But cholesterol is just one of many contributors to vessel clogging. Some studies suggest its benefits even extend to protecting against Alzheimer's disease. According to a 1998 study conducted at Mt. Sinai Hospital in New York, a dwindling number of cells in the hippocampus is linked to low estrogen levels. The hippocampus is a region of the brain involved with memory. But estrogen replacement therapy carries risks, too.
Studies show it can increase the risk of breast cancer and endometrial cancer.
That's because the hormone can fuel the rampant growth of abnormal cells in some tissues. And, elevated levels of the hormone can block the effects of tamoxifen, a powerful, but controversial cancer drug that has been used for 20 years in advanced cases of breast cancer and other forms of cancer.