Vitex Agnus-Castus

This is one of the herbs our naturopaths are asked about most for premenstrual symptoms, and the chat in store nearly always starts with what else you're taking.

A good fit if

• You get premenstrual tension, or breast tenderness and pain in the days before your period
• You're not on the pill or another hormonal medicine, or you've already checked with your doctor about taking them together
• You can give it two to three menstrual cycles before deciding whether it's working
• You're an adult and you're not pregnant or breastfeeding

Check with us first if

• You take the contraceptive pill, or use a hormonal IUD, an implant or HRT. The Australian label carries a required warning that chaste tree may affect hormones and medicines like these.
• You take an antipsychotic, metoclopramide or another medicine that affects dopamine. Chaste tree's diterpenes act on the same receptor these medicines target.
• You take bromocriptine, cabergoline or another dopamine agonist, for the same reason.
• If you take prescription medicine, check with your doctor, pharmacist or our naturopaths before you start.

• Standardised extract, defined mg. Best known for: The concentrated form used in almost every clinical trial. Absorption: No study has measured how well any form of chaste tree is absorbed. Typical use: Trials used around 20 to 40 mg a day, taken for about three months.
• Low-mg concentrated tablet. Best known for: A very small mg number, because the extract behind it is highly concentrated. Absorption: Not known, the same as every other form here. Typical use: One trial used 3.2 to 4.8 mg a day for breast pain.
• Herb-equivalent dry fruit tablet. Best known for: The common label in Australian shops. It states the weight of raw dried berry, not the extract. Absorption: Not known. Typical use: No trial we hold labelled doses this way, so compare products by extract type, not the mg number on the front.
• Liquid extract or tincture. Best known for: Measured in mL, usually in water, traditionally as a single morning dose. Absorption: Not known. Typical use: A long tradition in European and English-speaking herbal practice, though no trial we hold tested a liquid.
• Combination women's formula. Best known for: Chaste tree alongside other herbs or nutrients, such as green tea, B6 or fennel. Absorption: Not known for any blend. Typical use: Results from a combination trial can't be credited to chaste tree on its own.

Reference values. None. Chaste tree is a herb, not a nutrient, so the NHMRC sets no recommended intake for it.

Typical supplemental range. The best evidence is for 20 to 40 mg a day of a standardised extract, taken for about three months. Australian labels often show the equivalent weight of dried fruit instead, which runs into the hundreds or thousands of milligrams. That's a different number from the extract weight, and the two can't be compared directly, so compare like with like.

Upper level. None set. Australia's permitted ingredients list (Schedule 1) records no maximum daily dose for Vitex agnus-castus.

Worth knowing. Give it two to three full menstrual cycles before deciding whether it's working. What you need depends on your age, diet and health, so talk to one of our naturopaths.

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You take the contraceptive pill or another hormonal medicine (hormonal IUD, implant, HRT). Australian labels must warn that chaste tree may affect hormones and medicines like these.
• You take dopamine agonists (such as bromocriptine or cabergoline) or dopamine antagonists (such as antipsychotics or metoclopramide). Chaste tree acts on the same D2 receptor in the brain.
• You're pregnant. The safety review says to avoid chaste tree, so don't take it.
• You're breastfeeding. The safety review says to avoid it; experts disagree on whether it raises or lowers milk supply.
• It's for a child. We found no evidence on use in children.
• Watch for side effects: nausea, headache, gut upset, period changes, acne, itching or a rash. They're usually mild and go away.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.