There may be ways women can protect themselves, according to Dr. Yaffe. "We don't completely know what causes density, but we certainly think it's related to some extent to diet. It's suggested that a high fat diet may actually be partially responsible for breast density," he said.
Breast tissue becomes less dense as women age. It's important to note the researchers do not say younger women are at an increased risk of breast cancer because of their dense breast tissue. The researcher compared women of similar ages to each other. Young women who have denser breast tissue than other women of the same age would have a higher risk of developing breast cancer.