The Benefits and Effects of the Traditional Chinese Medicine Rehmannia, and the Differences Between Raw Rehmannia and Prepared Rehmannia
Rehmannia is a common medicinal herb in traditional Chinese medicine, and most Chinese medicines contain its ingredients. Rehmannia is further divided into fresh Rehmannia, raw Rehmannia and prepared Rehmannia; depending on the processing method, the uses also differ. So what are the benefits and effects of Rehmannia? What are the differences between raw Rehmannia and prepared Rehmannia?
I. Introduction to Rehmannia
Rehmannia, also known as bian, qi or raw Rehmannia, is a perennial herbaceous plant of the genus Rehmannia in the family Scrophulariaceae. The tuberous root of Rehmannia is one of the traditional Chinese medicines. It is harvested in autumn, with the reed head, fibrous roots and mud removed, and used either fresh or after processing. It was first recorded in the Shennong Bencao Jing (Divine Farmer's Materia Medica), and according to the processing method it is further divided in materia medica into fresh Rehmannia, dried Rehmannia and prepared Rehmannia.
Rehmannia grows 15-30 cm tall and blooms in early summer, with several large, pale red-purple flowers. Its main producing area is northern China, most famously the area around Jiaozuo City in Henan Province, such as Wen County, Bo'ai County and Wuzhi County. In ancient times Jiaozuo City was known as Huaiqing Prefecture, so the Rehmannia produced in this region is renowned for having the best effects, and is called "Huaiqing Rehmannia".
II. The Benefits and Effects of Rehmannia
Depending on the processing method, the nature, flavour and uses of Rehmannia also differ. It is mainly divided into fresh Rehmannia, raw Rehmannia and prepared Rehmannia.
1. Effects of fresh Rehmannia: clears heat and cools the blood, nourishes yin and promotes fluid production
The fresh tuberous root of the Rehmannia plant. Fresh Rehmannia is sweet and bitter in flavour and cold in nature. It clears heat and cools the blood, nourishes yin and promotes fluid production, and is used for vomiting blood and epistaxis or skin eruptions caused by warm-febrile disease or heat toxin; it can clear fire, relieve heat, cool the blood and stop bleeding.
2. Effects of raw Rehmannia: nourishes yin and relieves excessive thirst
The dried tuberous root of the Rehmannia plant. Raw Rehmannia is sweet and bitter in flavour and slightly cold in nature. It can nourish yin and cool the blood, and treats excessive thirst and warm-febrile disease that has entered the blood aspect. It mainly treats such conditions as yin deficiency with internal heat, restlessness and insomnia due to deficiency, and excessive menstruation.
3. Effects of prepared Rehmannia: nourishes and tonifies the blood
Rehmannia that has been processed by steaming is called prepared Rehmannia. It is slightly warm in nature and sweet in flavour, and enters the liver and kidney meridians. It is used to tonify the blood and nourish yin (especially kidney yin), and to benefit essence and replenish marrow. It mainly treats such conditions as kidney deficiency and yin depletion, dizziness and blurred vision, irregular menstruation, palpitations and insomnia, soreness of the lower back, spermatorrhea and abnormal uterine bleeding. The famous Siwu Tang (Four-Substance Decoction) uses prepared Rehmannia as its medicinal ingredient; only when there is blood heat or internal heat is dried raw Rehmannia used instead.
III. Usage and Dosage of Rehmannia
1. Internal use: decoct in water, 10-30g; pound to extract juice or boil into a paste.
2. External use: an appropriate amount, pounded into a paste and applied; or the juice taken and dabbed on; those with damp pathogens in the spleen and stomach or with yang deficiency should avoid taking Rehmannia;
IV. Groups Who Should Avoid Rehmannia
1. Raw Rehmannia: raw Rehmannia is cold in nature, so those with spleen deficiency and diarrhoea, or stomach deficiency and poor appetite, should avoid it; those with abdominal fullness and loose stools, and those with a cold constitution, should also try not to consume it.
2. Prepared Rehmannia: those with qi stagnation and excess phlegm, abdominal distension and pain, or poor appetite and loose stools should not take prepared Rehmannia, as it will hinder digestion; when used in large doses or over a long period, it should be used together with chenpi (dried tangerine peel), sharen (Amomum fruit) and the like, to avoid its sticky, cloying nature harming the stomach.
3. Rehmannia should not be taken together with radish, scallion white, chive white or xiebai (Allium macrostemon).
V. The Differences Between Raw Rehmannia and Prepared Rehmannia
Many people cannot tell raw Rehmannia and prepared Rehmannia apart. Although both are Rehmannia, as Chinese medicines they still differ in shape, medicinal use and properties. Specifically, there are the following three major differences:
| Shape and colour | Nature, flavour and meridians entered | Benefits and effects |
| 1. Raw Rehmannia: the colour is brownish-grey or brownish-black, relatively hard, not easy to break; the flesh of raw Rehmannia is brownish-black or pitch-black, with a slightly sweet taste; the shape is mostly irregular lumps or oblong. 2. Prepared Rehmannia: it is a processed product of raw Rehmannia, pitch-black in colour with a lustre, soft and somewhat resilient in texture; the shape is mostly irregular slices and fragments, varying in size and thickness. |
1. Raw Rehmannia is sweet in flavour and cold in nature; it enters the heart, liver and kidney meridians. 2. After processing by steaming, the nature of prepared Rehmannia changes: it is slightly warm in nature and sweet in flavour, and enters the liver and kidney meridians. |
1. Raw Rehmannia: clears heat and promotes fluid production, cools the blood and stops bleeding; often used for warm-febrile disease with heat entering the nutrient and blood aspects, high fever and clouded spirit, dry mouth and crimson tongue. 2. Prepared Rehmannia: tonifies the blood and nourishes yin, replenishes essence and augments marrow; suitable for blood deficiency with sallow complexion, dizziness, palpitations, insomnia, irregular menstruation, abnormal uterine bleeding, as well as tidal fever, night sweats, spermatorrhea, excessive thirst and other patterns of kidney yin insufficiency. |
Conclusion: The above is a relevant introduction to the benefits and effects of Rehmannia. We believe everyone now has a certain understanding and knowledge of it. Here we remind everyone that when consuming Rehmannia you must consult a doctor's advice, and prepared Rehmannia cannot be eaten directly; it can be consumed as an infusion in water, in soup, or as a decoction.