Cascara and Cancer
Cascara use is not recommended because there are insufficient data for establishing its safety, and there have been reports of liver injury with high doses.
Cascara refers to the plant Cascara sagrada (Rhamnus purshiana), which has been used in laxative preparations since ancient times.1 Cascara is classified as an anthranoid laxative because some of its chemical constituents consist of an anthracene ring. These compounds are transported through the gastrointestinal tract unchanged to the large intestine, where they undergo metabolism by the flora. The laxative effect is the result of changes in colonic motility and absorption.
Despite the US Food and Drug Administration ruling that over-the-counter preparations with cascara should not be considered generally safe and effective or are misbranded because of insufficient data, it is readily found on the internet as a nutritional supplement.2
Though there has been some debate whether laxative use, particularly with anthranoid laxatives, is associated with an increased risk of colorectal cancer (CRC), few in-human studies have evaluated this question. The basis of the concern appears to be related to toxicology studies, which demonstrated carcinogenic potential in some animal models.3 Compounds that can be extracted from cascara, however, demonstrated anticancer activity in vitro and in animal models.
In-Human Studies of Cascara
Human studies of cascara are limited to prospective observational or case control studies of nonfiber or anthranoid laxatives and the risk of colon pathologies.
Two studies found no association between anthranoid laxative use and the development of aberrant crypt foci, colorectal adenomas, or CRC.4,5 A study that evaluated fiber and nonfiber laxatives, however, found that nonfiber laxatives increased the risk of CRC in a dose-dependent manner (< 5 uses per year: hazard ratio [HR], 1.49; 95% CI, 1.04-2.14; ≥ 5 uses per year: HR, 1.43; 95% CI, 0.82-2.28; Ptrend = 0.05).6 This study did not describe the laxatives included in the classification of nonfiber.