Chaste tree (Vitex agnus-castus), also known as chasteberry, has a long history of traditional use for supporting women’s reproductive health, including breast-related concerns. In traditional European herbal medicine, chaste tree was commonly used to address menstrual irregularities, premenstrual syndrome (PMS), breast tenderness (mastalgia), and symptoms associated with hormonal imbalances. The traditional rationale is that chaste tree acts on the pituitary gland to help balance levels of prolactin and other hormones, which may influence breast symptoms linked to the menstrual cycle.

Modern clinical studies have provided some support for chaste tree’s effect on cyclical mastalgia (breast pain associated with the menstrual cycle). A number of randomized controlled trials and systematic reviews suggest that extracts of Vitex agnus-castus can reduce breast pain and tenderness in women with PMS or premenstrual mastalgia, likely via dopaminergic effects that reduce prolactin secretion. However, while these findings are promising, the quality and size of studies vary, and further research is needed for more definitive conclusions. There is little evidence directly supporting chaste tree for other breast health concerns outside the context of cyclical pain or PMS.

In summary, the use of chaste tree to support the breasts is primarily grounded in traditional use, with moderate scientific evidence for its effectiveness in reducing cyclical breast tenderness associated with PMS.