Diet and Twins
Over the last three decades or so, the number of twin births has multiplied by three. Researchers first thought the trend had to do with the number of in vitro fertilization procedures (IVF) or the fact that women were having babies later in life. However, in the middle of the last decade, doctors began to limit the number of embryos transferred during the course of in vitro fertilizations. Even though the number of embryos transferred was reduced, the number of twin births continued to rise. Now, it seems, researchers have found evidence that bovine growth hormones, present in our food supply, may be behind the abundant number of twin births.
Omnivores Versus Vegans
Dr. Gary Steinman of Long Island Jewish Medical Center and his colleagues looked at the number of twin births in relation to maternal diet. Participants were divided into those who ate meat or milk and those who abstained from these food sources. Those moms who were omnivores or vegetarians and included milk or meat in their diets had an incidence of twin births five times that of the vegan moms, who ate no food derived from animals or their byproducts.
Steinman's report, published in the Journal of Reproductive Medicine suggests that growth factor, present in a protein resembling insulin that is released by the liver as a response to bovine growth hormone, may be responsible for the surge in twin births. Previous studies have shown that this protein increases ovulatory function and remains in the body even after the food source, for instance milk, has been digested. A daily glass of milk over a period of 12 weeks raised the protein levels of the body by a full 10%. The blood of vegan women has a 13 percent reduction in the concentration of this protein.
Banned in the UK
In another scientific journal, The Lancet, Steinman noted the fact that bovine growth hormone is banned in the U.K. In spite of this, the twin birth rate rose there by 16 percent between the years 1992 and 2001. Perhaps more remarkable is the fact that during this same period, the twinning rate increased by 32 percent in the United States, where the substance is not banned. Steinman comments, "This study shows for the first time that the chance of having twins is affected both by heredity and environment, or in other words, by both nature and nurture."