A review article that looked at three studies covering 86,881 patients. The use of natural progesterone was associated with a significantly lower risk of breast cancer compared with synthetic progestins. Physicians should have no hesitation prescribing natural progesterone, as the evidence is clear that progesterone does not cause breast cancer. Indeed, progesterone is protective and preventative of breast cancer. In addition, the use of progesterone has been linked to lower rates of uterine and colon cancers and may also be useful in treating other cancers such as ovarian, melanoma, mesothelioma, and prostate. Progesterone may also be helpful in preventing cardiovascular disease and preventing and treating neurodegenerative conditions such a stroke and traumatic brain injury.