Vitex agnus-castus is a popular herbal supplement used to treat a variety of health problems.

It’s most commonly used against premenstrual syndrome (PMS), menstrual disorders, infertility, acne, menopause and nursing difficulties.

It’s also touted as protection against insect bites and certain types of cancer and claimed to offer a variety of other health effects. However, not all benefits are backed by science.

Here are the science-backed benefits — as well as some myths — associated with Vitex agnus-castus.

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Vitex, which is the name of the largest genus in the Verbenaceae plant family, includes 250 species worldwide (1).

Vitex agnus-castus is the most common Vitex used medicinally.

The Vitex agnus-castus fruit, also known as chasteberry or monk’s pepper, is about the size of a peppercorn. It’s produced by the chaste tree, which acquired its name because its fruit was likely used to decrease men’s libido during the Middle Ages (2).

This fruit — as well as other parts of the plant — are typically used as an herbal remedy to treat a variety of ailments.

For instance, Vitex agnus-castus is used to treat PMS, symptoms of menopause, infertility issues and other conditions affecting a woman's reproductive system. In fact, it’s been used in this way since ancient Greece (2).

In Turkish medicine, it’s also used as a digestive, antifungal and anti-anxiety aid (3).

Summary Vitex agnus-castus is a plant frequently harvested as an herbal remedy for a variety of ailments. Its most popular use is to relieve PMS, menopause symptoms and infertility issues.

Vitex agnus-castus if particularly known for its ability to improve conditions affecting a woman’s reproductive system.

Eases Symptoms of Premenstrual Syndrome (PMS)

One of Vitex agnus-castus’ most popular and well-researched attributes is its ability to reduce symptoms of PMS.

These include constipation, irritability, depressed mood, migraines and breast pain and tenderness.

Researchers believe that Vitex works by decreasing levels of the hormone prolactin. This helps rebalance your other hormones, including estrogen and progesterone — thus reducing PMS symptoms (4).

In one study, women with PMS took either Vitex agnus-castus or a placebo for the days preceding three menstrual cycles. In total, 93% of those given Vitex reported a decrease in PMS symptoms including depression, anxiety and cravings (5).

In two smaller studies, women with PMS were given 20 mg of Vitex agnus-castus per day or a placebo for three menstrual cycles.

Twice as many women in the Vitex group reported a decrease in symptoms including irritability, mood swings, headaches and breast fullness, compared to those given the placebo (6, 7).

Vitex agnus-castus also appears to help reduce cyclic mastalgia, a type of breast pain linked to menstruation. Research suggests that it may be as effective as common drug treatment — but with far fewer side effects (8, 9, 10).

However, two recent reviews report that although Vitex appears helpful in reducing PMS symptoms, its benefits may be overestimated (11, 12, 13).

Better-designed studies may be needed before strong conclusions can be made.

May Reduce Menopause Symptoms

Vitex agnus-castus’ hormone-balancing effects may also help relieve symptoms of menopause.

In one study, Vitex oils were given to 23 menopausal women. Women reported improved menopause symptoms, including better mood and sleep. Some even regained their period (14).

In a follow-up study in which 52 additional pre- and postmenopausal women were given a Vitex cream, 33% experienced major improvements and another 36% reported moderate improvements in symptoms, including night sweats and hot flashes (14).

However, not all studies have observed benefits. One recent and larger double-blind, randomized, controlled trial — the gold standard in research — gave women a placebo or a daily tablet containing a combination of Vitex and St. John’s wort.

After 16 weeks, the Vitex supplement was no more effective than the placebo at reducing hot flashes, depression or any other menopausal symptoms (15).

Keep in mind that in many studies reporting benefits, women were provided with supplements that mixed Vitex agnus-castus with other herbs. Therefore, it’s difficult to isolate the effects of Vitex alone (16).

May Enhance Fertility

Vitex may improve female fertility due to its possible effect on prolactin levels (17).

This may be especially true in women with luteal phase defect, or a shortened second half of the menstrual cycle. This disorder is linked to abnormally high prolactin levels and makes it difficult for women to become pregnant.

In one study, 40 women with abnormally high prolactin levels were given either 40 mg of Vitex agnus-castus or a pharmaceutical drug. Vitex was as effective as the drug in reducing prolactin levels (18).

In another study in 52 women with luteal phase defect, 20 mg of Vitex resulted in lower prolactin levels and prolonged menstrual phases, while participants given a placebo saw no benefits (19).

Yet another study gave 93 women — who had unsuccessfully tried to become pregnant over the last 6–36 months — a supplement containing Vitex agnus-castus or a placebo.

After three months, women in the Vitex group experienced an improved hormone balance — and 26% of them became pregnant. In comparison, only 10% of those in the placebo group became pregnant (20).

Keep in mind that the supplement held a mix of other ingredients, making it difficult to isolate the effects of Vitex.

Irregular periods can also hamper women in planning a pregnancy. Three additional studies report that Vitex is more effective than a placebo in improving menstrual cycles in women with irregular periods (21, 22, 23).

Summary Vitex agnus-castus may reduce symptoms of PMS and menopause, though study results are mixed. By potentially decreasing prolactin hormone levels and stabilizing menstrual periods, it may also enhance fertility.

Vitex may also help keep a variety of insects at bay.

In one study, an extract made from Vitex seeds helped repel mosquitoes, flies, ticks and fleas for about six hours (24).

Another study revealed that a spray containing Vitex and other plant extracts protected against head lice for at least seven hours (25).

Research further shows that Vitex may kill lice larva and impede adult lice reproduction (25, 26).

Summary Vitex agnus-castus may offer some protection against insects, particularly mosquitoes, flies, ticks, fleas and head lice.

Compounds found in Vitex agnus-castus may combat certain types of cancer.

Test-tube studies demonstrate that Vitex extract helped kill cancerous colon, stomach, uterus, ovary, breast, cervix and lung cells (9).

Researchers believe that the plant’s antioxidant content may play a role.

However, human studies on the cancer-fighting properties of Vitex are needed before conclusions can be drawn (27).

Summary The antioxidants found in the Vitex agnus-castus fruit may help reduce the growth and spread of various types of cancer cells. However, more research is needed.

Vitex may also offer a range of additional benefits, including:

  • Reduced headaches: In one study, women prone to migraines given Vitex daily for three months reduced the number of headaches they experienced during their menstrual cycles by 66% (28).
  • Antibacterial and antifungal effects: Test-tube studies show that essential oils made from Vitex may fight harmful fungi and bacteria, including Staphylococcus and Salmonella bacteria (29, 30).
  • Reduced inflammation: Test-tube and animal studies suggest that compounds in Vitex may have anti-inflammatory properties. However, their effects aren’t stronger than those of aspirin (31, 32).
  • Cavity prevention: Test-tube studies point out that Vitex leaf oil may combat Streptococcus mutans, the main bacteria involved in dental cavities (33, 34).
  • Bone repair: In one study, women with bone fractures given a combination of Vitex and magnesium had slightly increased markers for bone repair than those given a placebo (35).
  • Stroke and epilepsy prevention: Animal studies note that Vitex may reduce the likelihood of stroke and epileptic seizures (36, 37).

That said, research supporting these benefits is limited. More studies are needed before strong conclusions can be drawn.

Summary Vitex may offer multiple other benefits, from headache reduction to improved dental health. However, more research is needed.

Vitex has been traditionally used to treat a wide variety of ailments. However, many of its uses are currently unsupported by scientific evidence.

The most popular unsubstantiated uses include:

  • Breastfeeding: While an old study postulated that Vitex may boost milk supply in nursing women, overall evidence isn’t strong — in fact, new research shows that Vitex may be unsafe to use while nursing (38).
  • Pain reduction: Though research links Vitex to numbed pain receptors in rats, no human studies have been done (39).
  • Treating endometriosis: Vitex may normalize hormonal imbalances, which could theoretically reduce symptoms of endometriosis, a female gynecologic disorder. However, no studies confirm this.
  • Baldness prevention: Vitex’ hormone-balancing effects are sometimes claimed to boost hair growth in men. However, no research can be found to support this.
  • Acne treatment: Three studies assert that Vitex may reduce acne faster than conventional treatments. However, these studies are decades old and newer research hasn’t confirmed these effects (40).
Summary While Vitex agnus-castus is used as an alternative remedy to treat various symptoms, many purported benefits are not backed by research.

Vitex agnus-castus is typically considered safe.

Researchers report that 30–40 mg of dried fruit extracts, 3–6 grams of dried herb or 1 gram of dried fruit per day appear safe (9).

Reported side effects tend to be minor and include nausea, upset stomachs, mild skin rashes, increased acne, headaches and heavy menstrual flows (41).

However, pregnant and nursing women should avoid Vitex, as its effects on babies haven’t been well studied (42).

Researchers also believe that Vitex may interact with antipsychotic medications, birth control pills and hormone replacement therapy. Therefore, you may want to discuss Vitex with your doctor before taking it (9).

Summary Vitex agnus-castus has mild and reversible side effects and is considered safe for most people. However, pregnant or nursing women, as well as individuals using certain types of medications, may want to abstain.

Vitex agnus-castus (chasteberry) may boost fertility and reduce symptoms of PMS and menopause. It may also repel certain insects and battle some types of cancer.

Most other uses are currently unsupported by science.

It may cause stomach discomfort and other mild side effects but is considered safe for most people.

If you’d like to give Vitex agnus-castus a try, it’s best to discuss its use with your doctor — especially if you’re pregnant, nursing or taking certain prescription medications.