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Rehmannia

Also known as: Rehmannia glutinosa, Rehmannia, Chinese foxglove root, Di Huang, Rehmanniae radix preparata

Overview

Rehmannia glutinosa, also known as Chinese foxglove root or Di Huang, is a perennial herb native to China and a staple in Traditional Chinese Medicine (TCM). The root, especially the processed form *Rehmanniae radix preparata*, is used medicinally. It has been traditionally used for conditions like diabetes, diabetic nephropathy, neurodevelopmental disorders, and menopausal symptoms, often as part of multi-herb formulations. The herb contains bioactive compounds, notably catalpol, believed to be a primary contributor to its pharmacological effects. Research on Rehmannia is moderately mature, with several randomized controlled trials (RCTs) and meta-analyses focusing on diabetic kidney disease and neuroprotection. While evidence is promising, many studies are based on Chinese populations and multi-herb formulas, making it challenging to isolate Rehmannia's specific effects.

Benefits

Rehmannia shows promise in managing diabetic kidney disease (DKD). A 48-week RCT involving 148 type 2 diabetes patients demonstrated that a Rehmannia-6-based formulation stabilized kidney function, improving estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) compared to standard care alone. Preclinical studies suggest that *Rehmanniae radix preparata* may alleviate symptoms of ADHD by reducing neuronal apoptosis and improving energy metabolism. Catalpol, a key compound in Rehmannia, has shown anti-diabetic and kidney-protective effects in animal models, reducing hyperglycemia and renal damage. There is also some evidence suggesting potential cardiovascular risk reduction in women with premature ovarian insufficiency (POI), but more clinical validation is needed. Most clinical evidence focuses on adults with type 2 diabetes and DKD.

How it works

Rehmannia's primary active compound, catalpol, exerts its effects through anti-inflammatory, antioxidant, and anti-apoptotic mechanisms. It modulates energy metabolism and neuronal survival pathways. The herb primarily affects renal function, glucose metabolism, and neuronal health. Catalpol influences pathways related to oxidative stress, inflammation, and apoptosis in kidney and neural tissues. Catalpol is water-soluble and orally bioavailable, though specific human pharmacokinetics require further investigation. Rehmannia is often combined with other herbs in TCM to enhance its therapeutic effects synergistically.

Side effects

Rehmannia is generally well-tolerated in clinical trials, with no serious adverse events reported. The most commonly reported side effect is mild gastrointestinal discomfort. There are no significant reports of uncommon or rare side effects in high-quality trials. While no well-documented drug interactions exist, caution is advised when combining Rehmannia with other anti-diabetic or nephroprotective agents. Contraindications are not well-established, and its use during pregnancy and lactation has not been thoroughly studied. Safety in children and pregnant women is not well established, warranting caution in these populations.

Dosage

In clinical studies, doses of processed Rehmannia root (Radix Rehmanniae Praeparata) range from 10 to 20 g/day, typically administered orally in divided doses with meals. In one referenced RCT, Rehmannia-6 granules contained 15 g/day of Radix Rehmanniae Praeparata as part of a multi-herb formula. Processed Rehmannia root is preferred for therapeutic use, and water decoction or granule forms may enhance bioavailability. The maximum safe dose is not clearly defined, but traditional use and clinical trials suggest that doses up to 20 g/day are safe. Rehmannia is often combined with other herbs in TCM formulas for synergistic effects.

FAQs

Is Rehmannia effective alone or only in combination?

Most clinical evidence involves Rehmannia as part of multi-herb formulations. More studies are needed to determine its isolated effects.

Is it safe for long-term use?

Medium-term use (up to 48 weeks) appears safe. Long-term safety data are limited, requiring caution with extended use.

When can benefits be expected?

Clinical benefits, particularly in kidney function, may appear after several months of consistent use as part of a broader treatment plan.

Can it replace conventional diabetes treatments?

No, Rehmannia is used as an adjunct to standard care for diabetes and related complications, not as a replacement.

Research Sources

https://pmc.ncbi.nlm.nih.gov/articles/PMC10564374/ – This randomized, assessor-blind, multicenter RCT involving 148 adults with type 2 diabetes and DKD found that a Rehmannia-6-based treatment stabilized eGFR and reduced UACR compared to standard care over 48 weeks. The study reported no serious adverse events, suggesting a favorable safety profile, although the multi-herb formula complicates attributing the effects solely to Rehmannia.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6204205/ – This preclinical study explored the neuroprotective effects of Rehmanniae radix preparata in ADHD models, finding that it reduced neuronal apoptosis and improved energy metabolism. These findings suggest potential therapeutic effects for neurodevelopmental disorders, but further human trials are needed to validate these preclinical results.
https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2023.1192694/full – This systematic review and meta-analysis of animal studies on catalpol, a key compound in Rehmannia, included 12 studies with 231 animals with diabetic nephropathy. The analysis found that catalpol significantly reduced hyperglycemia and renal damage markers through anti-inflammatory and antioxidant effects, suggesting a potential therapeutic role in diabetic nephropathy, although human translation requires caution.
https://www.tmrjournals.com/public/articlePDF/20220201/782f55ff35266d53b53d6ade29cbd2f4.pdf – This article discusses the application of Rehmannia in treating premature ovarian insufficiency (POI). It suggests that Rehmannia may help reduce cardiovascular risk in women with POI, but further clinical validation is needed to confirm these potential benefits.
https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2024.1426972/full – This study investigates the protective effects of Rehmannia glutinosa polysaccharide (RGP) on diabetic nephropathy (DN) using network pharmacology and experimental validation. The findings suggest that RGP can alleviate DN by modulating the PI3K/Akt signaling pathway, offering a potential therapeutic strategy for DN.