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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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