Cassia is used in traditional Chinese medicine, where it is considered one of the 50 fundamental herbs.
A 2003 study published in the DiabetesCare journal followed Type 2 diabetics ingesting 1, 3 or 6 grams of cassia daily. Those taking 6 grams shows changes after 20 days, and those taking lesser doses showed changes after 40 days. Regardless of the amount of cassia taken, they reduced their mean fasting serum glucose levels 18–29%, their triglyceride levels 23–30%, their LDL cholesterol 7–27%, and their total cholesterol 12–26%, over others taking placebos.
The effects, which may even be produced by brewing a tea from cassia bark, may also be beneficial for non-diabetics to prevent and control elevated glucose and blood lipid levels. Cassia's effects on enhancing insulin sensitivity appear to be mediated by polyphenols ]. Despite these findings, cassia should not be used in place of anti-diabetic drugs, unless blood glucose levels are closely monitored and its use is combined with a strictly controlled diet and exercise program.
There is also much anecdotal evidence that consumption of cassia has a strong effect in lowering blood pressure, making it potentially useful to those suffering from hypertension. The USDA has three ongoing studies that are monitoring the blood pressure effect.
Though the spice has been used for thousands of years, there is concern that there is as yet no knowledge about the potential for toxic buildup of the fat-soluble components in cassia, as anything fat-soluble could potentially be subject to toxic buildup. There are no concluded long term clinical studies on the use of cassia for health reasons.
European health agencies have warned against consuming high amounts of cassia, due to a toxic component called coumarin.