Friday, February 5, 2016

Soy intake may insulate against the harmful effect of endocrine disruptors on infertility



soybeans 





soy-products

Bis-phenol A, or BPA, is a chemical used to make a hard clear plastic called polycarbonate, 

BPA enters our bodies mainly through  plastic water bottles, food and beverages containers and  Canned foods, because most metal cans are lined with a sealant containing BPA.

Human exposure to BPA is widespread, a survey of the U.S. population found BPA in 93 percent of urine samples from people age 6 and older.

Epidemiological and observational studies have linked BPA to various disorders including male and female infertility.

Animal data have shown that soy intake may modify the harmful effect of BPA exposure; no such human studies have been yet documented. 

According to a study published by Chavarro JE et al in The Journal of Clinical Endocrinology & Metabolism the effects of environmental toxins can be mitigated by lifestyle factors such as diet and nutrition.

This is a pilot study in humans showing interaction between soy intake and levels of BPA in urine among women undergoing ART. Experimental studies in rodents have already documented a protective effect of soy against adverse reproductive health effect of Bisphenol-A (BPA). 

These study participants were a part of an ongoing prospective cohort of women enrolled in the year 2004 to evaluate the role of environmental and nutritional determinants of fertility called as the Environment and Reproductive Health (EARTH) Study. The objective was to examine the hypothesis that soy intake modifies the association between BPA and fertility in women undergoing assisted reproduction.

The study participants consisted of 239 women, 18 to 45 years of age, and who have undergone at least one IVF cycle between  2007- 2012 at the Massachusetts General Hospital (MGH) Fertility Center, provided at least 1 urine sample for the measurement of BPA per IVF cycle, and had data on pretreatment soy food intake.

Of the women, 176 (74%) consumed soy foods. The mean isoflavone intake among soy food consumers was 3.4 mg/d.

The authors found suggestive evidence that increasing BPA levels might be the cause of lower rate of implantation (P=.02), clinical pregnancy (P=.03), and live birth rates (P=.03) only among women who did not consume soy food. Women who consumed soy food increasing BPA levels did not lead to less successful outcome in IVF.

Similarly, women who did not eat soy had the highest level of urinary BPA levels, with live pregnancy rate of  17% in contrast women with the highest level of BPA and ate soy had a pregnancy rate of 49%.

The protective effect of soy was also observed in other parameters such as markers of
oocyte and embryo quality to live birth rates.

The study results have wider ramification beyond infertility, BPA and soy. It implies that the effect of environmental chemicals and toxins can be modified by diet and nutrition.

The study did not look at how the protective effect of soy is executed, but in animal studies it was seen that BPA increases the risk of abnormal chromosomes, or can switch on and off certain gene expression and soy prevented all these actions.

The Limitations of the study are:

As the study subjects are all undergoing IVF, it is not possible to know whether the study findings can be generalized to women trying to conceive naturally.

As the intake of soy was based on study questionnaires answered by the participants it may suffer from recall and information bias.

It is important that these findings be evaluated further in larger populations, in larger studies before any recommendations can be made.

The study author also caution against a mad rush to eat soy, the study participants were consuming soy in moderation and soy itself is estrogenic and can act as endocrine disruptor itself .

References:
http://www.hazwastehelp.org/chemtoxpesticides/bisphenola.aspx

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