There is no scientific evidence to support the claim that eating soybeans or soya can increase breast size. In fact, the idea that soy can increase breast size is a myth.
Soybeans and soya products, such as tofu, are a good source of protein and contain isoflavones, which are compounds with weak estrogen-like activity. Some people believe that these compounds can increase breast size, but there is no scientific evidence to support this claim.
Breast size is determined by a combination of genetic, hormonal, and environmental factors. Hormonal changes, such as those that occur during puberty and pregnancy, can cause changes in breast size, but consuming soybeans or soya products is not likely to have a significant impact on breast size.