You might have heard that papaya can help lower your hormone levels--for instance, your estrogen. Whether that's an effect you'd encourage or one you'd prefer to avoid, there's no scientific evidence to suggest that papaya enzyme has any effect upon estrogen--nor any other hormone, for that matter.
The estrogen hormone is one of the female reproductive hormones. It helps increase the thickness of the lining of the uterus each month, in preparation for implantation of a fertilized egg. If you don't conceive, the tissue in your ovaries that secretes estrogen deteriorates, and your estrogen levels fall. This causes sloughing of the uterine lining--a menstrual period, explains Dr. Lauralee Sherwood in her book "Human Physiology."
Because estrogen is associated with fertility, it might seem counterintuitive to want to lower it. However, high estrogen is associated with breast cancer risk, particularly with the risk of breast cancer recurrence, reports ScienceDaily.com. It's important to note, though, that the relationship is purely correlational; no studies have proven that high estrogen causes breast cancer, and it's entirely possible that recurrence of cancer causes high estrogen levels.
Papaya enzyme, called papain, is a proteolytic or protein-digesting enzyme that has great utility as an ingredient in meat marinades because it tenderizes tough cuts. While it's rumored to have many positive health effects, there's little scientific evidence to back up any of the conjecture. For instance, there's no evidence linking papaya enzyme to reduction of estrogen levels. If you're concerned about your estrogen, you should talk to your health care professional.
There are several reasons papaya enzymes can't affect estrogen. First, your stomach acid breaks down papaya enzyme when you consume it. Second, enzymes can only each participate in one type of reaction. Papain, therefore, can't do anything but break down protein, which has no impact upon estrogen production. Finally, there's no evidence that the human body has any mechanism for taking up enzymes into the cells from the digestive tract.