Many of Rehmannia’s health benefits stem from its ability to function as an adaptogen – this is a herb that can bring calm in times of stress, give energy when tiredness threatens to take over and bring clarity of mind in times of confusion. These clever plants are able to modulate the release of stress hormones from the adrenal glands, helping to restore innate immune function whilst helping the body to adapt to various different stressors.
Rehmannia is particularly effective in supporting adrenals that have suffered due to hypo or hyper-thyroidism (a disease that is reaching epidemic proportions in the Western world). The root is rich in phytochemicals known as “iridoid gylcosides”, in particular caltalpol, which is the most studied compound of this herb. Caltapol has been shown in various studies to stimulate the production of adrenal cortical hormones and exert an anti-inflammatory effect on the body.
In contemporary herbalism, Rehmannia is known as a “trophrestorative” for the adrenals, meaning it literally restores the adrenal glands and gently nourishes them back to health. It is especially indicated in recovery from long lasting illness and nervous system burnout.
According to Traditional Chinese Medicine, yin deficiency in the kidneys is closely associated with adrenal fatigue and exhaustion. Rehmannia is classified in TCM as a blood tonic and a kidney yin tonic. It is thought to stimulate the production of the kidney hormone erythropoietin, which acts on the bone marrow to stimulate the proliferation of precursor cells and their maturation into erythrocytes (a type of red blood cell).
Rehmannia has also been found to increase renal blood flow, which in some cases has allowed renal values to return to normal. Abnormally high renal values are associated with kidney disease and sluggish kidney function.
Whilst it has a history of traditional use to relieve menopause symptoms, a few studies are now confirming Rehmannia’s effectiveness in combating night sweats and hormone disruptions. Its star phytonutrient, caltalpol, appears to be responsible for many menopausal benefits due to its ability to stimulate the adrenal cortical hormones. These hormones are responsible for the production of sex hormones which alleviate hot flushes, night sweats and vaginal dryness. The cooling and yin balancing properties of this herb are also believed to be responsible for its ability to combat hot flushes and night sweats.
Another worrying symptom for menopausal women is and increased risk of bone density loss. Several research studies have shown that Rehmannia controls bone loss to a great extent. In an animal model, Rehmannia prevented osteoporotic bone loss induced by ovariectomy (to induce menopause). Rehmannia alleviated the decrease in the trabecular bone mineral density (the mesh used to build bones), and increased cortical bone thickness and trabeculation of the bone marrow spaces. In the study, this herb not only prevented bone loss, it increased the bone matrix and thickness of bones.
Rehmannia contains many bioactive compounds with strong antioxidant activity, protecting the body against the oxidative damage that is indicated in many heart complaints. Research shows that it can also support healthy blood glucose levels which are already within the normal range which helps further promote cardiovascular health.
Folklore and history
First mentioned in Chinese medical literature during the Han Dynasty (200 BCE), Rehmannia's Chinese name, Sheng Di huang, translates as "Big Yellow" or "Fresh Yellow Earth". The species name "glutinosa" comes from "glutinous", and refers to its sweet sticky nature that is said to help calm and settle Qi, helping to draw it downward so Qi can rise again in its more natural and regular pathways.
Rehmannia root was traditionally prepared by steaming it ten times and drying it in the sun nine times. In TCM the root is often steamed in wine until both the insides and outsides turn black and moist. When the herb is charred it is used to staunch bleeding.
Also known as "the kidney's own food", Rehmannia has long been used as a kidney tonic and overall tonic for health, balance and wellbeing
With a history of use stretching back at least 2,000 years, the root of Rehmannia is counted as one of the 50 most important herbs in Traditional Chinese Medicine. Most notably, Rehmannia is considered the number one herb for disorders related to the kidneys and adrenal glands. It is considered to be a cooling herb that has the ability to balance the “yin”, and is renowned as a longevity herb.
Traditionally, Rehmannia is used to treat anaemia, palpitations, osteoporosis and adrenal fatigue. It is thought to nourish the blood and tonify the life force (jing), and reverse premature greying hair due to blood loss.
Traditionally Taken: 2-3ml taken 2-3 times per day, or as directed by a Herbal Practitioner.
Rehmannia's active constituents include; iridoids (including caltalpol and aucubin), glycosides, phenethyl alcohol, cyclopentanoid monoterpenes, norcarotenoids, polysaccharides and oligosaccharides
Not recommended for pregnant or breastfeeding women.
Rehmannia may affect blood sugar levels. It is recommended that you consult your healthcare practitioner if you have diabetes before consuming this herb.
Do not use Rehmannia within 2 weeks either side of having surgery.
Not recommended for people who have liver disease or pre-existing digestive or immune issues.