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[SANET-MG] my grandmother aways said "you are what you eat"
Environmental Health Perspectives Volume 114, Number 4, April 2006
Color by Soy
Genistein Linked to Epigenetic Effects
There is substantial evidence that a pregnant mother's exposure to
environmental substances can affect her young. Now researchers have
uncovered the first direct evidence that maternal exposure to a
phytoestrogen in soy can cause lifelong epigenetic changes--that is,
changes in gene activity from processes other than changes in the DNA
sequence--in mouse offspring [EHP 114:567-572; Dolinoy et al.]. If the
findings hold up, there eventually could be repercussions in several
important arenas, including recommendations about what pregnant women
and infants should eat.
Telltale traits. Differences in the size and color of offspring are
epigenetic effects of genistein consumption (via a high-soy diet) by
image: Dolinoy et al.
The researchers made their observations in genetically identical yellow
mice. The mothers in the test group ate a diet modified to include a
concentration of genistein typical of what people eating a high-soy diet
would consume, while the control group mothers ate the same food without
the genistein. The diets began two weeks before mating and continued
through pregnancy and lactation. At 21 days after birth, the offspring
were weaned to a stock maintenance diet, which they ate for the rest of
the study period.
The researchers assessed offspring coat color and body weight, traits
that can vary with methylation (a mechanism in which methyl groups
attach to DNA where cytosine bases occur consecutively). The offspring
exhibited wide color differences, ranging from yellow to brown, with
varying degrees of mottling in between. The researchers found that these
differences corresponded closely with methylation in a DNA region
upstream of the offspring's Agouti gene, which determines coat color.
The 44 genistein-fed offspring were more than twice as likely as the 52
controls to have brown fur and to have much higher methylation, while
they were only one-third as likely to have yellow fur and much lower
methylation. Animals that had a blend of yellow and brown fur had
progressively increased methylation as brown became more dominant.
For weight gain, the brown mice showed by far the least propensity to
become overweight. The other groups, with yellow or various combinations
of yellow-brown fur, had roughly the same trend toward becoming
significantly overweight. The researchers also found that methylation
was evident in many parts of the body, including the brain, liver,
kidney, and tail.
The team speculates that the ability of genistein to increase DNA
methylation provides a plausible explanation for the lower incidence of
certain cancers in Asians compared to Westerners. Nevertheless, the
pathway by which these changes occurred suggests there could also be
significant adverse interactions between genistein and common dietary
supplements such as folic acid, which is added to many foods and
recommended for pregnant women. Soy-based infant formulas might also be
a concern because of the high levels of genistein present in these
products. More research is needed to determine if these worrisome
possibilities are correct.
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