If we had to name one spice that defines winter it would be, beyond any doubt, cinnamon. From delicious cookies to mulled wine, from spiced latte to scented candles, this spice is ubiquitous during the cold season. But neuroscience has taken a particular interest in this beloved spice for a slightly different reason: its apparent protection against neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease.
Alzheimer’s disease is characterized by abnormal aggregates of two proteins: amyloid beta and tau, which lead to the death of neurons (for a more detailed explanation, see this article), with the most well-known symptom being progressive memory loss. Parkinson’s disease is a movement disorder best recognized by its characteristic tremor and is caused by degeneration (i.e. death) of dopamine-producing neurons. Furthermore, similar to Alzheimer’s disease, the brains of Parkinson’s patients display abnormal deposits of a type of protein called α-synuclein. As we all know, there is currently no cure for any of these disorders, although some treatments might, at least temporarily, alleviate the symptoms.
In both of these disorders, however, research efforts have been focused on preventing neuronal degeneration, either by destroying the protein aggregates (in both Alzheimer’s and Parkinson’s disease) or by boosting proteins which prevent this type of degeneration (in Parkinson’s disease). As part of these efforts, scientists have looked at the effect of cinnamon extract against such types of degeneration.
The first studies were conducted in vitro (that is, on isolated cells) and checked whether cinnamon extract is capable of preventing the aggregation of the three proteins mentioned before (i.e., amyloid beta, tau, and α-synuclein). The results were positive, i.e. the administered cinnamon extract was successful in disrupting the formation of clumps of these proteins.
Based on this evidence, researchers could move on to the next step and test the effects of cinnamon in vivo, in animal models. There are two obvious challenges when it comes to formulating a hypothesis about how substances will behave in vivo compared to in vitro, and they are not specific to cinnamon extract only. On the one hand, when you ingest something, your digestive system breaks that down for you, so what you eat might not resemble what gets absorbed in your blood. On the other hand, because your brain is so important, it has an extra layer of protection compared to other organs, namely the blood-brain barrier. This layer is actually impermeable to most molecules and is what makes drug delivery into the brain so challenging. In short, it means that, even though a treatment is wildly successful in vitro, it might not even make it into the brain in vivo.
Nevertheless, studies conducted on mice models who were fed cinnamon extract showed ameliorated symptoms both for Alzheimer’s and Parkinson’s disease in these mice. At the same time, analysis of their brains revealed decreased neuronal degeneration, suggesting that cinnamon does have some potential as a treatment for these debilitating disorders.
But does that mean that you should go on an exclusive cinnamon diet to protect yourself against developing Alzheimer’s or Parkinson’s disease? No, definitely not. For one, these results have not yet been replicated in humans, and just because they work for our rodent friends, it doesn’t mean they also work for us. Secondly, although scientists have some idea regarding the actual beneficial compounds in cinnamon, as well as about their molecular mechanisms of action, more research is still necessary before we have a complete understanding of their mode of work and of any potential side effects. At the same time, cinnamon does show some promise as a treatment, and it’s nice to think that this beloved spice could help in that regard.
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