Vitex, or Vitex agnus-castus is an herbal supplement which has various effects upon the reproductive systems of both men and women. Vitex has been used throughout history to actually reduce the sex drive of both men and women, and is also known as chaste tree, chaste berry, and monk's pepper.

Native to the Mediterranean, vitex is also grown on the East Coast of the United States. The plant produces black peppercorn-like berries, which were used by ancient Romans. Medieval monks and priestesses ate vitex berries to aid them in keeping their vows of chastity. In addition, vitex was used in the ancient Roman world to both stop women from hemorrhaging after childbirth and to increase the milk supply of nursing mothers.

Vitex may help in treating PMS, insufficient milk supply in nursing women, irregular menstrual cycles, and decreasing male sex drive. Vitex works by acting on the pituitary gland, increasing production of luteinizing hormone (LH) and decreasing follicle stimulating hormone (FSH). This results in decreasing androgens — male hormones — and increasing progesterone levels.

The herb can also regulate the hormone prolactin, which affects the production of milk in nursing women, uterine fibroids, and premenstrual breast tenderness. Vitex changes the level of hormones, reducing breast pain and bloating associated with PMS, and increasing milk supplies in nursing mothers.

Vitex has been studied in Europe, with women in the study reporting improvement of PMS symptoms and an increase of milk supply. There is anecdotal evidence of vitex effectively regulating the menstrual cycle and easing the pain of menstrual cramps. In reducing the level of androgens, vitex may clear up acne, reduce sex drive in men, and treat women with hirsitism, or abnormal hair growth.

Available in tinctures and capsules, vitex can be found at health food stores and on the Internet. The only side effects known to be associated with vitex are nausea and a rash. Vitex is generally taken daily for three to six months, but should not be used by children or pregnant women. As vitex can decrease fertility in men, this should also be taken into consideration. As with any supplements, you should always talk to your doctor to make sure that the herbs do not interact with any other medications that you may be taking.