23 May 2006
Dairy Products Set Stage For Twins
An expert in multiple-birth pregnancies has found that dietary changes can affect a woman's chances of having twins, and that her overall chance is determined by a combination of diet and heredity. Obstetrician Gary Steinman carried out his study by comparing the twinning rate of vegan women, who consume no animal products, with that of women who do eat animal products. His research, published in the Journal of Reproductive Medicine, found that women who consume animal products, specifically dairy products, are five times more likely to have twins.
Steinman suspects the mechanism at work may be insulin-like growth factor (IGF), a protein that is released from the liver of animals in response to growth hormone. IGF increases the sensitivity of the ovaries to follicle stimulating hormone, thereby increasing ovulation. In agricultural animals, IGF circulates in the blood and can make its way into the animal's milk. Stein said that the concentration of IGF is about 13 percent lower in vegan women than in women who consume dairy products.
The twinning rate in the United States has increased significantly since 1975, about the time assisted reproductive technologies were introduced. "The continuing increase in the twinning rate into the 1990's, however, may also be a consequence of the introduction of growth-hormone treatment [in] cows to enhance their milk and beef production," said Steinman.
As well as a dietary influence on IGF levels, there is a genetic link in numerous species of animals, including humans. In cattle, regions of the genetic code that control the rate of twinning have been detected in close proximity to the IGF gene. Researchers have found that IGF levels are greatest among African Americans and lowest in Asians and twinning rates in these demographic groups parallel the IGF levels.
"This study shows for the first time that the chance of having twins is affected by both heredity and environment, or in other words, by both nature and nurture," said Steinman. "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," he concluded.
Source: North Shore-Long Island Jewish (LIJ) Health System