The use of cesium chloride (CsCl) as an alternative treatment for cancer poses serious health risks. This is the conclusion drawn by seven honours students from UMC Utrecht in the journal Cardiovascular Toxicology. Their analysis shows that the use of cesium often leads to dangerous heart rhythm disturbances, with approximately a quarter of patients even dying as a result. The study demonstrates that the supposed effectiveness of cesium chloride is based on flawed research from the 1980s, while the health consequences can be potentially life-threatening.
Marcel van der Heyden
Supervisor Marcel van der Heyden of UMC Utrecht explains: “When we wondered why people ingest cesium—a salt that can be easily purchased online—we discovered it is often used as an alternative cancer therapy.” This so-called ‘high pH therapy’ emerged in the 1980s and is based on highly questionable science. The original studies underpinning this treatment have never been reproduced by other researchers; even the U.S. FDA explicitly warns against the use of cesium. Nevertheless, private clinics, diet books and websites persistently refer to these outdated articles as supposed scientific evidence. Van der Heyden adds: “Last summer, we contacted the journal that published this misinformation at the time, but were told the articles would remain accessible for now. Hopefully, that will change soon.”
The students’ analysis shows that three-quarters of the patients described showed clear abnormalities on an ECG, including disrupted electrical activity (QT prolongation). Both extremely slow and dangerously fast heart rhythms were identified, and several patients suffered heart attacks. Numerous other side effects were also frequently reported, including nausea, diarrhea, and epileptic seizures.
Cesium chloride is available online without a prescription, sold as pills or powder. It is promoted through websites, private clinics and books as a cancer treatment but is not prescribed by medical professionals. Once ingested, the salt spreads through the body via the bloodstream and blocks potassium channels that are essential for electrical signaling in cells. This mechanism explains the severe side effects, especially those affecting the heart.
This new research underscores the need to safeguard scientific integrity. Van der Heyden stresses the broader importance of reliable science: “As scientists, we have a major responsibility to share accurate and careful knowledge. It is valuable that our students learn early in their education what the impact of scientific misinformation can be—especially because the spread of misleading or false information about medical treatments can have immediate, serious and sometimes fatal consequences for patients.”
Read the publication in Cardiovascular Toxicology >