Cinnamon is often recommended for people with diabetes on the grounds that it helps to reduce fasting blood sugar levels. We are not scientists but we have read around the subject. The conclusions are, at best, mixed; on balance it is thought that cinnamon actually does little to reduce blood sugar levels. See here for a recent, thorough and authoritative round-up of the research by Science-Based Medicine.
However there are two points that this research fails to address. First, it is far from clear what kind of cinnamon is being used in the research. It is cinnamon cassia but probably the weaker one from China or Indonesia that is prevalent in the US, where most of the trials were undertaken. Also, knowing the differences in chemical terms between true cinnamon and cinnamon cassia one wonders whether true cinnamon could have different results. Second, the research misses the obvious point that cinnamon is often used as a sugar substitute, thus obviously reducing blood sugar levels.
PS see here for an update on this piece.