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

It’s most commonly used to treat:

  • premenstrual syndrome (PMS)
  • menstrual disorders
  • infertility
  • acne
  • menopause
  • 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
  • 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 is particularly known for its ability to improve conditions affecting a woman’s reproductive system.

Eases symptoms of premenstrual syndrome (PMS)

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

These include:

  • constipation
  • irritability
  • depressed mood
  • migraines
  • breast pain and tenderness

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

In one study, women with PMS took Vitex agnus-castus during three consecutive menstrual cycles. In total, 93 percent of those given vitex reported a decrease in PMS symptoms, including:

However, the study didn’t include a control group, and placebo effects can’t be ruled out (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

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

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

In a follow-up study 52 additional pre- and postmenopausal women were given a vitex cream. Of the study participants, 33 percent experienced major improvements, and another 36 percent 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 percent of them became pregnant. In comparison, only 10 percent 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, 19).

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.

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 percent (28). However, the study didn’t include a control group, making it impossible to know whether vitex was responsible for these benefits.
  • 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). Keep in mind that essential oils should not be consumed, and vitex supplements are unlikely to reduce the risk of infections.
  • 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).
  • 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).
  • Epilepsy prevention. Animal studies suggest that vitex may reduce the likelihood of 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, but the evidence is weak. More research is needed before any claims can be made.

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, the overall evidence is weak and controversial (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. The hormone-balancing effects of vitex are sometimes claimed to boost hair growth in men. However, no research can be found to support this claim.
  • Acne treatment. Three studies assert that vitex may reduce acne faster than conventional treatments. However, these studies are decades old. 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 (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:

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, or chasteberry, may boost fertility and reduce symptoms of PMS and menopause. It may also repel certain insects.

Most other uses are currently unsupported by science.

It may cause stomach discomfort and other mild side effects, but it’s 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 first — especially if you’re:

  • pregnant
  • nursing
  • taking certain prescription medications