At a glance: Agnus castus, or chasteberry, is the fruit of Vitex agnus-castus L. and is chiefly studied for premenstrual syndrome (PMS) and cyclic breast pain. Several trials report benefit, but the evidence becomes much less impressive when study quality and herbal-product characterisation are examined closely. One 2017 meta-analysis found a large pooled effect but also very high heterogeneity, high risk of bias and publication bias; a 2019 meta-analysis restricted to properly characterised products found only three eligible placebo-controlled trials. Agnus castus is therefore a good example of why the quality of an herbal intervention description matters as much as the p-value.[1][2][3]
Botanical profile
- Accepted name: Vitex agnus-castus L.
- Common names: agnus castus, chasteberry, chaste tree, monk’s pepper.
- Family: Lamiaceae. Older literature may place the genus in Verbenaceae.
- Medicinal part: fruit.
- EMA herbal drug name: Agni casti fructus.[1]
Vitex agnus-castus is a Mediterranean and Central Asian shrub or small tree with palmate leaves and violet-blue flower spikes. The medicinal fruit is a small dark drupe-like fruit sometimes described commercially as a berry.
Major constituent groups
Agnus-castus fruit contains several chemically distinct groups, including:
- iridoid glycosides, including agnuside and aucubin;
- diterpenes, some of which have been investigated for dopaminergic activity;
- flavonoids, including casticin and related compounds;
- volatile-oil constituents; and
- other phenolic and lipid-soluble compounds.
Different proprietary extracts can vary in extraction solvent and chemical profile. That is one reason trials using named preparations such as Ze 440 or BNO 1095 should not be treated as proof for every supplement sold as “Vitex”.
Traditional use
Agnus castus fruit has a long European and Mediterranean tradition in menstrual and reproductive complaints, including irregular cycles, premenstrual symptoms and cyclic breast tenderness. Its older reputation as “chaste tree” or “monk’s pepper” comes from historical use intended to reduce sexual desire in monastic settings. In later Western herbal practice it became particularly associated with cyclical menstrual symptoms and reproductive endocrine complaints.
Contemporary herbal practice
Agnus castus is used in contemporary Western herbal practice chiefly for cyclical reproductive complaints: premenstrual symptoms, cyclic breast tenderness and certain patterns of menstrual irregularity. It is often prescribed as a single daily preparation rather than as a flavour component in a mixed tea. Practitioners tend to assess the menstrual pattern across several cycles because the herb is usually used as a longer-term endocrine-directed medicine rather than an immediate symptomatic remedy.
EMA regulatory assessment
The European Medicines Agency HMPC has an EU herbal monograph for agnus-castus fruit. Revision 1 was published in October 2018. A later call for scientific data for Revision 2 closed in May 2024, and the EMA page currently lists the monograph as undergoing periodic scientific review.[1]
This is useful for students because it shows that a regulatory monograph is not a frozen historical document; the evidence base is periodically revisited.
PMS: what does the evidence say?
A 2017 systematic review identified 17 randomised controlled trials and included 14 in quantitative analysis. Most trials reported positive effects. However, the pooled placebo-controlled effect was accompanied by very high heterogeneity (I² 91%), substantial risk of bias and evidence of publication bias. The authors concluded that the pooled benefit was exploratory and probably overestimated the true effect.[2]
A 2019 meta-analysis deliberately applied stricter criteria based on proper characterisation of herbal products. Of 21 clinical trials found, only three double-blind placebo-controlled trials involving 520 participants met those criteria. In those studies, the characterised extracts Ze 440 and BNO 1095 were associated with a higher likelihood of symptom response than placebo, but the authors again called for better-characterised trials.[3]
That is an unusually clear methodological lesson: when the intervention is a complex botanical extract, a trial cannot be interpreted properly if the preparation itself is poorly described.
Cyclic breast pain
A 2020 systematic review and meta-analysis assessed agnus castus for cyclic mastalgia. It reported improvement in breast-pain intensity across a mixed evidence base and found a moderate pooled effect in a conservative analysis of six placebo-controlled studies. However, risk of bias was unclear in many studies and the authors still called for better trials.[4]
Cyclic mastalgia may occur as part of PMS, but persistent, focal, new or otherwise concerning breast symptoms should not be reduced to a hormonal self-treatment problem without appropriate assessment.
“Hormone balancing” is not a scientific mechanism
Agnus castus is routinely marketed as a “hormone-balancing” herb. That phrase is too vague to be useful scientifically. Hormones are different molecules controlled by different organs, feedback loops and receptors; they cannot sensibly be described as one substance that is either “balanced” or “unbalanced”.
Experimental research has particularly investigated dopaminergic effects of some diterpenes and possible downstream effects on prolactin secretion. This provides a mechanistic hypothesis for some menstrual and breast symptoms, but it does not justify a blanket claim that agnus castus normalises the endocrine system.
Preparations
Clinical studies have used dry extracts and other characterised preparations of the fruit. Extraction solvent, drug-to-extract ratio and marker compounds should be recorded where reported. A tea, tincture, powdered fruit capsule and proprietary dry extract are not necessarily interchangeable.
Safety
NCCIH reports that agnus-castus fruit extract is generally well tolerated in short-term research, with mild adverse effects such as nausea, abdominal discomfort, diarrhoea, headache and itching reported in some users.[5]
Short-term tolerability does not establish long-term safety, and self-treatment should not delay investigation of persistent menstrual irregularity, infertility, unexplained bleeding or new breast symptoms.
Hormone-sensitive conditions
NCCIH advises that chasteberry may not be safe in people with hormone-sensitive conditions such as breast, uterine or ovarian cancer.[5]
That caution should not be translated into a claim that agnus castus simply acts as oestrogen. Rather, the endocrine and reproductive context makes unsupervised use inappropriate where hormone-sensitive disease is relevant.
Pregnancy and breastfeeding
NCCIH states that use during pregnancy or breastfeeding may be unsafe.[5] Products promoted for fertility are particularly liable to create a contradiction here: a person using agnus castus while trying to conceive needs to know what to do if pregnancy occurs rather than assuming that a “fertility herb” remains suitable throughout pregnancy.
Possible medicine interactions
Because dopaminergic and endocrine mechanisms have been proposed, theoretical interaction concerns include dopamine agonists or antagonists and hormonal medicines. The clinical importance of every proposed interaction is not equally established, so medication review is preferable to a generic list of absolute prohibitions.
Student note: common evidence traps
- “Hormone balancing” is a marketing phrase, not a defined pharmacological endpoint.
- A large pooled effect can still come from a biased, heterogeneous evidence base.
- Record the proprietary extract and extraction details where possible.
- Do not combine PMS, PMDD, cyclic mastalgia, infertility and menopause as though they are one indication.
- A positive trial of Ze 440 or BNO 1095 is not automatic evidence for an uncharacterised Vitex supplement.
- Check whether diagnostic criteria for PMS or PMDD were prospectively defined.
- Publication bias matters: a literature dominated by positive small studies can exaggerate the apparent effect.
References
- European Medicines Agency, Committee on Herbal Medicinal Products. Agni casti fructus — Vitex agnus-castus L., fructus. EU herbal monograph and assessment report. EMA. Revision 1 published 10 October 2018; Revision 2 scientific-data consultation closed May 2024.
- Verkaik S, Kamperman AM, van Westrhenen R, Schulte PFJ. The treatment of premenstrual syndrome with preparations of Vitex agnus castus: a systematic review and meta-analysis. American Journal of Obstetrics and Gynecology. 2017;217(2):150–166. doi:10.1016/j.ajog.2017.02.028. PubMed.
- Csupor D, Lantos T, Hegyi P, et al. Vitex agnus-castus in premenstrual syndrome: a meta-analysis of double-blind randomised controlled trials. Complementary Therapies in Medicine. 2019;47:102190. doi:10.1016/j.ctim.2019.08.024. PubMed.
- Ooi SL, Watts S, McClean R, Pak SC. Vitex agnus-castus for the treatment of cyclic mastalgia: a systematic review and meta-analysis. Journal of Women’s Health. 2020;29(2):262–278. doi:10.1089/jwh.2019.7770. PubMed.
- National Center for Complementary and Integrative Health. Chasteberry: Usefulness and Safety. NCCIH. Consulted September 2026.
- van Die MD, Burger HG, Teede HJ, Bone KM. Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials. Planta Medica. 2013;79(7):562–575. doi:10.1055/s-0032-1327831. PubMed.
Additional materia medica sources
- Blumenthal M, et al., eds. The Complete German Commission E Monographs. American Botanical Council; 1998.
- Mills S, Bone K. Principles and Practice of Phytotherapy. 2nd ed. Elsevier; 2013.
- Hoffmann D. Medical Herbalism. Healing Arts Press; 2003.
- British Herbal Medicine Association. Traditional-use and pharmacopoeial publications.
Last reviewed: 20 September 2026. Educational reference only; not an individual menstrual, fertility or prescribing guide.
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