Dairy products linked to birth of twins
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, according to a new research.
By comparing the twinning rate of vegan women, who consume no animal products, with that of women who do eat animal products, Gary Steinman, MD, PhD, an attending physician at Long Island Jewish (LIJ) Medical Center in New Hyde Park, NY, found that the women who consume animal products, specifically dairy, are five times more likely to have twins.
The study is published in the May 2006 issue of the Journal of Reproductive Medicine, available on May 20.
The Lancet recently published an invited comment by Dr Steinman on dietary influences on twinning in the journal's May 6 issue.
The culprit may be insulin-like growth factor (IGF), a protein that is released from the liver of animals, including humans, in response to growth hormone, circulates in the blood and makes its way into the animal's milk.
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 per cent lower in vegan women than in women who consume dairy.
"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 Dr Steinman.
In the current study, when Dr Steinman compared the twinning rates of women who ate a regular diet, vegetarian diet with dairy, and vegan diet, he found that the vegan women had twins at only one-fifth the rate of women who commonly do not exclude milk from their diets.