Cinnamon

When moving from the study of molecular mechanisms to concrete clinical effects, cinnamon emerges as one of the most studied spices in humans, with a growing number of clinical trials, systematic reviews, and meta-analysis evaluating its impact on metabolism, the cardiovascular system, and glycemic control. This transition is fundamental, as it allows us to understand whether what happens at the cellular level truly translates into measurable real-life benefits.

One of the most investigated areas is that of blood pressure and lipid profile. In a randomized, double-blind, placebo-controlled clinical trial conducted on subjects with stage 1 hypertension, supplementation with 1500 mg of cinnamon per day for 90 days resulted in a significant reduction in 24-hour mean systolic blood pressure and daytime systolic blood pressure, accompanied by an improvement in the lipid profile, with an increase in HDL and a reduction in LDL (Shirzad et al., 2021) [6]. It is interesting to note that the effect on fasting glycemia was not marked in this context, suggesting that in non-diabetic subjects, the action of cinnamon manifests primarily on the vascular and lipid side, as if it were improving the "quality of the pipes" rather than intervening directly on the fuel flowing through them.

The picture becomes even clearer when looking at data on subjects with type 2 diabetes, a condition in which the alteration of glucose metabolism is central. A systematic review with meta-analysis that included 28 randomized clinical trials, for a total of over 3000 participants, showed that cinnamon supplementation significantly reduces fasting glycemia, post-prandial glycemia, HbA1c, and HOMA-IR, indicating a real improvement in insulin sensitivity (de Moura et al., 2025) [7]. In particular, the reduction of HOMA-IR (an index used to estimate insulin resistance and pancreatic β-cell function) suggests that cinnamon does not act simply by "buffering" glycemia, but intervenes further upstream, improving the dialogue between insulin and cells. It is as if insulin no longer has to shout to be heard, being able to return to performing its role with lower and more efficient signals.

A particularly relevant aspect that emerged from this meta-analysis concerns the dose: the most consistent effects on HbA1c (glycated hemoglobin, a blood test that indicates the average glycemia over the last 2-3 months), HOMA-IR, and even body mass index were observed with doses equal to or less than 2 grams per day, suggesting that, even for cinnamon, "more" does not necessarily mean "better" (de Moura et al., 2025) [7]. This is a key point in terms of conscious supplementation that is consistent with one's lifestyle.

Similar results also emerge in specific endocrine-metabolic contexts such as polycystic ovary syndrome (PCOS), a condition characterized by insulin resistance, dyslipidemia, and increased cardiovascular risk. In a systematic review and meta-analysis of randomized clinical trials, cinnamon supplementation led to a significant reduction in body weight, fasting glycemia, and HOMA-IR, along with an improvement in the lipid profile, with a reduction in total cholesterol and LDL (Xiaomei and Xiaoyan, 2024) [8]. In this context, cinnamon seems to act as a "transversal" metabolic modulator, capable of simultaneously influencing glycemia, lipids, and body weight—elements that in PCOS reinforce each other in a vicious cycle.

If we broaden our view to metabolic diseases in general, a dose-response meta-analysis that included 35 clinical trials confirmed that cinnamon supplementation reduces glycemia, serum insulin, total cholesterol, LDL, triglycerides, and waist circumference, while improving HDL and leading to a reduction, albeit modest but significant, in both systolic and diastolic blood pressure (Kutbi et al., 2022) [9]. The data on serum insulin is particularly interesting because it suggests that cinnamon may help reduce chronic hyperinsulinemia, one of the first pathological adaptations of modern metabolism. In other words, cinnamon does not just correct the consequences, but intervenes in one of the mechanisms that precede and fuel metabolic dysfunction.

These observations have been further reinforced by a recent systematic review with meta-analysis and GRADE assessment (a method used to evaluate the quality of available evidence and, for guidelines, the strength of recommendations), which included 49 randomized clinical trials and confirmed significant improvements in glycemia, HbA1c, HOMA-IR, lipid profile, blood pressure, and inflammatory markers such as CRP (Jafari et al., 2025) [10]. The reduction of oxidative stress markers, such as malondialdehyde, also suggests that part of the cardiovascular benefits may derive from an improvement in endothelial function, making vessels more "elastic" and less vulnerable to chronic inflammatory damage.

Taken together, these clinical data outline a coherent picture: cinnamon, when integrated appropriately, acts as a nutraceutical adjuvant capable of improving glycemic control, reducing hyperinsulinemia and insulin resistance, optimizing the lipid profile, and supporting cardiovascular health. However, it is clear that these effects are neither magical nor independent of the context. Cinnamon does not "cure" metabolic diseases on its own, but functions as a positive amplifier of a lifestyle already oriented toward glycemic stability, the reduction of insulin spikes, and the control of chronic inflammation.

In this sense, cinnamon represents an emblematic example of how a traditional spice can interact with the metabolic pathways of our body, offering concrete and measurable support, provided it is inserted within a coherent approach that takes into account overall nutrition, movement, and daily biological rhythm.

When observing the effects of cinnamon beyond glucose and cardiovascular metabolism, an even broader picture emerges, involving the nervous system, the endocrine system, systemic inflammation, and even processes related to cell proliferation. This reinforces the idea that cinnamon does not act as a “specific” remedy for a single pathology, but as a transversal modulator of multiple biological pathways, all characterized by chronic inflammation, oxidative stress, and metabolic dysfunction.

A first area of great interest is cognitive function. A systematic review that analyzed over 2,600 studies, selecting 40 from in vivo models, in vitro models, and clinical trials, showed that cinnamon and its main bioactive compounds, including cinnamaldehyde, eugenol, and cinnamic acid, are able to improve memory, learning, and synaptic plasticity in most of the experimental models analyzed. In animal models, the administration of cinnamon was associated with an increase in neurotransmitters involved in memory, such as acetylcholine, and a reduction in cerebral oxidative stress. In in vitro studies, cinnamon showed the ability to reduce the aggregation of pathological proteins such as β-amyloid and tau, which are key processes in neurodegenerative diseases. Although clinical evidence is still limited, these results suggest that cinnamon may act as a sort of “metabolic shield” for the brain, reducing inflammation and improving the efficiency of nerve cells, especially in contexts of aging or chronic metabolic stress (Nakhaee et al., 2024) [11].

Another field in which cinnamon shows relevant effects is oncology, thanks mainly to cinnamaldehyde. An in-depth review highlighted how this molecule is able to modulate numerous processes involved in tumorigenesis, including cell proliferation, apoptosis, angiogenesis, and tumor invasiveness. In particular, cinnamaldehyde interferes with the PI3K/AKT/mTOR signaling pathway, promotes cell cycle arrest, and activates programmed cell death in tumor cells. An interesting aspect is its ability to act in synergy with chemotherapy drugs, enhancing their efficacy and reducing their systemic toxicity. However, the same review points out that the oral bioavailability of cinnamaldehyde is limited and that much of current research is oriented toward the development of advanced formulations, such as nanoparticles and liposomes, to improve its absorption and tissue targeting (Han et al., 2024) [12]. This data is important because it reiterates a key concept: cinnamon is not a “natural anti-tumor drug,” but a bioactive molecule with modulating potential that can complement broader therapeutic strategies.

Returning to metabolism, a randomized clinical trial conducted on patients with poorly controlled type 2 diabetes showed that the intake of 1 g per day of cinnamon for 12 weeks significantly reduces fasting glycemia and improves markers of oxidative stress, such as the increase in glutathione and superoxide dismutase and the reduction of malondialdehyde (Sahib, 2016) [13]. Although the reduction in HbA1c did not reach statistical significance, the observed trend suggests that cinnamon contributes to improving the overall metabolic and oxidative environment. It is as if cinnamon acts by lowering the metabolic “background noise,” making the system more stable and less exposed to chronic damage.

A less known but particularly interesting area is that of headaches and migraines, conditions in which neurovascular inflammation plays a central role. In a randomized, double-blind study, supplementation with 1,800 mg per day of cinnamon for 8 weeks resulted in a significant reduction in the frequency, severity, and duration of migraine attacks, accompanied by a decrease in serum levels of IL-6 and nitric oxide (Zareie et al., 2020) [14]. These results suggest that cinnamon can modulate the inflammatory and vasodilatory mechanisms involved in the genesis of migraine pain. In practical terms, cinnamon seems to act more “upstream,” reducing the systemic inflammation that predisposes to the attack, rather than extinguishing the symptom once it has appeared.

Finally, an emerging line of research concerns the role of cinnamaldehyde in female endocrine-metabolic pathologies, such as polycystic ovary syndrome (PCOS). In an animal model of letrozole-induced PCOS, cinnamaldehyde showed significant effects in reducing body weight, hyperandrogenism, dyslipidemia, and glycemic alterations, while improving ovarian morphology (Siddiqua et al., 2026) [15]. At the molecular level, these benefits were associated with the suppression of inflammation and the reduction of cytokines such as IL-1β and IL-18, along with an enhancement of antioxidant defenses. It is particularly interesting that molecular docking analysis showed a direct interaction of cinnamaldehyde with these targets, suggesting a consistent and biologically plausible mechanism of action.

Taken together, this evidence shows how cinnamon and its bioactive components can be used as tools for physiological modulation in numerous pathological contexts, all characterized by chronic inflammation, oxidative stress, and metabolic dysfunction. Once again, the key message is that cinnamon does not replace pharmacological therapies nor does it act in isolation, but finds its maximum efficacy when it is included within a lifestyle oriented toward metabolic stability, the reduction of hyperinsulinemia, and the control of low-grade inflammation. It is in this context that an ancient spice manages to engage with the most modern problems of human health, offering measurable, consistent, and scientifically grounded support.

Among all the metabolic effects attributed to cinnamon, the one related to the improvement of insulin resistance is likely the most clinically relevant. This aspect is of central importance considering that insulin resistance is one of the main pathophysiological mechanisms underlying type 2 diabetes, visceral obesity, fatty liver disease, metabolic syndrome, and polycystic ovary syndrome. In these conditions, the problem concerns not only increased glycemia, but above all the progressive inability of peripheral tissues to respond correctly to insulin signaling. The pancreas is therefore forced to produce increasing amounts of insulin in an attempt to keep glycemia stable, establishing a state of chronic hyperinsulinemia that promotes inflammation, lipid accumulation, and continuous activation of the PI3K/AKT/mTOR pathway.

In this context, cinnamon appears to exert an extremely interesting action, as it does not act solely by lowering glycemia, but by directly improving the cellular response to insulin. Recent experimental studies have shown that cinnamaldehyde, the main bioactive compound in cinnamon, significantly improves insulin sensitivity in insulin-sensitive peripheral tissues, increasing glucose uptake in skeletal muscle and adipose tissue while simultaneously promoting hepatic glycogen accumulation (Frederico et al., 2025) [16]. The study also highlighted that these effects depend on the activation of a receptor and the involvement of intracellular pathways closely linked to insulin signaling, including PI3K and MAPK (a family of protein kinases fundamental in eukaryotic cells).

The activation of these pathways promotes the translocation of the GLUT4 transporter toward the cell membrane, allowing for more effective glucose entry into the cell. It is as if cinnamon helps peripheral tissues "regain sensitivity" after prolonged exposure to high levels of insulin. Also particularly interesting is the role of intracellular calcium and the cytoskeleton in the response to cinnamaldehyde, suggesting that the compound influences not only metabolic signals but also the structural mechanisms necessary for the correct intracellular trafficking of vesicles containing GLUT4.

These molecular effects are also concretely confirmed by clinical data. A vast systematic review with meta-analysis including 28 randomized controlled trials and over 3000 patients with type 2 diabetes has shown that cinnamon supplementation leads to a significant reduction in fasting glycemia, postprandial glycemia, HbA1c, and the HOMA-IR index (de Moura et al., 2025) [7]. The reduction in HOMA-IR is particularly important because it represents one of the main indirect indicators of systemic insulin resistance. In other words, the data suggest that cinnamon does not only improve "superficial" glycemic control, but acts directly on the metabolic defect underlying type 2 diabetes.

A very interesting aspect that emerged from the meta-analysis also concerns the dosage. The most evident benefits were observed with moderate doses, less than or equal to 2 grams per day, suggesting that cinnamon acts more as a physiological modulator of metabolism than as a simple dose-dependent pharmacological agent (de Moura et al., 2025) [7]. This concept is consistent with the nutraceutical role of the spice: not a substance that artificially "forces" metabolism, but a compound capable of gradually rebalancing pathways altered by chronic energy excess.

Similar results were also observed in women affected by polycystic ovary syndrome (PCOS), a condition closely associated with hyperinsulinemia and insulin resistance. A meta-analysis of randomized clinical trials showed that cinnamon supplementation significantly improves the HOMA-IR index, reduces fasting glycemia, and improves the lipid profile in patients with PCOS (Xiaomei and Xiaoyan, 2024) [8]. This finding is particularly relevant because in PCOS, insulin does not act only as a metabolic hormone, but contributes directly to androgenic ovarian stimulation, promoting ovulatory dysfunction and endocrine alterations. Improving insulin resistance therefore means intervening in one of the central mechanisms of the pathology.

Even the most recent general reviews of meta-analyses confirm this picture. An umbrella review including 21 meta-analyses concluded that cinnamon significantly improves fasting glycemia, various lipid parameters, and numerous processes associated with insulin resistance and oxidative stress, especially in subjects with diabetes mellitus and metabolic syndrome (Gou et al., 2025) [17]. The authors also emphasize that the bioactive compounds in cinnamon appear to increase the expression of the insulin receptor β and the GLUT4 transporter, reduce hepatic gluconeogenesis, and favorably modulate lipid metabolism. All these effects converge toward a common goal: reducing the metabolic load imposed on insulin and improving energy flexibility.

Overall, the available evidence shows that cinnamon does not act through a single isolated target, but through a coordinated regulation of multiple pathways involved in insulin sensitivity, glucose metabolism, and cellular energy management. By improving glucose uptake, reducing compensatory hyperinsulinemia, modulating lipid metabolism, and attenuating oxidative stress, cinnamon appears to contribute to breaking one of the main vicious cycles of modern metabolic diseases. In this sense, the relationship between cinnamon and insulin resistance represents one of the most interesting examples of how a traditional spice can interact with the deepest mechanisms of metabolic physiology, offering biologically coherent support for the prevention and management of conditions characterized by chronic hyperinsulinemia and cellular energy dysfunction.

One of the most interesting and, at the same time, least intuitive aspects of cinnamon emerges when observing its impact on intracellular mechanisms of cell growth and survival, particularly on the PI3K–AKT–mTOR axis, one of the body's main metabolic and proliferative hubs. This pathway, as we have already analyzed extensively in chapter 4, is responsible for translating nutritional and hormonal signals into growth, protein synthesis, and cell survival, but it becomes pathological when it is chronically hyperactivated, as occurs in conditions of hyperinsulinemia, chronic inflammation, and the tumor microenvironment.

Cinnamaldehyde, the main bioactive compound in cinnamon, has proven capable of interfering with this axis in a selective and consistent manner, reducing the proliferative activity of cells and promoting processes of apoptosis and autophagy. In colorectal carcinoma models, for example, it has been shown that cinnamaldehyde causes a marked inhibition of the PI3K/AKT/mTOR pathway, resulting in the activation of apoptosis and a reduction in tumor proliferation (Zhang et al., 2024) [18]. It is as if cinnamaldehyde strikes a “structural pivot” of the cell, rendering the entire growth machinery that revolves around mTOR inefficient.

A similar mechanism has been observed in ovarian carcinoma, where cinnamaldehyde has shown the ability to block the epithelial-mesenchymal transition (EMT), a fundamental process for tumor invasiveness and metastasis. In this context, the molecule acts by inhibiting the phosphorylation of PI3K, AKT, and mTOR, even in the presence of strong proliferative stimuli such as EGF (epidermal growth factor). The result is a reduction in invasion, cell migration, and metastasis formation, both in vitro and in vivo (Wang et al., 2022) [19]. From a biological standpoint, this means that cinnamaldehyde is able to “silence” the growth signal even when the cell receives strong external inputs, demonstrating an action upstream of the pathway.

The link between cinnamaldehyde, mTOR, and the hypoxic response becomes even more evident in studies on glioma, one of the most aggressive and metabolically adaptable neoplasms. In this model, cinnamaldehyde has been shown to reduce the expression of HIF-1α, the main transcription factor activated by mTOR, which allows tumor cells to survive in hypoxic conditions. This effect does not occur by increasing the degradation of HIF-1α, but by reducing its protein synthesis, a process directly controlled by mTOR: the down-regulation of HIF-1α is in fact mediated by the inhibition of the PI3K/AKT/mTOR pathway (Wang et al., 2022) [20]. In other words, cinnamaldehyde turns off the tumor cell's “adaptation program” to hypoxia, making it more vulnerable and less invasive.

This ability to interfere with the hypoxic response has also been confirmed in sarcoma and melanoma models, where cinnamaldehyde reduced angiogenesis (the natural process of forming new blood vessels, or capillaries, from pre-existing vessels) and metastasis by inhibiting the synthesis of HIF-1α through the suppression of the PI3K/AKT/mTOR pathway. The reduction of HIF-1α leads to a lowering of the expression of key molecules involved in angiogenesis and EMT factors, with a clear slowing of tumor progression (Patra et al., 2019) [21]. It is important to emphasize that this mechanism is also particularly relevant outside of oncology, because HIF-1α and mTOR are involved in pathological states linked to hyperinsulinemia, chronic inflammation, and immune system dysfunction.

Confirming the central role of mTOR, studies conducted on oral carcinoma have shown that both Cinnamomum zeylanicum extract and pure cinnamaldehyde induce apoptosis, cell cycle arrest, and autophagy through the coordinated inhibition of the PI3K/AKT/mTOR pathway. In this context, the activation of autophagy appears as an “orderly” adaptive response, which allows the cell to enter a controlled shutdown program rather than chaotic proliferation (Aggarwal et al., 2022) [22]. This is a conceptually very important point, because mTOR represents one of the main brakes on autophagy: its inhibition by cinnamaldehyde therefore reopens one of the main channels of cellular maintenance. Taken together, these studies clearly show that cinnamon, through cinnamaldehyde, does not act in a non-specific way, but strikes strategic nodes of cell signaling. The inhibition of PI3K, AKT, and mTOR, the reduction of HIF-1α synthesis, and the reactivation of autophagy outline a profile of action consistent with that of a metabolic and proliferative modulator, capable of countering the effects of insulin hyperactivation and disordered growth.

This data integrates perfectly with what was seen in the previous chapters: in a lifestyle context characterized by chronic hyperinsulinemia, mTOR remains constantly switched on, promoting inflammation, immune system dysfunction, and loss of proliferative control. Cinnamon, on the contrary, acts as an opposing signal, bringing the system back toward a more parsimonious, efficient, and reparative mode. It does not “turn off” growth in a toxic way, but scales it back, allowing the cell to return to distinguishing between when to grow and when to stop.

In this sense, the relationship between cinnamon and mTOR represents one of the clearest examples of how a traditional spice can interact with the insulin pathway, offering rational and scientifically grounded support for the management of metabolic, immune, and proliferative pathologies.

While the previous paragraphs observed how cinnamaldehyde is capable of directly reducing the proliferative activity linked to the PI3K/AKT/mTOR axis, there is a second, even more interesting level of regulation: that exerted through AMPK, a fundamental enzyme that acts as the primary energy sensor of our cells. To understand the importance of this mechanism, it is necessary to remember that mTOR and AMPK represent, biologically, two opposing metabolic programs. When energy is abundant, insulin is high, and nutrients are constantly available, mTOR promotes growth, protein synthesis, and energy storage. Conversely, when the cell senses a reduction in available energy, AMPK comes into play, slowing down anabolic processes, promoting the oxidation of energy substrates, and reactivating autophagy. In other words, AMPK functions as a “metabolic survival switch,” while mTOR represents the “expansion program.”

It is precisely in this context that cinnamon demonstrates one of its most biologically consistent effects. Several studies have indeed highlighted that its main bioactive compounds, particularly cinnamaldehyde and trans-cinnamic acid, do not merely inhibit mTOR indirectly, but significantly activate AMPK, shifting the cell toward a more conservative and efficient metabolic mode. In mouse adipocytes, for example, cinnamaldehyde significantly increased AMPK phosphorylation, while simultaneously reducing the expression of the main regulators of lipogenesis (the biochemical process through which the body synthesizes fatty acids and combines them to form triglycerides) and adipocyte maturation. This effect was attenuated by the use of Compound C, a pharmacological inhibitor of AMPK, confirming that the activation of this pathway represents one of the central mechanisms through which cinnamon exerts its metabolic effects (Huang et al., 2011) [23]. In practical terms, cinnamaldehyde seems to “convince” the cell that energy should be used more sparingly, thereby blocking the lipid accumulation programs supported by mTOR.

This concept becomes even more evident in studies on hepatic steatosis associated with a high-fat diet. In cellular and animal models subject to steatotic liver disease, trans-cinnamic acid has shown the ability to bind directly to the AMPKα1 catalytic subunit, promoting its activation and modulating the AMPK-mTOR axis in a coordinated manner. This is an extremely relevant finding, because many natural compounds activate AMPK indirectly, whereas in this case, the compound derived from cinnamon appears to interact directly with the kinase domain of the enzyme, stabilizing its activity. The final effect is a reduction in hepatic lipogenesis, an increase in fatty acid oxidation, and, above all, a reactivation of lipophagy, i.e., the autophagic degradation of intracellular lipid droplets (Jia et al., 2026) [24]. From a physiological point of view, this means that the liver cell progressively stops accumulating fat and begins to “consume” it again.

The most interesting aspect, however, concerns the dynamic relationship between AMPK and mTOR. When AMPK is activated, one of its main effects is precisely the inhibition of mTORC1. This allows the cell to reduce synthesis processes and reopen the autophagic programs that mTOR tends to suppress. In other words, cinnamon does not act simply by “turning off” mTOR, but by reactivating the natural physiological antagonist of this pathway. It is a very different mechanism compared to that of direct pharmacological inhibition: the regulation occurs adaptively, as a response to an improvement in the cellular energy balance.

Further confirmation comes from studies on cinnamon extract in adipocytes and myocytes, where an increase in AMPK phosphorylation was observed, accompanied by an increase in GLUT4 translocation and cellular glucose uptake (Shen et al., 2014) [25]. An extremely interesting finding emerges from this study: insulin, especially when present chronically, appears to exert an antagonistic effect on AMPK activation in adipocytes. This means that conditions of persistent hyperinsulinemia physiologically tend to keep AMPK “off,” leaving mTOR constantly active. Cinnamon, conversely, seems to interrupt this imbalance, reactivating AMPK even in a metabolically compromised environment.

An additional piece of the puzzle is added by studies on trans-cinnamic acid and adiponectin. In mouse adipocytes, the compound significantly increased adiponectin secretion and the pAMPK (AMPK phosphorylation) /AMPK ratio (Kopp et al., 2014) [26]. This step is particularly important because adiponectin represents one of the most potent insulin-sensitizing molecules produced by adipose tissue. The increase in adiponectin leads to greater fatty acid oxidation, a reduction in lipogenesis, and an improvement in systemic insulin sensitivity—all effects closely associated with AMPK activation and the reduction of mTOR activity.

Overall, these data show that cinnamon does not act on a single isolated target, but rebalances an entire metabolic axis. The activation of AMPK, the functional inhibition of mTOR, the reactivation of autophagy, the reduction of lipogenesis, and the improvement of glucose metabolism delineate a biological profile that is extraordinarily consistent with the metabolic needs of the modern organism, which is increasingly characterized by chronic energy excess, persistent hyperinsulinemia, and pathological lipid accumulation.

In this sense, the relationship between cinnamon, AMPK, and mTOR likely represents one of the most fascinating examples of how a natural substance traditionally used throughout the history of nutrition can interact with the most sophisticated cellular energy regulation mechanisms, helping to restore metabolism toward a condition of greater flexibility, efficiency, and control.