What is Jakyak?

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.

How does Jakyak work?

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.

What forms does Jakyak come in?

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.

Where it comes from:

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.

What does Jakyak help with?

• Muscle cramps in the legs and feet: This is the best studied use, and even here the proof is limited. Small Japanese and Korean studies looked at the Jakyak plus licorice mix in people with liver disease or on kidney dialysis, and some reported fewer cramps. The studies were small and the mix was tested, not Jakyak alone.
• Period pain: A long-standing traditional use across East Asia. Jakyak sits in many classic period-pain mixes. Human trials of the root by itself are lacking, so this rests on tradition rather than proof.
• Stomach and gut cramps: Traditional practice uses Jakyak for gripping belly pain. Animal work shows it can relax gut muscle. There is no good human trial of the single herb for this.
• Tight, aching muscles and low back spasm: Herbalists pair Jakyak with licorice for a tight, pulling ache. This use is well established in tradition. Formal testing in people is very thin.
• Polycystic ovary syndrome, PCOS (a hormone problem that upsets periods): Some early Japanese work on peony-containing mixes looked at male-type hormone levels in women with PCOS. The studies were small and hard to repeat. This is a research idea, not a proven use, and PCOS needs proper medical care.

Which foods are rich in Jakyak?

Garden peony roots are not the same thing and should not be eaten.

What are the side effects of Jakyak?

• Loose stools or mild diarrhoea
• Stomach upset or nausea
• Poor appetite
• Feeling sleepy or dull
• Skin rash or itch from an allergy
• Easier bruising, reported rarely

Good to know:

Most people who use Jakyak in normal amounts have no trouble with it. When side effects happen they are usually mild and settle once you stop. Stop and get advice if you get a rash, swelling of the face or mouth, or bruising you cannot explain.

How much Jakyak should you take?

• Recommended daily: There is no dose set by any health authority. In Korean and Chinese practice, 6 to 15 grams of the dried root per day is common, simmered in water and drunk over the day. Extracts and granules are far stronger by weight, so follow the label and start at the low end. If a herbalist made you a mix, use the amount they gave you and no more.
• Best time of day: Split the daily amount into two or three drinks across the day. For night cramps, many people take one dose in the evening.
• With or without food: Take it with or just after food. The root is drying and a bit sour, and food lowers the chance of stomach upset.
• Time to effect: For a sudden cramp, traditional use expects some easing within an hour or two. For period pain, judge it over one or two cycles.
• How long to take it: Short courses suit it best. Two to four weeks is a fair trial for cramps or period pain. If nothing has changed by then, stop and speak to a doctor or a trained herbalist rather than raising the dose.