Cascara
Also known as: Cascara sagrada, Frangula purshiana, sacred bark, buckthorn bark, Rhamnus purshiana
Overview
Cascara sagrada is an herbal stimulant laxative derived from the dried bark of the *Rhamnus purshiana* tree, native to North America. Traditionally used to relieve occasional constipation, its primary mechanism involves anthraquinone glycosides (like cascarosides A, B, C, and D) which irritate the colon lining to promote bowel movements. While historically used and formerly FDA-approved as an over-the-counter laxative, this status was withdrawn due to insufficient evidence of safety and efficacy. It is also used for bowel preparation before procedures like colonoscopy. The research maturity level for cascara is moderate, with well-documented historical use but limited contemporary high-quality clinical trials and systematic reviews. Its primary action is as a stimulant laxative, but prolonged or high-dose use carries significant safety concerns, including electrolyte imbalance and potential liver injury.
Benefits
Cascara sagrada's primary benefit is its laxative effect, stimulating bowel movements to relieve occasional constipation. This effect typically occurs within 6 to 12 hours after oral administration. However, robust clinical trials with adequate sample sizes and rigorous methodology demonstrating statistically significant efficacy over placebo are scarce, indicating weak evidence for this benefit. There is no strong evidence to support other health benefits in humans, such as antioxidant or anti-inflammatory effects, although preliminary in vitro studies on coffee cascara kombucha have suggested potential intracellular antioxidant activity. Cascara is primarily used in adults for constipation relief; its safety and efficacy in children, pregnant, or lactating women are not well established, and its use in these populations is generally not recommended due to insufficient data.
How it works
The laxative effect of cascara sagrada is attributed to its anthraquinone glycosides, such as cascarosides. These compounds are poorly absorbed in the upper gastrointestinal tract. Upon reaching the colon, gut bacteria metabolize them into active aglycones. These aglycones then irritate the colonic mucosa, stimulating peristalsis (muscle contractions that move stool through the intestines) and increasing water and electrolyte secretion into the bowel lumen. This dual action softens the stool and promotes its passage. While primarily acting on the gastrointestinal tract, cascara also contains cardiac glycosides, which could potentially affect cardiac function at very high doses.
Side effects
Cascara sagrada is generally considered safe for short-term use at recommended doses. However, prolonged use or high doses can lead to significant adverse effects. Common side effects, occurring in over 5% of users, include diarrhea, abdominal cramping, and electrolyte disturbances, most notably hypokalemia (low potassium levels). Uncommon side effects (1-5%) include nausea and vomiting. Rare but serious side effects (<1%) include clinically apparent liver injury, which has been reported with chronic, high-dose use. Cascara interacts with several medications: it can exacerbate potassium depletion when used with diuretics, licorice, or horsetail, and may alter the effects of drugs metabolized by CYP3A4. Contraindications include intestinal obstruction, inflammatory bowel disease (such as Crohn's disease or ulcerative colitis), appendicitis, and known hypersensitivity to the plant. Use during pregnancy and lactation is not recommended due to insufficient safety data and potential risks to the fetus or infant.
Dosage
Traditional and typical dosages for cascara sagrada range from 20-30 mg of dried bark extract per day for short-term use. While a minimum effective dose is not well-established, doses above this range significantly increase the risk of adverse effects. There is no clearly defined maximum safe dose, and prolonged use beyond 1-2 weeks is strongly discouraged due to the risk of dependency, electrolyte imbalance, and potential liver injury. Cascara is typically taken at bedtime to produce a bowel movement the following morning, usually within 6 to 12 hours. It is available in various forms, including dried bark, capsules, tablets, and tinctures. Its efficacy relies on gut bacterial metabolism of its active compounds; therefore, concurrent use of antibiotics may reduce its effectiveness. No specific cofactors are required for its action.
FAQs
Is cascara safe for long-term use?
No, prolonged use of cascara is not recommended as it can lead to dependency, electrolyte imbalances (especially low potassium), and rare but serious liver injury.
How quickly does cascara work?
Cascara sagrada typically produces a bowel movement within 6 to 12 hours after oral administration, making it suitable for bedtime dosing.
Can cascara be used with other laxatives?
Caution is advised when combining cascara with other laxatives, especially stimulant laxatives, due to potential additive effects and an increased risk of hypokalemia.
Does cascara have other health benefits?
Currently, there is no strong clinical evidence to support health benefits of cascara beyond its stimulant laxative effect for constipation relief.
Why was FDA approval withdrawn?
The FDA withdrew cascara's over-the-counter laxative approval due to insufficient evidence demonstrating its safety and efficacy for widespread use.
Research Sources
- https://www.ncbi.nlm.nih.gov/books/NBK548113/ – This LiverTox review from 2017 assesses the hepatotoxicity of cascara sagrada. It concludes that while generally safe for short-term use, chronic high-dose use has been associated with rare cases of clinically apparent liver injury, emphasizing the need for caution and monitoring of liver function during prolonged use.
- https://medlineplus.gov/druginfo/natural/773.html – This MedlinePlus summary provides an overview of cascara sagrada, highlighting its known drug interactions and safety concerns. It specifically notes the risk of hypokalemia when cascara is combined with other potassium-depleting agents and mentions the withdrawal of its FDA OTC approval due to insufficient evidence.
- https://www.webmd.com/vitamins/ai/ingredientmono-773/cascara-sagrada – This WebMD review classifies cascara as a stimulant laxative and points out the lack of robust scientific evidence for its common uses, such as colonoscopy preparation. It also discusses potential interactions with CYP3A4 substrates and diuretics, reinforcing safety considerations.
- https://www.mdpi.com/2304-8158/12/9/1905 – This 2023 in vitro study investigated the antioxidant and anti-inflammatory potential of coffee cascara kombucha. While it suggests some intracellular antioxidant activity, it does not provide direct clinical evidence for the effects of cascara sagrada bark in humans.
