Vitex agnus castus, also called chasteberry, is one of the most popular botanicals in Europe for treating menstrual disorders and has been recognized as gentle and effective for 2,500 years. Numerous clinical studies document its benefit.
Many menstrual problems can be traced to deficient progesterone production during the second half of the menstrual cycle, also called the luteal phase. Insufficient progesterone during this phase of the menstrual cycle results in estrogen dominance, leading to a shortening of that part of the cycle, commonly referred to as luteal phase defect. A shortened luteal phase with too much estrogen and not enough progesterone causes all kinds of problems for women: heavy periods, scanty periods, too frequent periods, or no periods at all. Another pituitary hormone, prolactin, may also be elevated during this time, resulting in breast tenderness and pain, a classic symptom of PMS.
How does vitex help?
First of all, what does it not do? Vitex does not act as a phytoestrogen (plant estrogen), a term commonly associated with balancing the female reproductive system. Vitex works through another important chemical pathway, the hypothalamus-pituitary axis, to balance female hormones. Vitex increases luteinizing hormone production while inhibiting the release of follicle stimulating hormone, leading to an indirect increase in progesterone and a normalization of prolactin levels. The combination of actions produced by vitex seems to restore the estrogen/progesterone balance.
Vitex and PMS
Clinical studies using vitex extract show a reduction in headaches, breast tenderness, bloating, fatigue, cravings for sweets, and also feelings of anxiety, irritability, depression and mood swings, after only one month. Vitex tincture, at an average daily dose of 42 drops, was prescribed for 2447 women who had a variety of menstrual disorders, including PMS. Although this was an uncontrolled study, both patients and physicians reported that vitex significantly improved symptoms. At the end of the study 31% of patients had complete relief of symptoms, and 55% reported significant improvement. “The doctors and patients were satisfied with the treatment in over 90% of cases, i.e., symptoms either disappeared altogether or were significantly improved. The good acceptability of the preparation is also shown by the long duration of the treatment, with a mean of 5 months, and up to 9 years in some cases...The tolerance is exceptional: only 2.3% of patients experienced unwanted effects with the treatment...” 
In another uncontrolled observational study 1,542 women were given 42 drops of vitex tincture (Agnolyt) each day. Among the patients, 33% had complete relief of symptoms while 57% reported improvement. Again, their doctors rated vitex tincture as very good, good, or satisfactory in 93% of the cases. 
Women with PMS may want to use vitex either alone or preferably as part of a comprehensive herbal formula. Clinical studies using vitex show a reduction in headaches, breast tenderness, bloating, fatigue, cravings for sweets, and also feelings of anxiety, irritability, depression and mood swings, often after only one month.
Low levels of progesterone are believed to contribute significantly to menopausal symptoms. The ability of vitex to increase the secretion of luteinizing hormone which raises progesterone levels is the likely mode of action. Physicians in Europe commonly recommend vitex for the treatment of hot flashes.
Vitex is used as a way to prevent repeat uterine fibroids, and is probably the most effective herb in the treatment of menorrhagia. However, it needs to be used for several months before its effects are noticed.
Vitex is often used to help infertility caused by a luteal phase defect (a shortening of the post-ovulatory part of the menstrual cycle): women taking vitex for three months appear to have more success at becoming pregnant. 
The herb vitex can help the body establish a proper balance between estrogen and progesterone by encouraging the production of progesterone.  If taken regularly for several months, it helps to restore hormonal balance and alleviate PMS symptoms. 
In one study of 100 nursing mothers, vitex was shown to significantly improve milk flow and milk-release when compared to placebo.  Vitex is traditionally taken the first day after birth and continued for ten days. Vitex is only recommended if there are any problems with milk production.
Herbalists have used vitex with much success in treating teenage acne. Well-known herbalist and author, Christopher Hobbs, finds vitex very useful for treating teenage acne, preferably accompanied by changes in eating habits. “I have worked with some teenagers who had chronic acne for several years who were not willing to change their diet in any way. They felt attached to soft drinks, french fries, pizza and hamburgers, and no amount of logical discussion could change their minds. If vitex can help in these cases, it seems likely to help in other cases where dietary improvements are possible, and in my experience it can help dramatically. I have given it to both young men and women with equal effectiveness. The remedy often takes from one to two months before it becomes fully active.” 
Dosage and safety
Recommended Dosage: Different forms and concentrations make general dosage recommendations difficult. It is recommended that you follow the label instructions or your doctor's advise. 40 drops (2ml) of vitex extract or 120 drops (6ml) tincture taken daily can be used for up to eighteen months continuously, unless pregnancy occurs (at which point vitex use should be discontinued). Two tablets (250mg each) of an dry extract is also a common recommendation.
The safety of vitex is exceptional - in one study, vitex was given up to 9 years in some cases, with very few side-effects. It is usually recommended by that Vitex be taken as a single daily dose first thing in the morning. It may interfere with the effectiveness of birth control medications. It is important to note that Vitex is not a fast acting medication and needs to be taken consistently for some time. The average length of treatment is six months.
- Loch, E. Bohnert K.J. Peeters M, et al. “The treatment of menstrual disorders with Vitex agnus-castus tincture.” Der Frauenarzt. 1991. 32(8): pp.867-70.
- Dittmar, F., Bohnert, K.J., Peeters M. et al. “Premenstrual syndrome: treatment with a phytopharmaceutical.” Therapiewoche Gynakol. 1992. 5(1): pp.60-8.
- Lauritzen, C.H. et al. “Treatment of premenstrual tension syndrome with Vitex agnus castus: controlled, double-blind study versus pyridoxine.” Phytomed. 1997. 4: pp.183-9.
- Mohr, H. “Clinical investigations of means to increase lactation.” Dtsche. Med. Wschr. 1954. 79 (41): pp.1513-1516.
- Hobbs, Christopher. Vitex: the women’s herb. 2nd ed. 1996. Botanica Press.