Hmm. Seems almost every woman in my family had bone density issues at an older age and and never even touched a BCP. Doc said heredity. Not disputing the claims, just sayin’.
However, this study was conducted on 107 women at West Point. As a rule, these women are going to be very healthy, and physically fit. And these are young women, so it’s clear that the bone density isn’t the result of aging. However, it does mention irregular periods, and that might be hereditary, thought I don’t know.