Did you know that the rate of twin births in the United States increased by 32% between the years of 1992 and 2001?
Plenty of factors affect the rate of twinning, including genetics, the mother's age, her weight, and the use of reproductive technology. Interestingly though, a study revealed that omnivores and vegetarians were five times more likely to give birth to twins than vegans, who don't consume any animal products whatsoever. Vegan women also had 13% lower concentrations of a hormone called insulin- like growth factor, or IGF. Earlier research has demonstrated that IGF increases the incidence of a woman's ovary releasing multiple eggs at once. The connection to diet? The liver releases IGF in response to growth hormone. All cow's milk contains bovine growth hormone. It's naturally released by the cow's pituitary gland. The research is preliminary so far, but there appears to be a connection between twinning and consuming dairy.
In order to increase milk production, numerous U.S. dairy farms have been injecting their cows with the hormone since the mid-nineties. A noteworthy side effect is that cows with higher growth hormone levels also produce more twins.
The hypothesis is that the additional growth hormone in some American dairy products could potentially explain part of the remarkable increase in the rate of twinning in humans?
That's what the evidence suggests, but more research needs to be done before women wanting children let it influence their grocery lists.