Agnus castus goes by many names, including chaste tree berry, monk’s pepper and vitex. It has been used for thousands of years as an herbal remedy for female problems and as a libido suppressant for males. Homer mentions the plant as a symbol of chastity in "The Iliad," and monks traditionally chew on the berries to aid in their vow of celibacy.
Although it is an all-natural herbal treatment, vitex can have powerful side effects. Agnus castus is a potent plant-based source of sex hormones and can effectively raise progesterone levels in women and lower testosterone levels in men.
Agnus castus can reduce menopausal symptoms, especially hot flashes. It can help moderate heavy periods and lengthen short cycles and will clear up acne in both men and women. Doctors use chaste tree berry to treat endometriosis and to increase female fertility. Agnus castus also has an analgesic effect, relieving pain from muscle cramps and headache.
Male Side Effects
Agnus castus suppresses the male sex hormones and is a known anaphrodisiac, reducing sexual desire. Agnus castus prevents sperm production and can affect the testes, causing temporary or permanent male infertility. Animal studies have shown that agnus castus can atrophy the testicles.
The National Institute of Health has found that agnus castus can treat prostate cancer, and the herb also treats prostatitis, an inflammation of the prostate gland.
Female Side Effects
Agnus castus can cause longer and heavier periods. It also can increase fertility, including causing the ovaries to release more than one egg. This effect can cause twins or other multiple births. Agnus castus can affect hormonal medications, including birth control pills and estrogen replacement therapy.
Agnus castus is often used in an attempt to increase milk supply, but it actually reduces prolactin, the breastfeeding hormone needed for milk production. It may be excreted in breastmilk and could have a hormonal effect on babies who drink affected milk.
Other Side Effects
Agnus castus can interfere with certain medications, including L-dopa, used to treat Parkinson’s disease; haloperidol (Haldol); and Zyban. Because agnus castus is taken internally, it can cause stomach upset. Skin problems such as crawling or itching sensations have also been reported by women and it may cause skin rashes. Some people may have an allergic reaction to agnus castus.
Pregnant and nursing mothers should not use agnus castus. Women with hormone-sensitive cancers, including breast cancer and cervical cancer, should avoid the herb. Women with iron deficiencies (anemia) and men trying to become fathers should also avoid agnus castus.