Chasteberry is frequently called by its Latin names: vitex or, alternatively, agnus-castus. A shrub in the verbena family, chasteberry is commonly found on riverbanks and nearby foothills in central Asia and around the Mediterranean Sea. After its violet flowers have bloomed, a dark brown, peppercorn-size fruit with a pleasant odor reminiscent of peppermint develops. This fruit is used medicinally.

As the name implies, for centuries chasteberry was thought to counter sexual desire. A drink prepared from the plant's seeds was used by the Romans to diminish libido, and in ancient Greece, young women celebrating the festival of Demeter wore chasteberry blossoms to show that they were remaining chaste in honor of the goddess. Monks in the Middle Ages used the fruit for similar purposes, yielding the common name "monk's pepper."

What Is Chasteberry Used for Today?

The modern use of chasteberry dates back to the 1950s, when the German pharmaceutical firm Madaus Company first produced a standardized extract. This herb has become a standard European treatment for cyclic breast tenderness, a condition related to PMS that is sometimes called cyclic mastitis, cyclic mastalgia, mastodynia, or fibrocystic breast disease. Chasteberry also appears to be useful for general PMS symptoms.

Chasteberry is believed to work by suppressing the release of prolactin from the pituitary gland.1-4 Prolactin is a hormone that naturally rises during pregnancy to stimulate milk production. Inappropriately increased production of prolactin may be a factor in cyclic breast tenderness, as well as other symptoms of PMS.

Elevated prolactin levels can also cause a woman's period to become irregular and even stop. For this reason, chasteberry is sometimes tried when menstruation is irregular, or stops altogether (amenorrhea). Note: We recommend that you do not attempt to self-treat significant menstrual irregularities without a full medical evaluation. There could be a serious medical condition causing the problem that you wouldn't want to miss.

High prolactin levels can also cause infertility in women. For this reason, chasteberry is sometimes tried as a fertility drug;5 however, the two double-blind studies performed to evaluate this possible use failed to return statistically significant results.6,7

Chasteberry is sometimes used for menopausal symptoms, but there is as yet no evidence that it is effective, either alone or in combination with other herbs.19

A review of 13 randomized trials evaluated chasteberry for managing PMS and premenstrual dysphoric disorder (a more severe form of PMS associated with psychiatric symptoms). Chasteberry was associated with reduced PMS symptoms including breast pain, and regulation of the menstrual cycle when compared to placebo, vitamin B, or magnesium oxide. However, there was no clear benefit for premenstrual dysphoric disorder symptoms when compared to an antidepressants.24

What Is the Scientific Evidence for Chasteberry?

There is a growing body of scientific research supporting the use of chasteberry.

Cyclic Mastalgia

A double-blind, placebo-controlled trial of 97 women with symptoms of cyclic mastalgia found that treatment with chasteberry extract significantly reduced pain intensity by the end of one menstrual cycle.8 The reduction continued to increase throughout the second menstrual cycle, and at the end of both the first and second cycle, women in the treated group were doing better than those receiving placebo.

However, something interesting happened in the third cycle. The benefits of chasteberry treatment reached a plateau, while the placebo group continued to improve. At the end of the third cycle, those receiving chasteberry were still doing better, but the difference was no longer statistically significant.

Another double-blind trial of 104 women compared placebo against two forms of chasteberry (liquid and tablet) for at least three menstrual cycles.9 The results showed statistically significant and comparable improvements in the treated groups as compared to placebo.

Benefits were also seen in a double-blind trial that enrolled 160 women with cyclic breast pain. The women were given either chasteberry, a drug related to progesterone, or placebo, and were followed for at least four menstrual cycles.10 Although there were many dropouts, the results again suggest that chasteberry is superior to placebo.

Premenstrual Syndrome (PMS)

Chasteberry has consistently shown promise in relieving symptoms in women with PMS. A double-blind, placebo-controlled study of 178 women found that treatment with chasteberry over three menstrual cycles significantly reduced general PMS symptoms.11 The dose used was 1 tablet 3 times daily of a dry chasteberry extract. Women in the treatment group experienced significant improvements in symptoms, including irritability, depression, headache, and breast tenderness. In a similar study, 217 women with moderate to severe PMS were randomized to receive chasteberry extract or placebo.21 After three menstrual cycles, the women in the treatment group reported fewer symptoms. A smaller trial involving 67 women also reported on the effectiveness of chasteberry for PMS.22

A double-blind randomized trial of 162 women with PMS compared 8, 20, and 30 mg doses of chasteberry and placebo over the course of three menstrual cycles. Women who took 20mg or 30mg of chasteberry had significantly greater reduction in symptom scores compared to placebo with the greatest reduction in 20 mg dose. There was no significant difference when comparing 8mg to placebo.23

Chasteberry in combination with St. John's wort was also studied for PMS symptoms during late menopause with favorable results in at least one small trial.20

There is also some conflicting evidence, though. A double-blind trial compared chasteberry to vitamin B6 (pyridoxine) instead of a placebo.12 The two treatments proved equally effective. However, because vitamin B 6 itself has not been shown effective for PMS, these results mean little.13

Two other studies are often cited in support of chasteberry as a treatment for PMS. These were rather informal reports of a total of about 3,000 women with PMS given chasteberry by their physicians.14,15 The physicians rated chasteberry as effective about 90% of the time, but in the absence of a control group, these reports are not very meaningful.

Irregular Menstruation

One double-blind trial followed 52 women with a form of irregular menstruation known as luteal phase defect.16 This condition is believed to be related to excessive prolactin release. After 3 months, the women who took chasteberry showed significant improvements.

Dosage

The typical dose of dry chasteberry extract is 20 mg taken 1 to 3 times daily. Chasteberry is also sold as a liquid extract to be taken at a dosage of 40 drops each morning. However, extracts that require lower or higher dosing are also available. We recommend following the label instructions.

Safety Issues

There haven't been any detailed studies of the safety of chasteberry. However, its widespread use in Germany has not led to any reports of significant adverse effects,17 other than a single case of excessive ovarian stimulation possibly caused by chasteberry.18

Because it lowers prolactin levels, chasteberry is not an appropriate treatment for pregnant or nursing women. Safety in young children or those with severe liver or kidney disease has not been established.

There are no known drug interactions associated with chasteberry. However, it is quite conceivable that the herb could interfere with hormones or medications that affect the pituitary gland.

Interactions You Should Know About

If you are taking hormones or drugs that affect the pituitary, such as bromocriptine, it is possible that chasteberry might interfere with their action.