BEIJING, May 22 (Xinhuanet) -- Scientists have discovered that drinking milk and eating cheese stimulate a protein that prompts the release of eggs and make women five times more likely to give birth to twins, according to study published in the Journal of Reproductive Medicine available Monday.

    The rate of twin births in the United States rose by more than 75 percent between 1980 and 2003. Some of the increase can be explained by the wider use of fertility treatments and women waiting longer to have children, but scientists proved that diet may play a role.

    Gary Steinman of the Long Island Jewish Medical Center in New Hyde Park, New York, carried out a simple comparison: he gathered together childbearing records for more than 1,000 vegan women who do not eat any animal products. He calculated that vegans were around five times less likely to bear twins than omnivorous women or vegetarians who eat dairy food.

    The reason may be hormones given to cattle to boost their milk and meat production, he said.

    All animals, including people, produce a compound called insulin-like growth factor, or IGF, in response to growth hormone. It is found in milk and increases the sensitivity of the ovaries to follicle-stimulating hormones, thus increasing ovulation.

    Vegan women have a 13 percent lower level of IGF in their blood than women who consume dairy products. Enditem