Women who have a high intake of animal products, specifically dairy, are five times more likely to have twins, but it can be modified by certain dietary changes, finds a study.
Gary Steinman, an obstetrician who is well known for his care and research in multiple birth pregnancy, compared the twinning rates of women who ate a regular diet, vegetarian diet with dairy, and vegan diet, reported the science portal EurekAlert.
The culprit may be insulin-like growth factor (IGF), a protein that is released from the liver of animals, including humans, as a response to growth hormones. It circulates in the blood and makes its way into the animal’s milk, said Steinman.
IGF increases the sensitivity of the ovaries to follicle stimulating hormone, thereby increasing ovulation. Some studies also suggest that IGF may help embryos survive in the early stages of development. The concentration of IGF in the blood is about 13 percent lower in vegan women than in women who consume dairy.
The twinning rate in the US has increased significantly since 1975. The intentional delay of childbearing has also contributed to the increase of multiple-birth pregnancies, since older women are more likely to have twins, he noted.
“The continuing increase in the twinning rate into the 1990’s, however, may also be a consequence of the introduction of growth-hormone treatment of cows to enhance their milk and beef production,” said Steinman.
The researcher also found that vegan women had twins at only one-fifth the rate of women who commonly do not exclude milk from their diets, according to the study published in the May 2006 issue of the Journal of Reproductive Medicine.
“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,” Steinman pointed out.
The obstetrician also found that women who become pregnant while breastfeeding are nine times more likely to conceive twins than women who are not breastfeeding at the time of conception.
However, he was quick to add that dietary changes could influence a woman’s chances of having twins.