Senna

What is senna?

Senna refers to the leaves and pods of several Senna (formerly Cassia) species, mainly Senna alexandrina, also called Alexandrian or Tinnevelly senna. The plant is native to North Africa, the Middle East and India and has been used as a laxative for centuries. Senna is the active ingredient in common over-the-counter laxatives and is also found in many “detox,” “dieter’s” and “slimming” teas.

Its active compounds are anthraquinone glycosides called sennosides. They pass through the stomach and small intestine largely unabsorbed until gut bacteria in the colon convert them into active forms that stimulate the bowel.

What the research says

Constipation

Senna is effective for short-term constipation. In a double-blind, placebo-controlled trial, 90 adults with chronic constipation took senna (1 gram a day), magnesium oxide or placebo for 28 days. Overall improvement was reported by 69% of the senna group compared with 12% of the placebo group, with more spontaneous bowel movements and better quality of life scores and no severe treatment-related side effects (Morishita et al., 2021).

How it works

According to LiverTox, the National Institutes of Health liver injury database, colonic bacteria convert sennosides into rhein and rhein-anthrone, which act as local irritants on the colon to promote contractions and evacuation. They also increase the water content of stool by reducing water and electrolyte reabsorption (LiverTox: Senna).

Weight loss

There is no good evidence that senna causes fat loss. Any drop on the scale after using a senna tea reflects emptied bowels and lost water. Using laxatives for weight control can lead to dehydration and electrolyte problems and is a recognized feature of disordered eating.

Safety

LiverTox describes senna as generally safe and well tolerated at recommended doses, but says it is recommended for short-term use only, less than one week. The typical dose is 15 to 30 mg of sennosides twice a day. Side effects include abdominal cramps and electrolyte imbalance, and long-term use or abuse can lead to a “cathartic colon” with diarrhea, cramps, weight loss and darkened pigmentation of the colon lining. Several cases of clinically apparent liver injury have been described with longer, higher-dose use, usually after 3 to 5 months, and they generally resolved after stopping (LiverTox: Senna).

How it’s used in supplements

Standardized senna laxatives state the sennoside content per tablet, which makes dosing predictable. Herbal teas and blends usually do not, so the amount of sennosides per cup can vary widely with the product and how long the tea is steeped. Senna tea is typically taken in the evening, with a bowel movement the next morning.

Practical cautions:

• Use it for occasional constipation only, for no more than about a week unless a clinician advises otherwise.
• Avoid it in children, during pregnancy unless advised by a clinician, and with inflammatory bowel disease, unexplained abdominal pain or suspected bowel obstruction.
• Low potassium from laxative use can increase risks with diuretics, corticosteroids, licorice and heart medications such as digoxin.
• Persistent constipation, blood in the stool or a change in bowel habits deserves a medical evaluation.