Chasteberry (Vitex agnus castus), also known as chaste tree, Abraham's balm, or simply as Vitex refers to the fruit of a flowering, deciduous shrub in the verbena family that is native to the Mediterranean region and now naturalized in the southeastern United States. Because its branches were once used for basket-weaving, the plant’s genus name was inspired by the Latin word vieo, which means to bind or weave. The “chaste” part of its common name stems from its use in the 11th through the 16th centuries to ensure marital fidelity, as well as to help monks to abstain from impure thoughts and impulses. The latter explains why the herb is also widely known as monk’s pepper.
The aromatic fruit, which has a pungent, peppery taste, has also been used for centuries to address menstrual irregularities, fibroids, cyclical breast pain, PMS and unpleasant symptoms of menopause, such as hot flashes and night sweats. In Germany, the standardized extract of chasteberry is routinely recommended for PMS.
How chasteberry works is not entirely understood, but research indicates that iridoid glycosides in the fruit, namely aucubin and agnoside, are responsible for providing pain relief by binding to opiate receptors. While chasteberry does not contain phytoestrogens or progesterone-like compounds, it appears to affect hormone levels by inhibiting the release of prolactin from the pituitary gland. Elevated blood levels of prolactin, so-named because it promotes lactation in mammals, is associated with PMS, menstrual irregularities and cyclical breast pain.
Chasteberry is taken as a tincture, or as an infusion (tea) made from the crushed fruit. Beyond rare allergic reactions in the form of rash or itchy skin, there are no significant side effects associated with this herb. However chasteberry is not recommended for pregnant or nursing women due to its hormonal effects.