Vitex (Chasteberry)

📜 Historical Use

The common names record the plant’s original purpose rather than its modern one. NCCIH lists chaste tree, gattilier, monk’s pepper and vitex alongside chasteberry, and reports that medieval monks are said to have used the berries to reduce sexual desire - the origin of both the chastity reference and the peppercorn nickname. Beyond that, NCCIH records traditional use for psychological complaints, gynaecological disorders and hormone-related skin conditions. The modern supplement market, NCCIH notes, has moved the plant almost exactly opposite: it is now sold chiefly for premenstrual syndrome, breast pain, infertility and menopausal symptoms, so a herb once taken to suppress libido and fertility is now taken to support conception, and MSK notes one study in which sexual function improved. That reversal is worth stating because it is often presented on supplement pages as an unbroken tradition of use for women’s hormonal health, which the historical record does not show. NCCIH also notes the regulatory position: dietary supplements containing chasteberry are not approved by the FDA before they are sold, and responsibility for safety and accurate labelling rests with the manufacturer.

📊 What the Research Shows

NCCIH characterises the research on chasteberry as low-to-moderate quality overall, and that qualification applies to every use below. On premenstrual syndrome and cyclical breast pain - the uses the supplement is actually sold for - NCCIH says research suggests chasteberry might reduce symptoms such as breast tenderness, but states plainly that higher-quality evidence is needed to reach any definitive conclusions. MSK agrees that clinical studies suggest it can reduce PMS symptoms and that several randomised placebo-controlled trials have been run, while noting that a systematic review highlighted the need for well-designed studies before definitive conclusions can be drawn. No source read here supports a specific percentage figure for PMS improvement. On heavy menstrual bleeding, NCCIH cites a single low-quality study of IUD-related bleeding and calls the evidence insufficient. On infertility and sexual dysfunction, NCCIH says there is not enough reliable evidence, with one study suggesting possible improvement in sexual function. On menopausal symptoms the picture is worse than merely unproven: NCCIH describes one preliminary study needing further investigation, and MSK reports that chasteberry combined with St John’s wort was ineffective for menopausal symptoms. Reported antifungal effects come from initial laboratory reports with no human studies behind them. MSK limits its dysmenorrhoea support to women aged twenty to forty whose ovarian function was not greatly impaired and who had no other hormone imbalances.

Take 20-40mg standardized extract daily in the morning on empty stomach. Allow 3 full cycles for results.

Avoid with hormonal contraceptives, IVF, or hormone-sensitive cancers. Takes 3 months to work.

⚠️ What happens if taken in excess:

Excessive doses may disrupt hormonal balance rather than restore it, causing irregular periods, acne, and breast tenderness. Can interfere with IVF treatments and hormonal contraceptives. Very high doses may cause rashes, headaches, and GI upset. Not safe during pregnancy.

Chasteberry has named, specific interaction concerns, and the single most practically important one is contraceptive failure. MSK reports that preclinical studies suggest chasteberry may decrease the effects of hormone therapies, including reducing the effectiveness of oral contraceptives - which matters disproportionately because the people most likely to take chasteberry for PMS are the people most likely to be on them. MSK also flags antipsychotic phenothiazines by name, listing chlorpromazine, haloperidol and prochlorperazine, with preclinical studies suggesting chasteberry may interfere with the action of these drugs or enhance their side effects; the same concern is raised for antiparkinson dopamine agonists, whose effectiveness it may interfere with. Both follow from the dopaminergic activity described in the mechanism section. On metabolism, MSK states that in vitro chasteberry inhibits CYP2C19 and CYP3A4 and may therefore affect drugs metabolised by those two enzymes, which between them handle a large share of prescription medicines. The qualification MSK attaches to every one of these is important and should not be dropped: clinical relevance has yet to be determined, meaning these are laboratory and animal findings rather than documented human case reports. NCCIH does not detail specific interactions for chasteberry, saying only that herbal products should be discussed with a health care provider because some herbs and medicines interact in harmful ways.

1. Chasteberry: Usefulness and Safety — National Center for Complementary and Integrative Health NIH NCCIH (2025)[NIH ↗]
2. Chasteberry — Memorial Sloan Kettering Cancer Center, Integrative Medicine - About Herbs MSKCC About Herbs (2021)[mskcc ↗]