Some people say that consuming soy beans or soy bean products while pregnant can lead to birth defects such as hypospadia. Is this true? What does the most recent research say?
This is an interesting one ! My reading of the research on this matter is that the main area of concern is not the consumption of soy itself. It is the consumption of genetically modified soy that is resistant to "Roundup" - the most widely used herbicide globally, of which the main active ingredient is glyphosate. This is toxic and carcinogenic, and worryingly, the additives (adjuvants) commonly used with it are even more toxic.
I believe the link between soy and birth defects originated with 2010 Rusian language animal study by Surov and colleagues, which was widely reported on at the time and found a strong link between GMO soy consumption and birth defects (and tumor development) in rats over 2 years. However, I found no information about peer review, or details about the study design. It cannot be found on PubMed or Google Scholar, and so it is difficult to give much weight to this study.
Séralini et al (2012) looked at genetically modified corn, where where 3 groups of 10 hamsters were studied over a period of 2 years, and also found results confirming the link . This attracted enormous attention at the time, and several eminent biologists and statisticians including Professor Sir David Spiegelhalter were deeply critical of the methods used. The article was subsequently retracted at the request of the journal, which is very worrying because this occurred shortly after the editor-in-chief of the journal was replaced by a former employee of Monsanto, the US agribusiness giant, whose genetically modified soy was used in the study!!! It was subsequently re-published in 2014 in Environmental Sciences Europe, again to much criticism.
But, as to the current status of the literature on the subject, De Araujo et al (2016) conducted a systematic review of studies investigating the link between pesticides and birth defects and concluded:
Current epidemiological evidence, albeit limited to a few studies using non-quantitative and indirect estimates and dichotomous analysis of exposures, does not lend support to public concerns that glyphosate-based pesticides might pose developmental risks to the unborn child. Nonetheless, owing to methodological limitations of existing analytical observational studies, and particularly to a lack of a direct measurement (urine and/or blood levels), or an indirect estimation of exposure that has proven valid, these negative findings cannot be taken as definitive evidence that GLY, at current levels of occupational and environmental exposures, brings no risk for human development and reproduction.
Williams et al (2012) conducted a critical review of existing studies on the link between birth defects and glyphosate and found:
no consistent effects of glyphosate exposure on reproductive health or the developing offspring
As for hypospadia in particular, Carmichael et al (2013) found a protective effect from phytoestrogens.
To sum up, there is insufficient evidence of a link between GMO soy and birth defects in humans despite some animal studies confirming the link and the World Health Organisation classifying glyphosate as "probably carcinogenic to humans". One explanation for this is that animals are fed massive amounts of the substance being studied, but humans have such relatively low exposure. A recent article by Avila-Vazquez et al (2018) looked at the rate of birth defects in an agricultural town in Argentina in the heart of the GMO soy and corn growing areas found:
The spontaneous abortion and congenital abnormalities rates are three and two times higher than the national average reported by the national health (10% vs. 3% and 3% - 4.3% vs 1.4% respectively)
In short: it appears that there is very little to worry about at the present time, unless:
- You live on GMO soy, or
- You live in an area where GMO soy is grown extensively.
Avila-Vazquez, M. , Difilippo, F. , Lean, B. , Maturano, E. and Etchegoyen, A. (2018) Environmental Exposure to Glyphosate and Reproductive Health Impacts in Agricultural Population of Argentina. Journal of Environmental Protection, 9, 241-253 https://doi.org/10.4236/jep.2018.93016
Carmichael, S. L., Cogswell, M. E., Ma, C., Gonzalez-Feliciano, A., Olney, R. S., Correa, A., … the National Birth Defects Prevention Study. (2013). Hypospadias and Maternal Intake of Phytoestrogens. American Journal of Epidemiology, 178(3), 434–440. http://doi.org/10.1093/aje/kws591
De Araujo, J. S., Delgado, I. F., & Paumgartten, F. J. (2016). Glyphosate and adverse pregnancy outcomes, a systematic review of observational studies. BMC public health, 16, 472-472. https://dx.doi.org/10.1186%2Fs12889-016-3153-3
Séralini, G.E., Clair, E., Mesnage, R., Gress, S., Defarge, N., Malatesta, M., Hennequin, D. and De Vendômois, J.S., 2012. RETRACTED: Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Food and Chemical Toxicology, Volume 50, Issue 11,2012,Pages 4221-4231,ISSN 0278-6915, https://doi.org/10.1016/j.fct.2012.08.005.
Séralini, G.E., Clair, E., Mesnage, R., Gress, S., Defarge, N., Malatesta, M., Hennequin, D. and de Vendômois, J.S., 2014. Republished study: long-term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Environmental Sciences Europe, 26(1), p.14. https://doi.org/10.1186/s12302-014-0014-5
Williams, A. L., Watson, R. E., & DeSesso, J. M. (2012). Developmental and reproductive outcomes in humans and animals after glyphosate exposure: a critical analysis. Journal of Toxicology and Environmental Health, Part B, 15(1), 39-96. https://doi.org/10.1080/10937404.2012.632361