Chasteberry (Vitex agnus-castus)

What it is

Vitex agnus-castus grows as a shrub in the Mediterranean region and in Central Asia. The ripe, dried fruits, which resemble peppercorns, are used. They are mostly made into alcoholic dry extracts. Commission E assessed chasteberry positively for cycle irregularities, premenstrual complaints and breast tenderness; since 2018 there has been a revised EU monograph from the European Medicines Agency.

The extract matters. Most of the good studies were run with two special extracts, Ze 440 and BNO 1095. The EU monograph recognizes a dry extract at 20 mg per day as well-established medicinal use in premenstrual syndrome; other preparations count as traditional medicines with at least 30 years of documented use. Results from one extract cannot simply be transferred to another product.

How it is supposed to work

The common explanation runs via dopamine and prolactin. Constituents from the group of diterpenes are supposed to dock onto dopamine D2 receptors in the pituitary gland and thus slow the release of prolactin. Slightly elevated prolactin is associated with breast tenderness, a shortened second half of the cycle and too little progesterone. In a cell model with the human D2 receptor, several diterpenes and, surprisingly, also triterpenes activated the receptor, the strongest in the low micromolar range.

In humans, this chain has only partly been shown. In a small study of women with latently elevated prolactin, prolactin release fell after three months, the second half of the cycle normalized and the progesterone deficiency disappeared, only under chasteberry. The EMA nevertheless writes that the mechanism of action is not known and that a lowering of elevated prolactin levels in humans has not been conclusively demonstrated.

What women who use it are looking for

Most women turn to chasteberry when the days before menstruation are a noticeable burden: irritable, low, bloated, with tender breasts. Many report that things calm down after two to three cycles, exactly the period over which the studies ran. Others use it for an irregular cycle, when trying to conceive with a short second half of the cycle, or during menopause. These are experience reports, and in premenstrual syndrome in particular the placebo effect is large; in a Chinese study it was 50 percent. If you try it, you therefore need some patience and an honest look at your own symptoms.

What the studies show

The 2001 BMJ study

170 women with PMS, on average 36 years old, took one tablet of Ze 440 or placebo daily for three cycles. The women themselves rated irritability, mood swings, anger, headaches, breast tenderness and bloating. The main endpoint improved considerably more under chasteberry. Symptoms halved in 52 percent under chasteberry and in 24 percent under placebo. Mild side effects occurred in 4 women on the active preparation and 3 on placebo.

The Chinese multicenter study

After a run-in phase, 217 women with moderate to severe PMS were assigned to BNO 1095, corresponding to 40 mg of herbal substance, or placebo and treated for up to three cycles. The diary score fell from 29.23 to 6.41 under chasteberry, and from 28.14 to 12.64 under placebo. The difference was clear, but the placebo effect, at 50 percent, was also large. No serious side effects occurred.

The dose-finding study

162 women between 18 and 45 years of age received placebo or 8, 20 or 30 mg of Ze 440 over three cycles. The 20 mg dose was clearly superior to placebo and to 8 mg; 30 mg brought no further benefit over 20 mg. All doses were well tolerated.

Where the data stop

The broad meta-analysis of 14 studies did find a large effect, but extremely high inconsistency of results and indications that negative studies were published less often. The authors therefore regard the effect sizes as exploratory and probably overestimated. Of 21 studies, only 3 met the requirements for a clearly described preparation in the strict analysis. Almost all the studies ran over three cycles; controlled long-term data are lacking.

Beyond PMS and breast pain, the evidence becomes thin. For elevated prolactin there are only small studies; the largest evaluated included 37 women. In the severe form PMDD, chasteberry was similarly effective to fluoxetine in a study with 41 women, but without a placebo group. For menopause there is one study with 52 women; a review notes that rigorous studies are lacking. And food supplements often contain powders or extracts that have never been tested in a study.

Status, approval and legal

Chasteberry has a dual status in Germany. Extracts are approved as herbal medicines and available without prescription in pharmacies, for example for cycle irregularities, premenstrual complaints and breast tenderness. The EU monograph recognizes one extract in PMS as well-established medicinal use. At the same time, the fruit may be used in food supplements; according to the BVL substance list, it is not considered a novel food there. The same list, however, lists chasteberry as a medicinal substance and recommends a restriction in foods; according to Commission E, 30 to 40 mg of herbal substance per day is considered pharmacologically active. Food supplements therefore must not have a pharmacological effect and must not be advertised for relieving complaints. There are no maximum levels from EFSA, BfR or DGE; chasteberry is not on the WADA 2026 prohibited list.

Safety

Chasteberry is considered well tolerated. Possible are nausea, abdominal pain, headache, dizziness, acne, itching, skin rash and cycle changes, rarely also severe allergic reactions with facial swelling and shortness of breath. Anyone who has or has had an estrogen-sensitive cancer, has had a disorder of the pituitary gland, or takes dopamine agonists, dopamine antagonists, estrogens or antiestrogens should speak to a physician beforehand. In a prolactin-producing tumor, chasteberry can mask symptoms. It is not recommended during pregnancy and breastfeeding; in an animal model, milk production decreased. It is not intended for adolescents under 18. Because the cycle can normalize, the chance of pregnancy also rises, according to the package leaflet of one preparation. New breast pain and cycle disorders should first be checked by a physician.

Sources

• Schellenberg, BMJ 2001 – chasteberry extract Ze 440 in premenstrual syndrome
• He et al., Maturitas 2009 – BNO 1095 in PMS, multicenter study in China
• Schellenberg et al., Phytomedicine 2012 – dose-dependent effect of Ze 440
• Csupor et al., Complement Ther Med 2019 – meta-analysis of double-blind RCTs
• Verkaik et al., Am J Obstet Gynecol 2017 – systematic review and meta-analysis PMS
• Ooi et al., J Womens Health 2020 – chasteberry in cyclical mastalgia
• Milewicz et al., Arzneimittelforschung 1993 – latent hyperprolactinemia and luteal phase defect
• Daniele et al., Drug Saf 2005 – systematic review of adverse events
• EMA/HMPC – EU herbal monograph Vitex agnus-castus L., fructus, Revision 1
• Verbraucherzentrale (German consumer advice center) – chasteberry capsules