly exposed to BPA on a daily basis.

Over recent years there have been growing concerns surrounding the safety of BPA and how this chemical impacts on human health. The subject of extensive research, BPA exhibits hormone-like properties. This chemical acts as a synthetic estrogen. BPA bines to estrogen receptors in the body and induce transactivation of the estrogen-responsive genes[1. “Safe, S. et.al. (2001). Toxicology of environmental estrogens. Reproduction, Fertility and Development. Volume 13, Issue 4, (pp. 307-15).”].

However, authorities such as the United States Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) maintain that BPA is found in such low quantities in foods that it doesn’t pose a threat. Nevertheless, the EFSA does acknowledge that there are many unknown factors and more research is necessary.

In the United States reports from the Centres for Disease Control and Prevention (CDP) suggest that approximately 96% of Americans have BPA present in their body. Animal studies have shown that high levels of BPA in the body can cause reproductive and developmental alterations[2. “Ema, M. et.al. (2001). Rat two-generation reproductive toxicity study of bisphenol A. Reproductive  Toxicology. Volume 5, (pp. 505-23).”], [3. “Tyl, R. et.al. (2002). Three-generation reproductive toxicity study of dietary bisphenol A in CD Sprague-Dawley rats. Toxicology Science. Volume 68, Issue 1, (pp. 121-46).”]. Other studies have found that even at low doses BPA can negatively affect reproductive health and neurodevelopment[4. “European Commission. (2003). 4,4’-Isopropylidenediphenol (Bisphenol-A) Summary Assessment Report. Joint Research Centre Institute of Health and Consumer Protection. Ispra, Italy.”], [5. “Gray, G. et.al. (2004). Weight of the evidence evaluation of low-dose reproductive and developmental effects of bisphenol A. Human Ecology Risk Assessment. Volume 10, (pp. 875-921.)”], [6. “Wilson, N. et.al. (2007). An observational study of the potential exposures of preschool children to pentachlorophenol, bisphenol-A, and nonylphenol at home and daycare. Environmental Research. Volume 103, Issue 1, (pp. 9-20.”).], [7. “Witorsch, R. (2002). Low-dose in utero effects of xenoestrogens in mice and their relevance to humans: an analytical review of the literature. Food Chemical Toxicology. Volume 40, Issue 7, (pp. 905-12.)”], [8. “Akingbemi, B. et.al. (2004). Inhibition of testicular steroidogenesis by the xenoestrogen bisphenol A is associated with reduced pituitary luteinizing hormone secretion and decreased steroidogenic enzyme gene expression in rat Leydig cells. Endocrinology. Volume 145, (pp. 592-603).”], [9. “Leranth, C. et.al. (2008). Bisphenol A prevents the synaptogenic response to testosterone in the brain of adult male rats. Endocrinology, Volume 149, (pp. 988-94.)”], [10. “Timms B. et.al. (2005). Estrogenic chemicals in plastic and oral contraceptives disrupt development of the fetal mouse prostate and urethra. Proceedings of the National Academy of Science USA. Volume 102, Issue 19, (pp. 7014-19.)”].

The ability of BPA to mimic estrogen has health implications. How dangerous this chemical is remains to be fully determined.  Nevertheless, studies do urge caution and it’s possible that BPA may adversely affect fertility. This is particularly concerning for women undertaking fertility treatments such as IVF.

Soy may prevent the negative effects of BPA

In recent years soy-based foods have been recommended to help protect people against high cholesterol, heart disease, cancer, and osteoporosis. Soy is also thought to help with weight loss and minimise the severity of hot flushes.

Soy beans are enriched with isoflavones. These are plant-derived estogens called phytoestrogen. Like BPA, these phytoestrogens are also endocrine disruptors. However, unlike BPA, phyoestrogens are not estrogen agonists once they are bound to receptors.

The effects of phyoestrogens on human health is a controversial topic[11. “Patisaul, H. and Jefferson, W. (2010). The pros and cons of phytoestrogens. Front Neuroendocrinology. Volume 31, Issue 4. (pp. 400-19).”]. However, new research suggests that soy consumption may counteract the negative reproductive effects of BPA exposure.

IVF treatment success bolstered by soy intake

Dr. Jorge E. Chavarro and colleagues recently published their findings of new study investigating the relationship between diet, BPA exposure, and IVF success[12. “Chavarro, J. et.al. (2016). Soy Intake Modifies the Relation Between Urinary Bisphenol A Concentrations and Pregnancy Outcomes Among Women Undergoing Assisted Reproduction. The Journal of Clinical Endocrinology & Metabolism. Ahead of Press” ]. Believed to be the first study to show an interaction between BPA and soy in humans, the results of this research may have implications for future IVF treatments.

In this study researchers focused on 239 women receiving IVF treatment at the Massachusetts General Hospital Fertility Center between 2007 and 2012. The women aged between 18 and 45 were participating in the Environment and Reproductive Health (EARTH) Study. This is an ongoing cohort study examining how nutrition and environmental factors influence fertility.

Chavarro and colleagues determined participants BPA exposure by measuring concentrations of this chemical in urine. The women completed a lifestyle questionnaire to assess the frequency of soy-based food consumption. Among the participants a total of 176 women consumed soy foods.

The researchers found that women with higher levels of BPA in their urine and who did not eat soy foods had lower rates of embryo implantation and fewer live births compared with women with lower BPA levels in their body. Conversely, the concentration of BPA had no impact on the outcome of IVF treatments in women who routinely consumed soy-based foods.

What do these findings mean for women trying to conceive?

It’s recommended that women trying to have a baby should minimise BPA exposure as much as possible while trying to conceive and during pregnancy. However, due to the widespread use of this chemical it is difficult to avoid completely.

This new research suggests that a diet containing soy-based foods may modify the risks of BPA exposure. While more research is necessary to better understand the relationship between soy and BPA, the preliminary findings are positive.

Soy-based foods

In addition to plain soy beans, there are plenty of soy-based foods. These can include flour, milk, oil, and yogurt. There are many tofu varieties and different fermented soy foods.

Like all food types, consume soy in moderation. Always look for soy beans or soy-based products that are organic and GMO free whenever possible.

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