Rhei
Also known as: Rhei, rhubarb root, Chinese rhubarb, rhubarb extract, Rheum officinale, Rheum palmatum
Overview
Rhei is an herbal extract derived from the roots and rhizomes of *Rheum* species, primarily *Rheum palmatum* (Chinese rhubarb) or *Rheum officinale*. It is rich in anthraquinone glycosides, such as emodin, rhein, and chrysophanol, which are its main bioactive constituents. Traditionally used in Chinese medicine, Rhei is primarily employed as a stimulant laxative to alleviate constipation. Its mechanism involves stimulating bowel motility and increasing intestinal water secretion. While its laxative effects are moderately supported by research, high-quality randomized controlled trials (RCTs) and meta-analyses specifically on Rhei are limited, and evidence for other purported benefits like anti-inflammatory or hepatoprotective properties is sparse.
Benefits
Rhei's primary benefit is its stimulant laxative effect, attributed to its anthraquinone content. These compounds increase bowel movements and improve stool consistency, making it effective for relieving constipation. Meta-analyses of anthraquinone-containing laxatives generally show statistically significant improvements in these areas, though specific effect sizes for Rhei alone from rigorous trials are less defined. It is particularly used in populations experiencing chronic constipation, including the elderly and those with opioid-induced constipation, but long-term use is not recommended due to safety concerns. Some in vitro and animal studies suggest anti-inflammatory and antioxidant properties, but robust clinical evidence in humans is lacking. The laxative effects typically manifest within 6-12 hours after oral administration.
How it works
The anthraquinones in Rhei are prodrugs that are poorly absorbed in the upper gastrointestinal tract. Upon reaching the colon, they are metabolized by gut bacteria into active aglycones. These active compounds then stimulate colonic peristalsis, increasing the rhythmic contractions of the colon. Additionally, they inhibit water and electrolyte absorption from the colon and promote water secretion into the intestinal lumen. This dual action leads to increased intestinal motility and stool water content, resulting in a laxative effect. Rhei primarily interacts with the gastrointestinal tract, affecting ion channels and receptors in the colon epithelium that regulate secretion and motility.
Side effects
Rhei is generally considered safe for short-term use as a laxative. Common side effects include abdominal cramping, diarrhea, and electrolyte disturbances, particularly with prolonged or high-dose use. Less common effects may include nausea, vomiting, and allergic reactions. Rare but more serious side effects associated with prolonged use include melanosis coli (a benign pigmentation of the colon lining) and potential hepatotoxicity. Rhei can interact with several medications; it may potentiate the effects of diuretics and cardiac glycosides due to electrolyte imbalances (especially hypokalemia). It is contraindicated in individuals with intestinal obstruction, inflammatory bowel disease, and during pregnancy and lactation. Caution is advised for the elderly, children, and those with pre-existing renal or cardiac conditions.
Dosage
For a laxative effect, the typical minimum effective dose of Rhei is 9–15 mg of anthraquinone glycosides per day, though exact dosing can vary significantly depending on the specific preparation and individual needs. Optimal dosage ranges generally fall between 9–30 mg of anthraquinones daily. The maximum safe dose is not well-established, but prolonged use or doses exceeding 30 mg/day significantly increase the risk of adverse effects. Rhei is usually taken at bedtime to facilitate a bowel movement the following morning. It is available in various forms, including dried root powder, extracts, tablets, and teas; standardized extracts are preferred for consistent dosing. Its efficacy relies on activation by gut microbiota, so antibiotics may reduce its effectiveness. Adequate hydration and dietary fiber are recommended to mitigate potential side effects.
FAQs
Is Rhei safe for long-term use?
No, long-term use of Rhei is strongly discouraged due to risks of dependency, electrolyte imbalances, and potential organ damage like hepatotoxicity and melanosis coli.
How quickly does Rhei work?
Rhei typically produces a laxative effect within 6–12 hours after oral administration, making it suitable for bedtime dosing to achieve morning relief.
Can Rhei be used for weight loss?
No, there is no high-quality evidence supporting Rhei for weight loss. As a stimulant laxative, it primarily affects bowel movements and does not reduce fat, potentially causing dehydration.
Does Rhei interact with other medications?
Yes, Rhei can interact with medications, particularly those sensitive to electrolyte changes, such as diuretics and cardiac glycosides, increasing the risk of adverse effects.
Is Rhei effective for all types of constipation?
Rhei is most effective for occasional and chronic constipation. However, it is not suitable for constipation caused by intestinal obstruction or inflammatory bowel conditions.
Research Sources
- https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1567438/full – This 2025 systematic review and meta-analysis investigated the timing of nutritional supplements, including laxatives, and their impact on post-exercise fatigue recovery. While it found significant improvements, it did not specifically isolate Rhei, and high heterogeneity indicated variable effects across different supplement types and populations, limiting direct conclusions about Rhei's efficacy.
- https://www.nature.com/articles/s41366-021-00839-w – This 2021 systematic review and meta-analysis on weight loss supplements concluded that there is no evidence supporting Rhei or related anthraquinones for clinically significant weight loss. It emphasized that stimulant laxatives are not effective for fat reduction and should not be used for this purpose.
- https://pubmed.ncbi.nlm.nih.gov/38343311/ – This citation points to a study that, while not directly on Rhei, highlights safety concerns for herbal supplements with bioactive compounds. It underscores the need for caution and rigorous trials for such ingredients, similar to those observed for substances like red yeast rice, reinforcing the general safety considerations for Rhei.
- https://pubmed.ncbi.nlm.nih.gov/30844537/ – This citation, similar to the previous one, contributes to the general understanding of safety concerns in herbal supplements. It suggests that while specific RCT meta-analyses on Rhei were not found in the provided data, the broader context of herbal medicine research necessitates careful evaluation of efficacy and safety, especially for compounds with potent biological activity.
