The new study, published in the European Journal of Clinical Investigation (Vol. 36, pp. 340-344), adds to a growing body of science linking the common spice to improvements in blood glucose levels in diabetics.
A previous study reported in 2003 (Diabetes Care, Vol. 26, pp. 3215-3218) that just 1g of the spice per day reduced blood glucose levels, as well as triglycerides, LDL cholesterol, and total cholesterol in a small group of people with type 2 diabetes.
But the researchers, from the University of Hannover, claim that their study is the first to evaluate an aqueous cinnamon extract on fasting glucose levels, serum lipid levels and glycated hemoglobin A1c (HbA1c) levels, in Western type-2 diabetics.
An estimated 19m people are affected by diabetes in the EU 25, equal to four per cent of the total population. This figure is projected to increase to 26m by 2030.
In the US there are over 20m people with diabetes, equal to seven per cent of the population. The total costs are thought to be as much as $132bn, with $92bn being direct costs from medication, according to 2002 American Diabetes Association figures.
In the new study, 79 diabetic volunteers were randomly assigned to receive either three capsules per day, each containing 112mg of aqueous cinnamon extract (by Finzelberg), equal to one gram of cinnamon, or an identical-looking placebo. Both active and placebo capsules per donated by Truw Arzneimittel Vertriebs GmbH.
The average age of the volunteers was 63, with average body mass index (BMI) of 29 to 30 kg per square metre. The volunteers were not receiving insulin therapy, but were controlling their disease by oral antidiabetics or diet.
After four months, the researchers found that fasting glucose levels improved by 10.3 per cent for the group supplemented with the cinnamon extract. No significant difference was observed in the placebo group.
"The positive correlation between baseline plasma glucose and the decrease of plasma glucose in our study… suggest that subjects with poor glycaemic control may benefit more from cinnamon intake," wrote lead author B Mang.
In contrast to other studies, no improvements in serum lipid levels were observed in this study. Previous studies have indicated that improved glycaemic control could lead to improvements in lipid profiles. Such an effect was not observed in this study, say the researchers, because the improvements in glucose concentrations were not sufficient to induce such a change.
Although the researchers could not identify why other studies reported greater blood glucose improvements, or improvements in blood lipid levels, they did say that this was most probably not due to using an aqueous extract since the active substances are suggested to be present in the aqueous extract: the methylhydroxychalcone polymer has been touted as the active substance.
"Using an aqueous extract of cinnamon, which is nearly free of lipophilic substances, may be safer than the powder because Cinnamomi cassiae cortex is known to cause allergic reactions owing to components of the volatile oil," said Mang.
"Our study shows that in Western type-2 diabetics treated in accordance with current guidelines, the intake of an aqueous cinnamon extract leads to a moderate effect on fasting plasma glucose," concluded the researchers.
The spice has also been linked to other health benefits, including Alzheimer's and cardiovascular disease (CVD).