Shu Di Huang (Rehmannia Glutinosa) – A Comprehensive Overview

In times of drought, the crops suffer, and the autumn frost comes early.

At the end of the year, there is no food to eat, and one gathers Rehmannia from the fields.

What is it used for? To exchange for grain.

In the early morning, I go with my hoe, and by dusk, my basket is not full.

I carry it to the rich man’s house, to sell to the white-faced gentleman.

With you, I can feed the fat horse, which can illuminate the ground.

I wish to exchange horse feed for this suffering, hungry stomach.

This poem narrates the story of a farmer gathering Rehmannia to exchange for horse feed to satisfy his hunger, reflecting the tragic plight of refugees who cannot even feed their cattle during times of disaster, vividly showcasing the cruelty of the old society.

“At the end of the year, there is no food to eat, and one gathers Rehmannia from the fields.” In this line, Rehmannia is an herb known for its cooling blood and nourishing properties. In this issue, I will introduce Shu Di Huang.

Introduction

What are the four virtues? One is propriety, two is righteousness, three is integrity, and four is shame. A country has four virtues; if one is lost, it will collapse; if two are lost, it will be in danger; if three are lost, it will be overturned; if four are lost, it will be destroyed. Collapse can be corrected, danger can be stabilized, overturning can be restored, but destruction cannot be reversed. If the four virtues are not upheld, the country will perish.

Do you know the four virtues of medicine? Ginseng, Shu Di, Fu Zi (Aconite), and Da Huang (Rhubarb) are these. When illness comes, it is terrifying; only these four can help. If one hesitates, it will surely lead to mistakes. Ginseng and Shu Di are the good ministers of a peaceful world; Fu Zi and Da Huang are the good generals of a chaotic world.

Troops cannot be used for long, so good generals are used temporarily. Chaos cannot forget governance, so good ministers cannot be lacking. The Nei Jing states: “Do not neglect the doors; it is the granary that does not store.” Those who can guard will live, and those who cannot will die. Nowadays, people treat Mang Xiao (Glauber’s salt) and Da Huang as if they were safe paths, while viewing Ginseng, Fu Zi, and Shu Di as if they were snakes and scorpions, which is foolish.

Distinction

Rehmannia is also known as Qian and Di Sui. The one that sinks is precious, hence the character is written with ‘down’ entering the earth. Heavenly black and Rehmannia, above and below, the meaning and nature of Rehmannia can be seen in its usage. Its juice is deep yellow and stains the hands; its taste is sweet and does not disperse on the tongue. Sucking the essence of the earth, it is quite greedy like a wild wolf, hence the soil where it is planted becomes exhausted, and it takes ten years to become sweet, its power and virtue can be anticipated.

Rehmannia sprouts in February, initially growing low, not exceeding a foot, with leaves resembling mountain cabbage and hairy and rough, also similar to small mustard leaves but thicker, with central wrinkles like a pinch, and the stem has fine hairs, with flowers at the tips resembling small tubes and colored red-purple. There are also yellow and white varieties, with fruits forming like Forsythia, with very fine seeds that are sandy brown.

The roots resemble human fingers, varying in length and thickness, some weighing several taels. The juice is most abundant; even if it is exposed to extreme heat, it will turn moist. Those harvested in February and August are not fully mature; in August, the remaining leaves are still on the stem, and the essence has not yet returned to the root.

In February, the new sprouts have grown, and the essence in the roots has nourished the leaves. It is not as good as those harvested in January or September, which have full essence. Replanting Rehmannia results in bitter taste and thin shape, unfit for medicine. The ancients said that the floating ones are Tian Huang (Heavenly Rehmannia), the sinking ones are Di Huang (Earth Rehmannia), and those that are half floating and half sinking are Ren Huang (Human Rehmannia).

The method for preparing Rehmannia is to peel it, place it in a willow wood steamer, and steam it in a porcelain pot; after steaming thoroughly, take it out, let it cool, mix with wine, and steam again until dry, avoiding copper and iron utensils to prevent kidney damage and whitening, harming men’s essence and women’s health.

As one of the traditional Chinese medicines, Rehmannia is first mentioned in the Shen Nong Ben Cao Jing, classified as a superior product, and is a fine example of food and medicine being of the same source. Shu Di Huang is rich in nutrition and delicious. Depending on different preparation methods, it can be divided into Sheng Di Huang (Raw Rehmannia), Xian Sheng Di (Fresh Raw Rehmannia), Da Sheng Di (Large Raw Rehmannia), Gan Di Huang (Dried Rehmannia), and Shu Di Huang (Cooked Rehmannia); currently, the medical community has simplified it to Sheng Di Huang and Shu Di Huang.

Fresh Rehmannia and dried Rehmannia are used as cooling blood-clearing medicines; fresh ones are crushed and juiced, raw ones are cold, dried ones are cool, and heated ones are warm. Raw Rehmannia, when steamed and dried with wine, becomes Shu Di Huang, which does not harm the stomach.

The Ben Jing Feng Yuan states: “Shu Di Huang, using fire power to steam and dry, turns bitterness into sweetness, thus it can replenish the kidney’s original energy.” The medicinal properties change from cold to warm, and from bitter to sweet, with functions shifting from clearing heat to nourishing blood, enriching yin, and filling marrow.

The Ben Jing records: “Filling the bone marrow, promoting muscle growth, long-term use lightens the body and prevents aging.”

The Ben Cao Jing Shu praises it as “the essential medicine for nourishing the kidney, the superior product for enriching yin.” Therefore, “for any insufficiency of the organs, there is nothing that cannot be nourished.” It is commonly used for symptoms caused by deficiency of liver and kidney essence and blood, such as soreness of the lower back and knees, dizziness, tinnitus, premature graying of hair, night sweats, nocturnal emissions, and diabetes.

Shu Di Huang is also a key blood-nourishing medicine, often used for various symptoms of blood deficiency, such as pale complexion, palpitations, insomnia, and menstrual irregularities.

If insufficient, efficacy is hard to achieve; if excessive, the flavor and properties are lost. The preparation of Chinese medicinal materials involves soaking, steeping, roasting, simmering, frying, and steaming; it is not to be taken lightly. The preparation of Shu Di Huang, known as “nine steams and nine dries,” is particularly special; this method requires selecting high-quality Rehmannia, which, after refinement and soaking, is steamed nine times and dried nine times in a copper pot and copper cage, totaling 80 processes and taking a month to complete.

Preparation

The specific method is to wash Sheng Di Huang, add pure yellow wine in a certain proportion, mix well, and seal the container;

Allow Sheng Di Huang to absorb the yellow wine completely, then heat and steam;

Collect the juice that flows out during steaming, steam until Shu Di Huang appears dark and void, take it out and let it dry for a day;

Mix in the collected Shu Di juice and yellow wine, steam for another day, and take it out;

Dry for another day, repeating this process nine times until it is “black as lacquer, bright as oil, sweet as honey, fragrant as candy” before it can be used.

Identification of Properties

Shu Di Huang is irregularly shaped, both inside and outside are pitch black, with a wrinkled and uneven surface. It is soft in texture, with a moist cross-section, and often shows shiny oily lumps in the center, with high stickiness and a sweet taste. The best quality is characterized by being plump, soft, uniformly black, and shiny.

Nature and Taste

It is sweet, slightly warm, entering the liver and kidney meridians, nourishing yin and replenishing blood.

Characteristics

All things follow the law of yin and yang, and medicines are also divided into yin and yang; Shu Di is a medicine of the yin category. It is a great tonic for kidney water, and kidney yin cannot be generated suddenly. Nourishing yin cannot seek quick effects, and yin medicines must be administered in large doses, which is precisely what Shu Di is suited for. Before the Song Dynasty, Rehmannia had five major functions: dispelling blood stasis, treating cough, strengthening the stomach, filling essence, and nourishing yin and clearing heat; now it has shrunk to the latter two.

Effects

Modern pharmacological studies show that Shu Di Huang contains rich amounts of sitosterol, mannitol, rehmannioside, rehmannin, sugars, glycosides, and various vitamins and minerals, which can lower blood pressure, reduce blood lipids, inhibit thrombosis, and improve myocardial ischemia; it also has significant blood-nourishing effects.

Additionally, Shu Di Huang has cardiotonic, diuretic, liver-protective, anti-inflammatory, antifungal, and blood sugar-lowering effects.