Cascara sagrada is the dried bark of a small tree native to the Pacific Northwest, used for centuries as a natural laxative. Its name is Spanish for “sacred bark,” a term given by Spanish explorers who learned of its medicinal use from Indigenous peoples. Today it’s sold primarily as a dietary supplement for short-term relief of constipation, though its regulatory status has shifted significantly over the past two decades.
The Plant and Its Bark
Cascara sagrada comes from Rhamnus purshiana (also called Frangula purshiana), a slender deciduous tree that grows up to about 10 meters tall with thin, smooth bark that ranges from blotchy gray to reddish brown. The tree grows at low elevations from British Columbia to Northern California, mostly west of the Cascade Range, though it also appears in moist canyons as far east as Montana. The bark is harvested in spring and summer, then must be dried and aged for at least one year before use. This aging step is important: fresh bark contains compounds that cause severe nausea and vomiting. The year-long wait (or artificial aging with heat at 80 to 100°C for several hours) allows those compounds to oxidize into gentler forms.
How It Works as a Laxative
The active ingredients in cascara bark are a group of compounds called cascarosides (A through F), which belong to a broader chemical family known as anthraquinones. These compounds work directly on the smooth muscle of the colon, stimulating the nerve networks embedded in the intestinal wall. This triggers stronger contractions, the wave-like movements that push stool through. At the same time, cascarosides change how the colon handles fluids: they increase water and electrolyte secretion into the bowel and reduce reabsorption, which softens stool and adds bulk. The combined effect of stronger contractions and more fluid typically produces a bowel movement within 6 to 12 hours.
This mechanism is similar to other anthraquinone laxatives like senna and aloe. All of them act primarily on the large intestine rather than the small intestine, which is why they’re classified as stimulant laxatives rather than osmotic or bulk-forming types.
FDA Regulatory Status
Cascara sagrada was once approved as a safe and effective over-the-counter laxative ingredient in the United States. That changed in 2002, when the FDA reclassified it from “generally recognized as safe and effective” (Category I) to Category III, meaning there wasn’t enough data to confirm its safety for OTC drug use. This didn’t make cascara illegal. It simply meant manufacturers could no longer market it as an approved OTC laxative drug. Instead, cascara sagrada shifted into the dietary supplement market, where it remains widely available in capsules, teas, and liquid extracts. The distinction matters: as a supplement, it doesn’t undergo the same premarket safety review that drugs require.
Typical Dosage and Duration
Most cascara supplements are sold as dried bark extract in doses of 100 to 300 mg, with 300 mg once daily being the most common recommendation. It’s also available as a fluid extract (2 to 6 mL) or brewed as a tea. The key limitation is duration: cascara is intended only for short-term use, generally no more than one to two weeks. Health Canada’s official monograph and most clinical references agree on this ceiling. The University of Rochester Medical Center advises no more than six consecutive days.
Risks of Long-Term Use
Short-term use of cascara sagrada at standard doses is generally well tolerated, with cramping being the most common complaint. The real concerns arise with prolonged or excessive use.
The most significant risk is potassium depletion. Chronic use disrupts electrolyte balance because the colon keeps secreting potassium-rich fluid with each stimulated bowel movement. Low potassium can cause muscle weakness, heart rhythm irregularities, and fatigue. It also creates a vicious cycle: as potassium drops, the colon becomes sluggish on its own, which makes constipation worse, which tempts people to take more laxative. This dependency pattern is well documented with all stimulant laxatives, not just cascara.
Prolonged use (typically longer than two weeks) can also cause a condition called melanosis coli, where the lining of the colon turns dark brown or black. This happens because damaged colon cells release a pigment called lipofuscin, which accumulates in the tissue. It looks alarming on a colonoscopy, but melanosis coli is benign and typically reverses after stopping the laxative. Some people worry about a cancer connection because older animal studies found that long-term anthraquinone exposure caused tumors in rats. According to the Cleveland Clinic, there is no evidence that the same thing happens in humans.
Rare cases of liver injury have also been reported in people taking cascara products, though establishing a direct cause is complicated by the fact that many users take multiple supplements simultaneously.
Who Should Avoid It
Cascara sagrada is not appropriate for pregnant or breastfeeding women, children, or anyone with inflammatory bowel disease, intestinal obstruction, or unexplained abdominal pain. Because it depletes potassium, it can be dangerous for people already taking medications that lower potassium levels, including certain diuretics and heart medications. If you’re on any prescription drugs, the potential for interaction is worth checking, since potassium imbalances can amplify the effects of cardiac medications in particular.
People with chronic constipation are better served by lifestyle changes, fiber supplementation, or osmotic laxatives that don’t carry the same dependency risk. Cascara works best as a brief, occasional tool rather than a daily habit.