Latin: Rehmannia glutinosa
Chinese: Shu di huang (cooked)
Chinese: Sheng di huang (raw)
English: Chinese Foxglove
WHAT IT DOES: Rehmannia root strengthens and nourishes the blood and Yin, reduces inflammation, and strengthens the kidneys.
SAFETY ISSUES: Do not use single herb with indigestion, poor appetite or diarrhea. Most TCM combination products add herbs to neutralize this issue.
• Dried powder: 9-30 grams per day
• 4:1 dried decoction: three to nine grams per day
In the thick black roots of rehmannia, TCM doctors see a strong reservoir of nutrients beneficial to the kidneys and blood, and capable of removing heat and inflammation. The cooked form of rehmannia is sweet in taste and warm in action, while the raw form is sweet and bitter in taste, and cold in action. The raw form, being cold in action, is used more frequently to remove inflammation. Conversely, when you cure the root by cooking it with wine it becomes more nourishing and warm in action (Kubo et al., 1996).
Both forms are used in the treatment of deficiency diseases where the presence of heat (look for a red tongue) causes symptoms such as fever, menopausal hot flashes, and thirst. Rehmannia can be used when there is a need to generate fluids—especially with the weakness that results from prolonged low-grade fevers–and with hormonal related deficiencies of fluid as found in Sjorgren’s syndroms and dry eyes.
Rehmannia root is very thick and gummy, so it can impair digestion, which explains the contraindications listed above. It is one of the base herbs included in the highly valued Six-flavored rehmannia pill (liu wei di huang wan), also called rehmannia six formula, used as a primary treatment for Yin deficiency. I always prescribe formulas in the clinic that add herbs to neutralize this problem.
Scientific studies have shown that this herb possesses a number of interesting and complex actions. We use Rehmannia root in our clinic routinely to treat problems related with Yin deficiency, such as fatigue with heat signs, irritability, and low-grade fevers. Herbs useful for Yin deficiency are those that increases the body’s ability to absorb or use nutrients necessary for protection, regeneration and repair of any tissue. If, for example, I am using blood building herbs to get circulation to tissues, but find I need a stronger effect, adding Yin tonics helps with that, because the blood is part of Yin in TCM. This is especially true for patients over the age of 40, when hormones start to decline. For the treatment of nephritis, we often combine rehmannia root with astragalus root, shilajatu and triphala. Rehmannia root is also very useful in treating autoimmune diseases in general because of its stabilizing effects.
• Its anti-inflammatory action has been shown in animal models to reduce inflammation in the central nervous system, by affecting astrocytes–CNS immune cells (Kim et al., 1999).
• Rehmannia and astragalus root based formulas may also help reduce nephritis and its complications. In one study of 100 patients, researchers reported that their formula “was markedly effective for proteinuria, hematuria, improvement and recovery of renal functions, edema, anemia, anorexia etc. in comparison with the control group. ” (Su et al., 1993).
• Rehmannia six formula has been shown effective for protecting immune and blood cell formation as well as heart, liver and kidney function during chemotherapy (Xu, 1992).
• One interesting study done on guinea pigs showed an ability to protect against chemical induced deafness, verified by scanning electron microscope of the inner ear (Zhuang et al., 1992).
• In one study performed in China, when Yin-deficient animals were pre-treated with Rehmannia six formula, they sustained less damage to their periodontal tissues from outside trauma than the non-treated animals (Cai et al., 1990).