Cinnamon Dose-Dependently Reduces Insulin Concentration

February 27, 2009

February 27, 2009 — The ingestion of 3 g of cinnamon reduces serum insulin levels after mealtime and increases the concentration of glucagon-like peptide 1 (GLP-1), a gastrointestinal hormone that has been shown to delay gastric emptying and minimize the feeling of hunger after eating, according to a study published in the March 1 issue of the American Journal of Clinical Nutrition. There was no significant affect on blood glucose, glucose-dependent insulinotropic polypeptide (GIP), ghrelin concentration, satiety, or gastric emptying rate (GER). Furthermore, there appeared to be an inverse relationship between the amount of cinnamon consumed and the reduction in insulin concentration.

Previously, the ingestion of 6 g of cinnamon was shown to be associated with a reduction in blood glucose concentrations after mealtime, as well as GER, without affecting satiety among a group of healthy subjects. "Six grams of cinnamon is not a quantity ordinarily used in food," explains Joanna Hlebowicz, MD, from the Department of Medicine, Malmo University Hospital, Sweden, and colleagues. "[Thus,] the primary objective of this study was to determine whether adding 3 g cinnamon to a meal would change GER, satiety, or postprandial blood glucose, insulin, GIP, and GLP-1 concentrations. If this was the case, the secondary objective was to establish whether adding 1 g cinnamon to a meal would change GER, satiety, and postprandial blood glucose, insulin, GIP, and GLP-1 concentrations."

In a crossover study, a total of 15 healthy Swedish men (n = 9) and women (n = 6) were given 300 g of rice pudding with 3 g, 1 g, or no cinnamon after a period of fasting. Meals were served in random order at weekly intervals. Using real-time ultrasonography, GER was measured in each participant after meals. A scoring scale was used to determine satiety among the subjects before and after eating at prespecified intervals. In addition, venous blood samples were evaluated for the measurement of glucose, insulin, GIP, GLP-1, and ghrelin concentrations both before and after each mealtime according to the same prespecified intervals.

"This study was...designed to determine whether changes in insulin response explain lower postprandial blood glucose concentrations and whether a change in GIP, GLP-1, or ghrelin response could explain the change in insulin secretion or the change in GER in healthy subjects after cinnamon consumption," write the authors. "We also studied the dose-response relation with respect to the effect on GER, satiety, and postprandial blood glucose, insulin, GIP, GLP-1, and ghrelin responses in healthy subjects."

The results illustrated a significant reduction following the consumption of rice pudding with 3 g of cinnamon in the insulin response at 60 minutes (P = .05, after Bonferroni correction), as well as the area under the curve at 120 minutes (P = .036, after Bonferroni correction). Similarly, there was a significant increase following the consumption of rice pudding with 3 g of cinnamon in the GLP-1 response (P = .0082, after Bonferroni correction) and the change in the maximum concentration (P = .0138, after Bonferroni correction). However, there was no significant difference in GER, satiety, glucose, GIP, or the ghrelin response following the ingestion of the rice pudding with 3 g, 1 g, or no cinnamon.

"Cinnamon has been shown to be one of the most effective [herbs and medicinal plants] at regulating blood glucose," explain Dr. Hlebowicz and colleagues. "Our finding that cinnamon decreases the insulin demand, despite the lack of change in blood glucose concentrations, was probably due to enhanced glucose uptake via stimulation of the insulin receptor. This finding is consistent with the results of previous studies."

Furthermore, in this study, there appeared to be a relationship between the amount of cinnamon consumed, the reduction ininsulin concentration, and the delay in gastric emptying. "An intake of 3 g cinnamon reduced postprandial insulin concentrations more noticeably than did the ingestion of 1 g cinnamon, without affecting postprandial blood glucose or GER," point out the researchers.

One potential limitation of the study is the fact that glucagon concentrations after eating were not evaluated. Glucagon is a hormone secreted by the pancreas that stimulates increases in the concentration of blood glucose.

The authors conclude that cinnamon could be an important dietary supplement for those with poorly controlled diabetes. "The ability of cinnamon to control blood glucose concentrations in patients with type 1 and type 2 diabetes has not yet been fully evaluated," Dr. Hlebowicz and colleagues write. "Clearly, a long-term clinical trial involving a...[large] number of diabetes patients is needed to evaluate the effects of cinnamon supplementation in type 2 diabetes."

This study was supported by the Stig and Ragna Gothon's Foundation for Medical Research. The authors have disclosed no relevant financial relationships.

Am J Clin Nutr. 2009;89:815–821.


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