Chasteberry

What it is

Chasteberry is the fruit of the shrub Vitex agnus-castus, and fruit extracts have long been used for premenstrual and menstrual complaints [1]. Trials used standardised extracts such as Ze 440 and BNO 1095, as well as liquid drops; the exact product matters [2].

What the research says

A 2019 meta-analysis of three double-blind, placebo-controlled trials (520 women) found that women taking chasteberry were 2.57 times as likely to have their symptoms go into remission as those on placebo (95% CI 1.52 to 4.35) [3]. A 2017 meta-analysis of 14 trials found a large pooled effect (Hedges g −1.21), but heterogeneity was very high (I² 91%) and most trials had a high risk of bias, so the authors judged the figure likely overstated [4]. In a 2013 review, seven of eight PMS trials found the extract superior to placebo or to other treatments [5].

In a trial of 162 women, 20 mg a day of Ze 440 reduced symptoms more than placebo or 8 mg, and 30 mg was no better than 20 mg [6]. In a three-cycle trial of 67 women using BNO 1095, the symptom score fell from 29.4 to 4.3 and from 28.8 to 11.8 with placebo [7].

Doses used in studies

Ze 440 was tested at 8, 20 and 30 mg a day for three menstrual cycles; 20 mg was the dose that beat placebo [6]. BNO 1095 was given as one tablet a day for three cycles [7]. One drop-based extract was taken as 40 drops a day from six days before menses, over six cycles [8]. A Japanese open-label study used 20 mg a day for three cycles, with no control group [9].

Safety and interactions

The most frequent side effects in the reviewed data were nausea, headache, stomach upset, menstrual changes, acne, itching and rash; they were mild and reversible [1]. One Japanese open-label study reported no substantial adverse events [9]. No drug interactions were reported in the safety review, but it noted a theoretical risk with medicines that block dopamine [1]. Reviews advise avoiding chasteberry during pregnancy or breastfeeding, and human evidence on pregnancy is poor [1][10]. In rats, an extract given before or during pregnancy changed pregnancy and fetal outcomes; this is animal data only [11]. Our searches found no human studies on liver injury, kidney disease, bleeding disorders, or upper limits and toxic doses.

Caveats and open questions

Many trials were small, and the 2019 review found that most could not be used as efficacy evidence because the product was poorly described [3]. Only two trials compared chasteberry with fluoxetine for severe PMS, with mixed results [5]. A pilot trial of PREMEN-CALM, a combination product, found no difference between the active and placebo groups in 42 women [12]. A 2024 real-world study of 1,700 women had no placebo group, and several authors are employees of Bionorica SE [13]. No recruiting trials were found in the registry search.