Wang, C. et al. A preliminary observation of preventive and blocking effect of Gynostemma pentaphyllum (Thunb) Makino on esophageal cancer in rats. Hua Xi Yi Ke Da Xue Xue Bao. 1995

In this study researchers found that rats injected with a known carcinogen developed fewer and less frequent tumors when allowed to ingest water infused with Jiaogulan. The development of cancer was also delayed by about 6 weeks suggesting to the researchers that Jiaogulan was having a direct inhibitory effect.