What is Sukjihwang?

Sukjihwang is a black, sticky herb made from a root. The root comes from a plant called Rehmannia glutinosa. Workers steam the root and dry it again and again until it turns dark and sweet.

In Korean medicine it is given to people who feel weak, pale, tired or dizzy. It is also used for night sweats, ringing in the ears, and a sore low back that comes with age. Old books say it "builds the blood" and "feeds the yin".

It is a single herb, but it is most often mixed with other herbs in a set formula. Long use is not the same as proof. Human trials on this root by itself are thin, so we rate its evidence low and its traditional standing high.

How does Sukjihwang work?

No one has shown how it works in the human body. What follows are clues, not facts.

Lab and animal work says the root holds sugars and plant compounds that may calm swelling and may shift blood sugar and blood cell counts. Steaming the root changes its make-up. The raw root is cooling and loosens the bowels; the steamed root is milder and more sweet.

In Korean theory it is a "tonic" herb. That means it is meant to top up something the body has run low on, not to attack a bug or block a pain signal. This is a way of thinking about the body, not a tested mechanism.

What forms does Sukjihwang come in?

You will meet it in a few forms:

Dried black slices, boiled in water to make a strong tea (a decoction). This is the classic way.

Honey pills and pressed tablets, often as part of a named formula such as the six-ingredient Rehmannia pill.

Powders, syrups and liquid extracts sold in bottles or sachets.

Quality varies a lot. A well-made batch is soft, shiny and black, not dusty or hard.

Where it comes from:

Chinese herb books from about 2,000 years ago already list this root. Korean doctors took it up early and kept it.

Heo Jun's Donguibogam, printed in Korea in 1613, gives it a clear role and keeps the raw root and the steamed root apart. The raw root is saengjihwang. The steamed one is sukjihwang.

It remains one of the most used herbs in Korean, Chinese and Japanese herb practice today.

What does Sukjihwang help with?

• Tiredness with pale skin and dizziness: This is the oldest and most common use. Korean texts treat it as the main job of the herb. There are no good human trials of the single herb for this, so the support is traditional only.
• Irregular or scant periods: It is a standard part of women's formulas in Korean and Chinese practice. Trials that exist test whole formulas, not this herb alone, so we cannot say what the root itself did.
• Night sweats and hot flushes: Tradition puts it in formulas for heat and sweating at night, often around menopause. Human evidence for the single herb has not been published. Talk to a doctor if sweats are new or heavy.
• Sore low back and knees that come with age: Korean theory links these aches to the kidney system and uses this root to feed it. This is a traditional idea. It has not been tested against a dummy pill in people.
• Ringing in the ears and poor hearing: A long-standing traditional use, again through the kidney idea. No trial has shown it helps ringing ears. New or one-sided hearing loss needs a doctor, not a herb.
• Dry skin and dry stools: The root is sweet and moist in character, so tradition uses it for dryness. Note the flip side: it can loosen the bowels too much in some people.

Which foods are rich in Sukjihwang?

1. No everyday food contains it: it is a medicinal root, not a grocery item
2. Korean herbal teas and tonic drinks: the steamed root is sometimes simmered into sweet health teas
3. Herbal porridges and chicken soups: in some home cooking a slice or two is added with other tonic herbs

Practical Tips:

You cannot get a useful amount from normal cooking; herbal use means a prepared tea, pill or extract.

What are the side effects of Sukjihwang?

• Loose stools or diarrhoea
• Bloating and a full, heavy feeling in the stomach
• Poor appetite
• Wind and stomach rumbling
• Nausea
• Rash or itch, rarely

Good to know:

Most people who take it in normal amounts have no trouble. Gut effects are the common ones, and they tend to fade when you stop or cut the dose.

The root is heavy and sweet, so it sits badly on a weak or damp stomach. Herbalists often pair it with a warming, drying herb for this reason.

We have no long-term safety data from trials. That is a gap, not a clean bill of health.

How much Sukjihwang should you take?

• Recommended daily: No dose has been set by trials. What follows is normal practice, not proof. In Korean and Chinese herb practice, 9 g to 30 g of the dried root per day is common in a boiled tea. It is nearly always cooked with other herbs. Pills, powders and extracts vary a lot in strength. Follow the label, and ask a trained herbalist before you go above it.
• Best time of day: Usually split into two doses, morning and early evening. Some Korean practice gives tonic teas in the morning on an empty stomach, but with food is kinder to the gut.
• With or without food: Take it with or just after food. The root is heavy and sweet, and food lowers the chance of a bloated, sluggish stomach.
• Time to effect: Tradition treats it as slow. People who report a change usually say it took 2 to 6 weeks. There is no trial evidence to confirm any time frame.
• How long to take it: Tonic herbs are usually taken in courses of 4 to 8 weeks, then reviewed. Stop and rethink if nothing has changed after about 6 weeks. Stop sooner if your stomach turns bloated or your stools turn loose.