Daily cinnamon consumption may improve insulin sensitivity
In this featured study, investigators sought to illuminate clinical understanding of the potential efficacy of repeated cinnamon ingestion on insulin sensitivity. Solomon and Blannin acknowledge former research demonstrating cinnamon's beneficial effects on fasting glucose in humans as well as in vitro and in vivo animal studies suggesting cinnamon may reduce fasting plasma glucose (FPG). However, prior to this clinical trial, no data was available on cinnamon's effect on insulin sensitivity over the long term, nor information about what changes occur in glucose and insulin response after the removal of daily cinnamon consumption. To further clinical research, Blannin and Solomon devised a single-blind randomized cross-over design study involving eight male volunteers.
The participants in this study were aged 25 +/- 1 years, body mass 76.5 +/- 3.0 kg, with a BMI average of 24.0. All were sedentary but otherwise healthy and compliant. Each volunteer finished two 20-day interventions: a control trial with placebo and a cinnamon trial, with a two-week wash-out period in between. The cinnamon trial followed the same protocol as the control (in which subjects consumed vegi-cap wheat flour placebo pills), with the only difference being subjects consumed 6 X 500 mg cinnamon pills on days 0-14, resuming with the placebo pills the last 5 days. For both trials, participants underwent oral glucose tolerance testing (OGTT) and blood collection on days 0, 14, 16, 18 and 20. The insulin sensitivity measurement by researchers was based on plasma glucose and insulin responses to OGTT. All data underwent statistical analysis beyond the scope of this review, with a reported statistical significance of P < 0.05.
The most noteworthy findings are: 1.cinnamon ingestion reduced the glucose response to OGTT as early as day 1 vs. day 0 (-13.1 +/- 6.3%) and day 14 (-5.5 +/- 8.1% vs. day 0), and 2. insulin responses to OGTT also dropped on day 14, and researchers noted improved insulin sensitivity on day 14 compared to day 0. Though Solomon and Blannin observed improved insulin sensitivity in these inactive but healthy participants, their study showed no lasting effects once cinnamon was removed from the daily diet. To further investigate possible clinical applications for daily cinnamon consumption, researchers conclude this study stating, "Further investigation of the long term effects of cinnamon on insulin sensitivity and intramuscular insulin signaling pathways in humans is required, so that conclusions as to its potential clinical application can be made."
Study: Solomon, T., Blannin, A., Eur J Appl Physiol, Published online: 22 Jan, (2009)