Insulin resistance is considered a major metabolic change associated with the development of the metabolic syndrome, which can increase the risk of developing diabetes and cardiovascular disease. Insulin resistance is caused by a down regulation of the cellular insulin cascade, possibly via increased oxidative stress, which may alter the translocation of glucose receptors to the membrane. A number of nutrient factors have been identified for their insulin receptor sensitising effect, and are perhaps beneficial at preventing or reversing insulin resistance because they are able to inhibit the oxidative stress that damages the insulin cascade. One such agent is cinnamon, a spice known to contain high concentrations of polyphenol antioxidants. In animal models, cinnamon has proved effective at increasing glucose uptake through improved insulin signalling. Nutritional researchers are therefore interested in the effects of cinnamon on human glucose metabolism and insulin function.
To investigate the beneficial effects of cinnamon on antioxidant status researchers1 used a double blind placebo controlled study involving 22 insulin resistant subjects with body mass indexes between 25 to 45kg/m2. Subjects received capsules containing either 250mg of aqueous extract of cinnamon two times per day for 12 weeks or a placebo. The results showed that the Ferric Reducing Activity of Plasma and thiol groups (SH) increased, while malonaldehyde plasma levels decreased, indicative of decreased systemic oxidative stress. This effect was greater at 12 weeks compared to 6 weeks suggesting that the benefits were slow to accumulate. The researchers also reported a positive correlation between malonaldehyde plasma levels and plasma glucose levels, with impaired plasma glucose levels returning to normal physiological levels after 12 weeks. Cinnamon may therefore be an effective therapeutic treatment for insulin resistance in humans, as shown previously in animal models.