Some people have a practice of using senna leaves as a laxative or to lose weight. However, academia maintains that they do not eliminate fat. Their effect increases the loss of water and electrolytes, and when consumption is prolonged, they can affect the liver.
These risks were demonstrated during a clinical practice by Pharmacy students from the National University of Colombia (UNAL) at La Samaritana University Hospital in Bogota. They analyzed the case of a 58-year-old woman who, in an effort to lose weight, drank infusions of senna leaves (Senna alexandrina) for nearly a year.
The woman was admitted with type 2 diabetes mellitus, high blood pressure, and overweight. “She could easily obtain senna leaves at a market square. She prepared the infusion in hot water and consumed it repeatedly,” said Mariana Contreras Garcia, a final-semester Pharmacy student at UNAL, quoted in a Unimedios press release. She is carrying out her clinical practice with her classmate Maria Jose Rocha Vanegas.
The Key Lies in What Happens in the Colon
The woman did lose weight, but at a very risky cost. Senna leaves have been used as a laxative, a property that comes from compounds known as anthraquinones. When they reach the large intestine, these stimulate its movements and modify the absorption of water and electrolytes. The result is not fat burning, but more liquid inside the colon, softer stools, and more frequent bowel movements, the press release explains.
“That permanent laxative state causes the loss of fluids and electrolytes and prevents food from being properly absorbed. As a result, the person gradually loses weight,” explained Professor Ilvar Munoz Ramirez of UNAL’s Department of Pharmacy, quoted in the same document. He accompanied the students during the clinical interview with the patient as part of their practical training at the hospital.
The explanation of what happens after drinking a senna infusion lies in a short chain of chemical transformations that begins when its components reach the colon.
“Senna acts as a stimulant laxative,” explained student Rocha. “When its components reach the colon, intestinal bacteria transform them into active substances that set the intestine in motion and modify the way it handles water and electrolytes, stimulating colonic motility because they act on nerve endings.”
This means that they stimulate the contractions that help move the contents through the intestine and, at the same time, cause less water to be absorbed, allowing a greater amount to remain in the colon. In this way, stools soften and bowel movements become more frequent.
The effect occurs, on the one hand, because these substances stimulate the nerve endings involved in intestinal contractions and, on the other hand, because they reduce the absorption of water and electrolytes and promote their passage into the colon.
Plants and Natural Products Can Also Cause Harm
One of the most important conclusions follows from this explanation. In this way, stools soften, and bowel movements become easier and more frequent. This mechanism explains why senna can be useful as a laxative, but also why it should not become a drink for everyday consumption.
The intestine is not the only organ that can be affected when senna consumption becomes chronic. Student Rocha notes that some metabolites present in the plant are highly reactive and can affect hepatocytes (the main liver cells, responsible for essential functions such as processing nutrients, transforming potentially toxic substances, and producing proteins necessary for the body) by interfering with the process through which they produce the energy they need to function.
If this damage persists over time, it can compromise liver function. For this reason, chronic consumption causes very serious liver damage. These compounds can interfere particularly with the functioning of mitochondria, structures that supply the energy cells need to perform their tasks.
When the team met the patient, she had already been diagnosed with liver cirrhosis and a focal lesion in the liver. Doctors were also investigating the possibility of a hepatocarcinoma, or malignant tumor originating in the organ.
The clinical case does not prove that senna consumption caused these diseases. The review conducted during the practical training established that there was a history of prolonged consumption of the plant and that, given its known effects and the duration of consumption, this was relevant to the patient’s medical history.
The woman was discharged and was awaiting a biopsy and further medical checkups to determine the nature of the liver lesion. The case offers a lesson about how patients are approached in a country such as Colombia, where the use of medicinal plants is deeply rooted.
“An important part of our culture is using plants to heal. For this reason, pharmaceutical chemists must take each patient’s context into account and explicitly ask them about this consumption,” student Rocha emphasizes, issuing a warning: “The fact that they are plants, that they are natural products, does not mean they will not harm us.”