Cinnamon is a spice commonly available as a dried powder. Cinnamon powder is derived from the botanical herb Cinnamomum verum and Cinnamonum zeylancium. The spice has a traditional use as a flavouring agent, as well as a health remedy. A number of health effects have been reported following cinnamon consumption, and these may relate to its high antioxidant content. In particular, cinnamon has a reputation as being valuable in the treatment of blood sugar disorders such as diabetes, obesity and metabolic syndrome, suggesting that it may have blood sugar lowering effects. Compounds within the cinnamon dried herb and its whole food form possess insulin mimicking effects, which have been reported to be much higher than other herbs and spices that have been tested (perhaps as high as 20-fold). Cinnamon appears to improve insulin sensitivity through an increased expression of GLUT 4 transporters, and this lowers fasting blood glucose levels, which in turn results in a lowering of fasting insulin levels.
The insulin sensitising effects of cinnamon likely result from the aqueous fraction left following removal of the oil. Components of the oil including cinnamaldehyde, cinnamic acid, eugenol and coumarin have no insulin sensitising effects when tested. Further the insulin sensitising effects of cinnamon are present in the whole herb before removal of the oil and following separation of the lipid and aqueous fractions activity remains only in the aqueous fraction. Interestingly, the water fraction of cinnamon contains polyphenols compounds that are trimer and tetramers of catechin and epicatechin, the same compounds that are present in green tea. These compounds are thought to be responsible for some of the health benefits conferred to tea drinkers. Catechins and epicatechin belong to the flavan-3-ols group of flavonoids and their presence in green tea, and black tea to a lesser extent, may explain the insulin sensitising effects seen in tea drinkers. Cocoa powder also has insulin sensitising effects and contains similar flavon-3-ol compounds.
Rats that have consumed cinnamon have been shown to have higher glucose infusion rates compared to control rats. This suggests that cinnamon significantly increases glucose disposal. Cinnamon also increases the expression of insulin-stimulated insulin receptor substrate 1 (IRS-1), increased cellular levels of tyrosine phosphorylation and levels of IRS-1/phosphoinositide 3-kinase (PI3K) in the skeletal muscle of rats. Cinnamon therefore likely improves insulin signalling in skeletal muscle. Rats fed high fructose diets are protected from the normal fructose induced insulin resistance that accompany high fructose diets, when they are concomitantly fed cinnamon. These results from rats are supported by similar studies in humans, suggesting that cinnamon may have similar insulin sensitising effects in all mammals. The ability of cinnamon to improve insulin signalling may derive from an antioxidant effect, but its superior effects to other herbs suggest that other mechanism are also responsible at least in part.
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