Educational information, not medical advice — ask your doctor or midwife.
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Jakyak is the dried root of the peony plant, Paeonia lactiflora. It is one of the most used herbs in Korean traditional medicine. Herbalists give it for cramping pain, period pain and gut cramps.
It is rarely used alone. The best known mix is Jakyakgamchotang, which joins Jakyak with licorice root for muscle cramps. In Korea it is most often boiled into a tea.
The short verdict on evidence: the tradition is deep, the proof is thin. The few human trials are small, and most test herb mixes rather than the root by itself. A long history of use is not proof that a herb works, and that caveat applies to everything on this page.
The main idea is that Jakyak eases cramp. Lab and animal work shows that paeoniflorin, its main compound, can relax smooth muscle (the muscle in the gut, womb and blood vessels). It may also damp down the nerve signals that make a muscle seize up.
Some lab work points to a mild calming and anti-inflammatory (swelling-easing) effect. There is also early work on how it changes male-type hormones in women. None of this has been pinned down in people.
In Korean traditional thinking, Jakyak is said to "nourish the blood" and soften a tight liver system. That is a traditional idea, not a lab finding, and the two should not be mixed up.
Jakyak is sold as the dried, sliced root. In Korea it is most often simmered in water to make a strong tea, called a decoction. A herbalist usually adds it to a mix of several other herbs.
You can also buy it as a powder, as granules you stir into hot water, in capsules, or as a liquid extract. Some products list a set amount of paeoniflorin, most do not. Choose a seller who names the plant as Paeonia lactiflora on the label and tests batches for lead and other heavy metals.
Jakyak has been in use for close to two thousand years. It appears in the oldest Chinese herb texts, then in Korea's own great medical work, the Donguibogam, published in 1613. It is a staple of Korean, Chinese and Japanese herbal practice, which places it at the top traditional tier.
See a doctor if cramps keep coming back, wake you most nights, or come with swelling, numbness or weakness in a limb. Get help the same day for severe or sudden belly pain, heavy or unusual bleeding, black stools, or bruises you cannot explain. Stop the herb and get urgent help if your face, lips or throat swell, or if you get a spreading rash or trouble breathing. Period pain that stops you working, or periods that change a lot, should be checked rather than treated with herbs.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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