Rehmannia (Rehmannia glutinosa) is a popular plant that has been used in Asian herbal medicine for centuries and is still used across the world today, including in the U.S., as a complementary approach to help support optimal health.
What is Rehmannia?
Rehmannia glutinosa is a perennial medicinal herb in the Scrophulariaceae family native to China, Japan, and Korea. The genus name “Rehmannia” honors botanist Joseph Rehmann (1788-1831), while “glutinosa” means glutinous, sticky, or glue-like, referring to the sticky leaves, stems, and roots. The plant, which can grow up to 15-30 cm in moist sandy or loamy soil, also has foxglove-like yellow-brown or violet bell-shaped flowers, which have both male and female organs and are pollinated by insects. (1, 2)
The Rehmannia glutinosa plant, a staple in Oriental herbal medicinal formulations, is also called Sheng Di Huang (as a fresh or dried herb) or Shu Di Huang (meaning cooked earth yellow in Chinese) when prepared to be eaten. It is popular in Traditional Chinese Medicine (TCM), in Japan (where traditional herbal medicine is called Kampo), and in Korea, where it is usually used as a tonic to support the healthy functioning of the blood and brain, among other potential health benefits.
Rehmannia is actually a genus of six species of flowering plants in the order Lamiales, which are native to China. The species include: Rehmannia glutinosa, Rehmannia chingii, Rehmannia elata, Rehmannia henryi, Rehmannia piasezkii, and Rehmannia solanifolia. (3) For the purpose of this article, we’ll focus on Rehmannia glutinosa, because it is one of the 50 fundamental herbs used in Chinese herbalism. It is not to be confused with Chinese foxglove (Rehmannia elata), which is an entirely different plant. (4)
How Does It Work?
The parts of the Rehmannia glutinosa plant used in herbal formulations are most often its tuberous roots, which contain over 70 active compounds that include a variety of amino acids, vitamins A, B, C, and D, polysaccharides, and other compounds. The main bioactive constituents in the plant are known as iridoid glycosides – natural plant-based molecules that are thought to slow the natural aging process, support the health of brain neurons, and support some anti-inflammatory activity, which has been demonstrated in various studies, especially after hydrolysis (breaking a molecular bond using water). However, further clinical research is needed. (5, 6)
Rehmannia root contains more than 30 iridoid glycosides (including catalpol, aucubin, geniposidic acid – also called GPA, rehmanniosides A, B, C, and D, and rehmaglutosides A–K). (7) Rehmannia root can be prepared fresh, dried, steamed, boiled, roasted, or charcoaled. It includes irregularly shaped, gnarled and slightly flat brownish-black pieces that taste bitter, yet slightly sweet. (8)
According to the research cited below, the potential benefits of rehmannia root may include supporting optimal health as a multipurpose tonic, supporting a healthy immune response during seasonal health challenges, supporting bone health, and supporting cardiovascular system health and blood circulation. It may also support adrenal gland health, digestion, balanced hormone levels already in the normal range, and temporarily relieve minor symptoms related to the menstrual cycle and other aspects of female sexual health.
Some people also use the leaves of the plant, which contain some important bioactive compounds, including different types of iridoid glycosides, and may serve as a topical application to promote healthy appearance of the skin. The flowers are not used medicinally but are used for decorative purposes. (9)
Brief History of Rehmannia Glutinosa
Rehmannia glutinosa (specifically the rehmannia root and rhizome) has a history of cultivation in China for more than 1,000 years. It is relied on as one of the most popular herbal tonics in Traditional Chinese Medicine (TCM).
What is Traditional Chinese Medicine?
TCM originated in ancient China, rooted in the ancient philosophy of Taoism (also referred to as Daoism). Similar herbal practices exist in Korea and Japan (where ancient herbology is called Kampo). Taoism, a philosophy based on the balance of opposite, yet complementary forces known as Yin and Yang, began as a religion in the year 142 C.E. (10)
Taoists aspire to finding unity and balance in all things and believe that all things are connected in the Tao (the Way), or the universe. Practitioners of Taoism believe this is achieved by finding harmony with nature, pursuing spiritual immortality, renewing and developing oneself, and being a virtuous person. (11)
It makes sense that since TCM is heavily rooted in Chinese Taoist beliefs that it should is based on the following ideas:
- The human body is a smaller version of its surrounding universe.
- Good health results from a balance of Yin and Yang.
- The stages of human life and how the body functions are represented by the five elements (fire, earth, wood, metal, and water).
- Balancing Qi (the energy that flows through the body) is also crucial to maintaining optimal health. (12)
Fundamentally, TCM incorporates a combination of the use of Chinese herbal products; Chinese therapeutic massage (known as tui na); a healthy diet; calming exercises dedicated to flexibility, posture, mental clarity, breathing techniques, and specific movements (such as tai chi and qi gong); acupuncture; and moxibustion (when an herb is burned above the skin to apply heat to acupuncture points).
Chinese herbal medicine uses various minerals, animal products, and plants as medicinal substances, including the leaves, roots, stems, flowers, and seeds. These ingredients are blended and formulated in teas, capsules, liquid extracts, powders, and other delivery methods. (13) In TCM, unprocessed rehmannia root is traditionally used to reduce heat in the blood, to purify elements of the blood, to nourish Yin (to help restore the bodily balance of Yin and Yang), and to promote the production of bodily fluid.
In the 1950s, Western medicine began to play a large role in Chinese medical care as well, leading to the development of integrative medicine. In some ways, especially in the U.S., TCM then became a complementary approach to modern medicine. (14)
Potential Health Benefits of Rehmannia Glutinosa
Known as a multipurpose tonic, Rehmannia glutinosa supports healthy functioning of:
- The Immune System
- Blood Glucose Levels Already in the Normal Range
- Skin and Tissues
- The Brain
- The Heart
- The Liver
- Kidneys and Adrenal Glands
- The Digestive Tract
- The Nervous System
- The Female Reproductive System
Supports a Healthy Immune Response
A study on a purified solution of Rehmannia glutinosa root found that it suppressed production of proinflammatory cytokines and enzymes, meaning that it helped to prevent some mast cell activation (the cells associated immune responses such as itching, sneezing or coughing.) These results make the root extracts a possible ingredient in formulas geared toward alleviating minor symptoms related to seasonal health challenges. (15) Another study on the boiled fresh extracted rhizome of Rehmannia glutinosa found high free radical scavenging (antioxidant) activity in the plant, which may help people with health conditions related to AGEs (proteins or lipids that become glycated as a result of exposure to sugars, which may speed the aging process). (16)
Supports Blood Glucose Levels Already in the Normal Range
For people with irregular blood glucose levels, some people use a combination of Western medicine and TCM to support optimal health. In response, a formula of Rehmannia glutinosa and other herbs, known as Rehmannia Six Formula (RF), was tested in several clinical trials for its potential effects on blood glucose levels. Rats that took a daily dose of 2.4 mg/kg RF for 40 weeks reduced their body fat and weight ratio. Another study that lasted 32 weeks reportedly reduced plasma glucose in rats. “Although the effect of RF and its ingredients on blood glucose is not prominent, its protective effect against several diabetic complications is more impressive in both in vivo and in vitro models.” (17) With Rehmannia glutinosa having lowered plasma glucose levels, it is believed that the supplement may have increased glucose utilization through increase of beta-endorphin secretion from adrenal glands. (18)
Supports Healthy-Looking Skin
A different study on rats investigated one of the active ingredients in rehmannia root known as geniposide, an iridoid glycoside. The study found that geniposide helped protect cells against hydrogen peroxide-induced oxidative damage, which could be a factor in supporting healthy-looking skin during the natural aging process. (19) In addition, although the root of the plant is most commonly used in herbalism, its leaves are also sometimes used. For instance, it has been reported that he leaves may be applied topically as a compress to help soothe itchy or red skin. (20)
Supports Bone Health
In traditional folk medicine, the leaves are not used as much as the dried Rehmannia glutinosa root. For some, the root is used as a kidney-tonifying herb to support joint health. In a study on aging rats, it was found that extracts of dried rehmannia root were able to prevent some bone loss without influencing hormones such as estrogen. These are promising results that could be further tested in human clinical trials to promote bone health. (21)
May Support Brain Health
According to the theory of TCM, the health of the brain is nourished by the kidneys. Phlegm obstruction of the channels may have a negative effect on cognition and memory. To counter this effect, in China, herbal compounds are used in a complementary and alternative role in preventing and treating such symptoms. As such, Rehmannia glutinosa and other Chinese herbs are believed to support cognitive function, especially as the brain ages. (22) Catapol, the most active iridoid glucoside in Rehmannia glutinosa, “has been shown to have antioxidation, anti-inflammation, anti-apoptosis and other neuroprotective properties and plays a role in neuroprotection against hypoxic/ischemic injury.” However, more research on its effect on neurological health is needed to support this claim.(23)
Supports Heart Health
With its promising antioxidant properties from its many bioactive compounds, Rehmannia glutinosa not only helps protect the body against oxidative damage but also supports healthy blood glucose levels already within the normal range, which may also help promote cardiovascular health.
Supports Liver Health
When examining the active compounds in rehmannia, it’s important to consider the importance of geniposidic acid. For instance, a study on rats showed that geniposidic acid may play a role in supporting liver health. (24) A separate study investigated the effects of water extracted Lycium barbarum and Rehmannia glutinosa (0.05% and 0.15% for each) for eight weeks on the injured livers of rats. “After an 8-week herbal extract treatment, [the rats’ livers showed] diminished necrotic hepatocytes, chemoattraction of inflammatory cells, and liver fibrosis.” (25)
Supports Kidney Health
In addition, catapol, the main active iridoid glycoside in Rehmannia glutinosa, when administered orally, was found to support kidney health in a study on rats. (26)
Supports Healthy Adrenal Glands
One of the main functions of catalpol is to stimulate the production of adrenal and sex hormones. Therefore, in Western herbal medicine, rehmannia root extract is used as an adrenal tonic, protecting the cells of the adrenal cortex and pituitary gland from oxidation during periods of prolonged stress. (27)
Supports Healthy Digestive Tract
Another study on 20 slightly obese human females aged 40–65 years, who ingested steamed Rehmannia glutinosa root for 8 weeks, “showed a significantly decreased waist circumference following the herbal treatment,” suggesting that the herbal treatment may have had a prebiotic effect by positively altering intestinal microbiota and supporting overall gut health. (28)
Supports Nervous System Health
In a randomized, placebo-controlled, double-blind clinical trial on healthy adult males, distilled Rehmannia glutinosa herbal acupuncture had a positive effect on activating the nervous system, suggesting that the herb may promote nervous system health. However, more research is needed. (29)
Supports Female Reproductive System Health
Rehmannia root is also believed to support female reproductive system health by helping to regulate and temporarily relieve symptoms related to the menstrual cycle, supporting uterine health, and more. (30, 31)
How to Shop for Rehmannia Glutinosa
Possible side effects of ingesting Rehmannia glutinosa could include bloating, nausea, or loose bowel movements and other digestive discomfort. Pregnant or breastfeeding women should not use this herb.
Chinese herbs are marketed in the U.S. as dietary supplements. To avoid potentially harmful contaminants, always buy certified organic products from trusted sources, such as Natural Healthy Concepts. And be sure to talk to your healthcare provider before trying any herbal supplements in your diet.