Chaste Tree

Vitex agnus-castus

Family: Lamiaceae Part used: Berries (dried)

Key Compounds

• Agnuside
• Casticin
• Penduletin
• Orientin
• Isovitexin
• Apigenin
• Vitexin
• Luteolin
• Rotundifuran
• Bicyclogermacrene
• Sabinene
• Beta-farnesene

Traditional Use

• PMS (premenstrual syndrome) — the 2001 Schellenberg RCT (BMJ, 178 women, Agnucaston vs placebo over 3 months) showed significant reduction in total PMS score across five symptom categories: irritability, mood alteration, anger, headache, and breast fullness; response rate 52% vs 24% for placebo; this is among the best-designed clinical trials for a menstrual herb; German Commission E approved vitex for PMS, premenstrual mastalgia, and irregular menstrual cycles
• Prolactin reduction via dopamine pathway — vitex berry extracts bind dopamine D2 receptors in the anterior pituitary, reducing prolactin secretion; reduced prolactin → longer luteal phase → increased progesterone production; this is the established mechanism; it is neither phytoestrogenic nor directly progestogenic — it acts upstream on the hypothalamic-pituitary axis
• Premenstrual mastalgia (breast tenderness) — one of the best-supported specific applications; cyclic breast tenderness is closely related to elevated prolactin; the prolactin-reducing mechanism directly addresses the cause; several RCTs specifically for mastalgia have shown significant reduction in pain scores over 3-month treatment cycles
• Menstrual cycle regulation — German Commission E approved for irregularities of the menstrual cycle; clinical use for shortened luteal phase (luteal phase defect) and oligomenorrhoea; the dopaminergic prolactin reduction effectively lengthens the luteal phase, correcting the hormonal imbalance responsible for these conditions
• Fertility support — clinical use in luteal phase defect (insufficient progesterone production in second half of cycle); the prolactin-normalising effect corrects the hormonal environment for conception; a 1993 Milewicz et al. RCT showed significant improvement in luteal phase progesterone levels versus placebo; not a fertility drug but addresses a specific correctable hormonal pattern

The berries were used by medieval monks to suppress sexual desire. They called it monk’s pepper. The plant is now approved by the German Commission E for premenstrual syndrome.

Agnus-castus means chaste lamb. The monks used the berries during periods of religious observance. The pharmacological mechanism is dopamine receptor agonism, which reduces prolactin secretion from the pituitary gland. Whether this affects male libido is not established. What it does is normalise the hormonal environment of the second half of the menstrual cycle. The monks were using a female reproductive medicine for reasons that had nothing to do with women.

Greek physicians had known about the female applications since Hippocrates. The medieval reattribution took a few centuries to undo.

Meet the plant

A deciduous Mediterranean shrub growing to 2–5 metres. Compound leaves resembling cannabis. Spikes of violet-blue flowers. Small dark berries the size of peppercorns with a mild spicy taste — the source of the ‘monk’s pepper’ name.

What the mechanism actually is

Vitex does not contain phytoestrogens or progesterone. It does not directly stimulate progesterone production.

Casticin and other diterpene compounds in the berries bind dopamine D2 receptors in the anterior pituitary gland. Dopamine D2 receptor stimulation inhibits prolactin secretion. Reduced prolactin allows the luteal phase of the menstrual cycle to lengthen and normalise progesterone production.

The chain: vitex compounds → D2 receptor binding → reduced prolactin → longer luteal phase → more progesterone.

The result is indistinguishable from ‘progestogenic effect,’ which is why vitex was described as progestogenic for decades before the mechanism was established. It acts upstream of progesterone, through a hormonal regulatory pathway. This is a more elegant mechanism than direct hormone supplementation — it normalises the system rather than overriding it.

Some compounds in vitex also bind μ-opioid receptors, which may account for the mood, headache, and irritability components of the PMS response.

The 2001 BMJ trial

Schellenberg et al. enrolled 178 women with PMS in a randomised, double-blind trial comparing Agnucaston (standardised vitex extract) to placebo over three menstrual cycles.

Symptom domains assessed: irritability, mood alteration, anger, headache, and breast fullness. All five domains improved significantly in the vitex group. Responder rate: 52% for vitex versus 24% for placebo.

That 28 percentage-point difference is a clinically meaningful outcome. The trial was published in the BMJ, designed to current clinical trial standards, and became the primary evidence for the German Commission E approval.

Three cycles (months) is the minimum for assessment. The mechanism requires time — each cycle becomes progressively better regulated as prolactin normalises.

The historical distortion

Hippocrates and Dioscorides documented vitex for uterine conditions and post-partum use in the classical period. These were female reproductive applications, accurately observed.

The medieval monastic reframing — the chaste monks, the anaphrodisiac berries — attached the plant to a male celibacy narrative. The accurate female reproductive applications were not pursued through this period. When German pharmacological research in the 1940s–70s began investigating vitex for menstrual applications, they were in some sense rediscovering what had been known and then obscured.

The name that survived (chaste tree, monk’s pepper) reflects the medieval attribution, not the clinical utility.

What people actually do with it

Extract (standard preparation): Standardised extract (equivalent to approximately 30 mg dried berry) taken once daily in the morning. Products are often standardised to agnuside content (0.5% minimum) or to casticin. Once-daily dosing is preferred over split dosing.

Tincture: 2–4 mL once daily in the morning. Once-daily timing is not arbitrary — morning dosing aligns with the circadian rhythm of prolactin secretion.

Dried berry capsules: 250–500 mg daily.

Minimum trial period: 3 months. Most practitioners recommend 3–6 months for full assessment. If no effect at 6 months, an alternative approach should be considered — vitex works through a specific hormonal mechanism that may not be the relevant mechanism for all menstrual irregularities.

Caution: Avoid during pregnancy (uterotonic potential). Do not combine with hormonal contraceptives or HRT without medical guidance. The hormonal mechanism means interactions with drugs acting on the same axis are pharmacologically significant.

Could you grow this yourself?

Yes — V. agnus-castus is a garden shrub in warm temperate and Mediterranean climates. It requires full sun and well-drained soil, tolerates drought, and produces its purple flower spikes in summer. Hardy to approximately -10°C (15°F). In colder climates it may need wall protection.

The berries ripen in autumn. Commercial preparations use standardised extracts; home-dried berries provide less consistent agnuside or casticin content but are usable.

Chaste tree (チェストベリー) in Japan

Japanese traditional medicine has no relationship with vitex (agnus-castus). Japan has a native Vitex species — 人参木 (V. rotundifolia, beach vitex), used topically in Okinawan folk medicine — but this is different from the Mediterranean chaste berry.

チェストベリー and セイヨウニンジンボク are used in the Japanese supplement market for menstrual regulation and PMS. The German Commission E approval and the Schellenberg BMJ trial are cited in Japanese supplement marketing. Interest follows the Western herbal supplement pattern.

Things you’re probably wondering

Why is it called chaste tree if the monk story doesn’t hold up pharmacologically? The name survives because names survive. The monastic attribution is historically real even if the mechanism is not what the monks believed. The plant does have a legitimate application — it just was not the one the monks thought they were using it for.

Is it a hormone? No. It contains no hormones. It modulates the regulatory signals (prolactin via D2 receptor agonism) that control the cycle, rather than adding hormones directly. This is why it’s considered safer than direct hormonal therapy for long-term use.

Can men use it? The prolactin-reducing mechanism applies to men — elevated prolactin in men causes libido reduction and fertility issues. Vitex has been used to reduce elevated prolactin in men, though this is far less studied and less commonly recommended than the female applications.

Botanical details

The full compound list

See Also

• Red Clover — genuine phytoestrogenic mechanism; contrast with vitex’s dopaminergic prolactin regulation
• Black Cohosh — serotonergic mechanism for menopausal symptoms; different target and application
• Evening Primrose — GLA for PMS mastalgia (breast tenderness); complementary mechanism

References

• Schellenberg, R. (2001). Treatment for the premenstrual syndrome with agnus castus fruit extract: prospective, randomised, placebo controlled study. BMJ, 322(7279), 134–137.
• Milewicz, A. et al. (1993). Vitex agnus castus extract in the treatment of luteal phase defects due to latent hyperprolactinaemia. Arzneimittelforschung, 43(7), 752–756.
• Wuttke, W. et al. (2003). Chaste tree (Vitex agnus-castus) — pharmacology and clinical indications. Phytomedicine, 10(4), 348–357.
• He, Z. et al. (2009). Vitex agnus-castus for premenstrual syndrome and premenstrual dysphoric disorder: a systematic review. BJOG, 116(13), 1–9.