May 20, 2006
Vegan diet lowers odds of having twins
WASHINGTON (Reuters) - Women who eat a vegan diet -- a
strict vegetarian diet that excludes all animal products
including milk -- are one-fifth as likely as other women to
have twins, a U.S. researcher reported on Saturday.
The reason may be hormones given to cattle to boost their
milk and meat production, said Dr. Gary Steinman, an
obstetrician specializing in multiple-birth pregnancies at Long
Island Jewish Medical Center in New Hyde Park, New York.
Writing in the Journal of Reproductive Medicine, Steinman
said he compared twin births rates among women who ate a
regular diet, vegetarians who included dairy products, and
The vegans had twins at one-fifth the rate of the
milk-drinking women. Insulin-like growth factor may be
responsible, Steinman said.
All animals, including people, produce a compound called
insulin-like growth factor or IGF in response to growth
hormone. It is found in milk and it increases the sensitivity
of the ovaries to follicle stimulating hormone, thus increasing
Some studies also suggest that IGF may help embryos survive
in the early stages of development.
Vegan women have about a 13 percent lower level of IGF in
the blood than women who consume dairy.
The number of multiple births, including twins, has
increased significantly in the United States since 1975, about
the time assisted reproductive technologies were introduced.
And women are waiting until they are older to have
children, which can increase the rate of twin boths.
But Steinman thinks something else may be contributing to
the increase in the rate of twin births.
"The continuing increase in the twinning rate into the
1990s, however, may also be a consequence of the introduction
of growth-hormone treatment of cows to enhance their milk and
beef production," he said in a statement.
There could be a genetic link to IGF's influence, also,
In cattle, regions of the genetic code that control the
rate of twinning have been found close to the IGF gene.
And black women in the U.S. have, on average, the highest
rates of twin births -- and they also tend to have normally
higher levels of IGF in their blood, Steinman said.
Asian women have the lowest IGF levels and the lowest rate
of twin births and Caucasian women fall in-between, he said.
"Because multiple gestations are more prone to
complications such as premature delivery, congenital defects
and pregnancy-induced hypertension in the mother than singleton
pregnancies, the findings of this study suggest that women
contemplating pregnancy might consider substituting meat and
dairy products with other protein sources, especially in
countries that allow growth hormone administration to cattle,"