Eating milk and other dairy products could increase a woman’s chance of having twins, a US doctor is proposing, based on a study of vegan women.
The rate of twin births in the United States rose by more than 75% between 1980 and 2003. Some of this can be explained by the use of fertility treatments, which ups the risk of multiple births. But that can’t explain all of the jump, researchers say. Bearing twins is more risky for both mother and child than having a single baby, so scientists want to know what’s causing the rise.
Steinman suggests that the difference in the rate of twin production boils down to the difference in diet. He suggests that animal-product foodstuffs, in particular dairy foods, could boost the production of a protein called insulin-like growth factor (IGF) in women. This could promote the release of eggs by the ovary, so that two are more likely to be fertilized at the same time. There has been an increased use of growth hormones in dairy cows, he says, which may have had an impact on this.
The hypothesis is interesting, says Paul Haggerty who studies nutrition, fertility and disease at the Rowett Research Institute in Aberdeen, UK, but there are other reasons that vegan women might bear twins less frequently, he points out. Milk-drinking women could tend to be fatter or better nourished - and heavier women are also more likely to bear twins. Alternatively, there might be other nutrients that vegan women lack.
It is premature for women to change their diet in order to decrease their risk of having twins, Haggerty says: “There are a number of loose ends here.”