Previous studies on healthy subjects have shown that the intake of 6 g Cinnamomum cassia reduces postprandial
glucose and that the intake of 3 g C. cassia reduces
insulin response, without affecting postprandial
glucose concentrations.
Coumarin, which may damage the liver, is present in C. cassia, but not in Cinnamomum zeylanicum. The aim of the present study was to study the effect of C. zeylanicum on postprandial concentrations of plasma
glucose,
insulin, glycaemic index (GI) and insulinaemic index (GII) in subjects with
impaired glucose tolerance (IGT). A total of ten subjects with IGT were assessed in a crossover trial. A standard 75 g oral
glucose tolerance test (OGTT) was administered together with placebo or C. zeylanicum capsules. Finger-prick capillary blood samples were taken for
glucose measurements and venous blood for
insulin measurements, before and at 15, 30, 45, 60, 90, 120, 150 and 180 min after the start of the OGTT. The ingestion of 6 g C. zeylanicum had no significant effect on
glucose level,
insulin response, GI or GII. Ingestion of C. zeylanicum does not affect postprandial plasma
glucose or
insulin levels in human subjects. The Federal Institute for Risk Assessment in Europe has suggested the replacement of C. cassia by C. zeylanicum or the use of aqueous extracts of C. cassia to lower
coumarin exposure. However, the positive effects seen with C. cassia in subjects with poor glycaemic control would then be lost.