Cascara Sagrada: Traditional Bark for Digestive Support

Cascara Sagrada — Spanish for "sacred bark" — is the dried, aged bark of Frangula purshiana (also classified as Rhamnus purshiana), a large shrub or small tree native to western North America, ranging from southern British Columbia south to central California and eastward to northwestern Montana. The tree grows 4.5–12 meters tall with a trunk 20–50 cm in diameter, and only its bark is used for its traditional health-supporting properties.

The name was bestowed by Spanish colonists in the 17th century who learned of its use from local Indigenous tribes, including the Nlaka'pamux, Salish, and Kwakwaka'wakw peoples. For these cultures, the bark was a cornerstone of traditional medicine, primarily used to support bowel function and relieve occasional constipation. Tribes such as the Quinault, Shaker, and Stl'atl'imx also adopted Cascara Sagrada bark for various digestive complaints.

Following its introduction to formal U.S. medicine in 1877, Cascara Sagrada quickly replaced the berries of R. catharticus as the favored laxative, and by 1890 it had officially entered the Pharmacopeia of the United States. Today, following the FDA's 2002 reclassification, Cascara Sagrada is available as an herbal supplement rather than as an over-the-counter drug.

One critical preparatory detail sets Cascara Sagrada apart from nearly all other botanical medicines: the bark must never be used fresh. Fresh bark contains free anthrone, which can cause severe vomiting. The bark must be aged for at least one year or treated with heat and aeration before use. It is collected from wild trees in the spring or early summer, when it peels easily from the trunk and branches.

Cascara Sagrada bark contains 6–9% anthracene derivatives, the active laxative constituents. Of these, 60–70% are cascarosides A, B, C, and D — compounds with both O- and C-glycoside linkages. The bark also contains free anthraquinones such as aloe-emodin, chrysophanol, and emodin, along with resins, tannins, lipids, linoleic acid, and syringic acid.

Research suggests that after oral administration, the hydroxyanthracene glycosides pass through the upper intestine unabsorbed. In the colon, intestinal bacteria hydrolyze them into pharmacologically active metabolites. This explains why healthy bacterial flora may be required for full therapeutic potential and why the laxative effect typically takes 6–12 hours to occur.

Studies indicate that the mechanism of action is twofold. First, there is stimulation of colonic motility — increased propulsion and accelerated transit that reduces fluid absorption from the fecal mass. Second, the active metabolites promote secretion of water and electrolytes into the intestinal lumen while inhibiting their reabsorption from the large intestine, increasing bowel content volume and strengthening intestinal dilatation pressure to stimulate peristalsis.

Research also suggests that anthraquinone glycosides promote peristalsis through effects at the myenteric plexus, directly stimulating nerve endings in the intestinal wall. The emodin glycoside contributes to this laxative action after being metabolized to its active aglycone by intestinal flora, possibly increasing the excitability of smooth muscles in the intestinal wall.

Cascara Sagrada has traditionally been used by adults seeking occasional digestive support, particularly those dealing with occasional constipation that has not responded to dietary changes or bulk-forming approaches. German health authorities restricted herbal anthranoid laxatives specifically to constipation that has not responded to bulk-forming therapy, and the WHO (2002) monograph confirms the traditional laxative use.

It may also appeal to those interested in supporting their body's natural elimination pathways as part of a colon cleansing routine. Cascara Sagrada bark contains anthraquinones that stimulate bowel contractions and promote intestinal cleansing, and it has historically been a staple ingredient in whole-body colon cleanse formulations.

Traditional uses extended beyond constipation alone. Historically, Cascara Sagrada was used for dyspepsia, digestion-related headaches, loosening stool for conditions such as hemorrhoids, and as a bitter digestive tonic. However, these traditional applications have not been validated by modern clinical trials.

Important: Who Should Not Use Cascara Sagrada

Cascara Sagrada is contraindicated in children younger than 10–12 years (depending on the regulatory authority). It should be avoided during pregnancy, as anthraquinone glycosides are considered overly stimulating and may lead to sympathetic uterine stimulation. Nursing mothers should also exercise caution, as anthranoids can be distributed into breast milk.

People with intestinal obstruction, spastic constipation, acute intestinal inflammation, abdominal pain of unknown origin, or inflammatory diseases of the colon — including ulcerative colitis, irritable bowel syndrome (IBS), and Crohn's disease — should not use Cascara Sagrada. If you have any underlying health conditions or take medications, our naturopath is available for a free consultation to help you determine whether Cascara Sagrada is appropriate for your needs.

Take 2 capsules with a meal once daily.

A laxative effect should be allowed at least 6 to 12 hours to occur. According to the source literature, the optimal dosage is the smallest dose required to produce a soft-formed stool, and stimulant laxatives should only be used if occasional constipation cannot be improved by a change of diet or the administration of bulk-forming laxatives.

Use for more than 10 consecutive days is not recommended, as prolonged use can lead to dependence on laxatives for a bowel movement to occur. The consumption of Cascara Sagrada in higher doses is not recommended for more than 6 days because it has been associated with the development of hepatitis in rare cases.

Safety Notes to Keep in Mind

Cascara Sagrada may cause urine to turn reddish-brown or bright yellow. This change in color is harmless and should resolve after stopping use. Long-term use can result in electrolyte disturbances — particularly low potassium — characterized by weakness and fatigue. Depending on dose, it can also produce abdominal discomfort and cramps or nausea.

Long-term cascara use may lead to potassium deficiency, which can potentiate the effects of cardiac glycosides (e.g., digoxin), antiarrhythmics, corticosteroids, and certain diuretics (e.g., hydrochlorothiazide, furosemide). Cascara Sagrada also interacts with warfarin, other laxatives, licorice, and herbs with laxative properties such as aloe, rhubarb, and senna. Due to decreased intestinal transit time, cascara may potentially interfere with the absorption of practically any medication.

If you have questions about potential interactions with your current medications or supplements, we encourage you to take advantage of our free naturopathic consultation — our naturopath can help you navigate these considerations with personalized guidance.

Beyond its well-established traditional use for digestive support, researchers have begun exploring some of Cascara Sagrada's individual constituents — particularly emodin and aloe-emodin — in laboratory settings. It is important to note that all of these findings are preclinical only (in vitro and animal model data) and have not been confirmed in human clinical trials.

In vitro studies suggest that aloe-emodin and emodin have anticancer properties in cell culture and animal models. For example, a 2002 study published in Life Sciences found that aloe-emodin inhibited cancer cell proliferation and induced apoptosis in two human liver cancer cell lines. Emodin has also been studied in models of hepatocellular, breast, oral, and lung cancer. However, lab results often do not translate to effectiveness in humans, and clinical trials have not yet been conducted.

In vitro evidence also suggests that aloe-emodin may inhibit the replication of certain enveloped viruses, including herpes simplex virus, influenza virus, and human cytomegalovirus. Emodin has demonstrated antiviral activity in cell culture against several viral species including SARS-CoV and SARS-CoV-2. Again, no clinical trials in humans have evaluated Cascara Sagrada or its constituents for antiviral purposes.

Additional in vitro studies suggest that emodin may have hepatoprotective, neuroprotective, and anti-osteoporotic properties. In one preclinical study, emodin was shown to suppress osteoclast differentiation and bone resorption. None of these effects have been demonstrated in human trials, and they should not be interpreted as established health benefits of Cascara Sagrada supplementation.