Cinnamon: scientific evidence, mechanisms of action, and applications for human health

Cinnamon is often cited as a functional spice, meaning a spice that, in addition to flavor, also provides biologically active compounds. This definition helps to understand its real positioning in modern nutrition. A functional spice is not a drug and does not promise universal effects; rather, it is an ingredient that, in addition to taste, brings with it a density of molecules potentially relevant to the body. In the case of cinnamon, its interest lies in practical use: it can add character to simple preparations, facilitate the reduction of added sugars, and improve adherence to a more moderate eating pattern. Available reviews and meta-analyses, which are studies that synthesize the results of multiple research, describe favorable signals, especially in metabolic parameters, but always within the context of a diet already oriented towards quality and a consistent lifestyle [8,9,10].

From a clinical perspective, the most important aspect is to avoid overinterpretation. Cinnamon does not "compensate" for a disordered diet, does not replace physical activity, and does not substitute for any therapies. However, it can be usefully integrated into a routine, especially when the priority is to make a low-sugar meal more pleasant or to improve the acceptability of foods like yogurt, oats, fruit, or hot beverages. This is one of the reasons why the spice is often associated with cardiometabolic prevention strategies, i.e., the prevention of diseases involving the heart, blood vessels, and metabolism: it does not act on a single target, but is part of a broader dietary model. Reviews, which are critical syntheses of the literature, on the genus Cinnamomum emphasize that there are numerous bioactive compounds and that the composition can vary based on the species and form of consumption [8,4].

In practice, the nutritional value of cinnamon is twofold. On one hand, it offers an immediate sensory advantage, because it allows for flavor without resorting to large amounts of sugar. On the other hand, it provides a small amount of bioactive molecules that have attracted research attention regarding glycemia, inflammation, and lipid metabolism, i.e., how the body manages fats. Here, however, it is crucial to distinguish between powdered spice, extract, and supplement. Powder, in fact, is the most common form in cooking and the closest to traditional food use; extracts and supplements, on the other hand, are more concentrated and serve experimental or more precise supplementation objectives. Reviews dedicated to the pharmacological, i.e., related to the effects of substances on the body, and nutritional aspects of cinnamon highlight precisely this difference in context, because the meaning of a dose changes whether one refers to a teaspoon in cooking or a standardized extract in a study [8,3]. Understanding this point helps to better interpret cellular mechanisms, i.e., the processes that occur in cells, and clinical trials, i.e., studies conducted on people, where the form of intake significantly modifies the observed outcome. From here, we move on to explaining how cinnamon interacts with the main nodes of cellular metabolism.

• Helps reduce added sugars without losing palatability.
• Provides bioactive compounds studied for metabolism.
• Lends itself well to simple, fiber-rich foods.
• Shows different results according to form, dose, and context.

Cinnamon is biologically interesting because some of its constituents appear to interact with the cell's main energy control systems, i.e., the mechanisms that decide how to use and conserve available resources. Among the most studied targets are AMPK, mTOR, GLUT4, and AS160, which are elements that regulate energy availability, glucose trafficking, and the balance between cell growth and maintenance. AMPK, for example, is a kinase, an enzyme that modifies other proteins by adding phosphate groups, and is sensitive to energy status: when the cell perceives a reduction in available resources, this enzyme activates and directs metabolism towards a more efficient use of substrates. mTOR, on the contrary, is a signaling node that integrates nutrient and growth signals; when chronically active, it can promote anabolic processes that are not always useful in contexts of nutritional overload [6,7,14].

In the case of cinnamon, cinnamaldehyde is one of the most studied molecules. In cellular and animal models, it has been associated with increased AMPK activation and a reduction in adipocyte formation, i.e., cells specialized in fat storage. In a study on 3T3-L1 and mice fed a high-fat diet, cinnamaldehyde reduced lipid accumulation and attenuated several metabolic markers. The effects also included improvements in insulin resistance and lipid profile, while in the murine model it was used at a dose of 40 mg/kg [6]. This data is important because it shows a possible connection between AMPK modulation and the effects observed at the level of adipose tissue and systemic metabolism. Adipocyte biology, in fact, does not only concern energy storage, but also the secretion of mediators that influence inflammation, insulin sensitivity, and cardiometabolic risk. Reducing adipogenesis can therefore translate, at least experimentally, into a metabolic environment less favorable to insulin resistance. However, the rationale is not linear or universal: it depends on the model, dosage, and form of the compound. 2024 reviews on cinnamaldehyde confirm that mechanistic interest also concerns the regulation of proliferation, inflammation, and oxidative stress, but always within a heterogeneous experimental framework [5,11].

Another crucial step is the relationship between AMPK and mTOR. When AMPK is activated, it can help limit the mTORC1 signal, the mTOR complex most directly involved in protein synthesis and growth processes. This occurs through multiple transduction pathways, including those involving TSC1/TSC2, a regulatory complex that inhibits excessive mTOR activation. The biological consequence of this modulation is a better balance between cellular construction and recycling, with possible repercussions on autophagy, glucose and lipid metabolism, mitochondrial function, and oxidative stress. Autophagy, the process by which the cell recycles damaged components to maintain homeostasis, is not a simple "cleaning" mechanism, but a survival program. In this sense, AMPK activation and mTORC1 inhibition can promote a more adaptive phenotype, especially under conditions of nutritional excess or metabolic stress. This is the same conceptual axis observed in other natural compounds that improve insulin sensitivity via AMPK and mTOR inhibition, and this helps to understand why the topic is recurrent in nutritional literature [14,15,16].

The third fundamental node concerns glucose transport. GLUT4 is the transporter that allows muscle and adipose tissue to increase glucose uptake in response to insulin; AS160, on the other hand, is a regulator of the trafficking of vesicles containing GLUT4. When intracellular signals function well, GLUT4 moves to the cell membrane and facilitates glucose uptake. In conditions of insulin resistance, this step is compromised, and numerous classic studies have shown that the defect in GLUT4 translocation contributes to human insulin resistance [17,18,19]. In this context, cinnamon becomes interesting because some extracts have increased glucose uptake in adipocytes and myocytes through the LKB1-AMPK pathway, linking the energy signal to transporter trafficking [13]. From a pathophysiological point of view, this is relevant because chronic hyperglycemia does not only depend on reduced insulin secretion, but also on an inefficient peripheral response. Hence the biological plausibility of possible effects on glycemia and insulin sensitivity. The next step is therefore to observe how these mechanisms translate into the main physiological outcomes studied in humans.

• AMPK activation and improved cellular energy efficiency;
• mTORC1 modulation and autophagy processes;
• facilitation of glucose transport in peripheral tissues.

When moving from the cell to the organism, cinnamon shows its most interesting, but also most complex, profile. The spice has been evaluated primarily in relation to glycemia, insulin sensitivity, lipid metabolism, blood pressure, inflammation, and oxidative stress, which is the excess of reactive molecules that damage cells and tissues. The picture is not one of a unique and immediate effect, but rather of a possible modulation of multiple physiological systems. Validated meta-analyses and reviews suggest that cinnamon may offer support in metabolic disorders, especially when the initial condition is characterized by dysmetabolism and insulin resistance [9,20,21,10]. However, the significance of this support depends on the form used, the duration of the intervention, the dose, and the population studied. In pathophysiological terms, this hypothesis is plausible because metabolic disorders rarely involve only one biological axis: glucose, lipids, inflammation, and endothelial function, i.e., the activity of the inner lining of blood vessels, influence each other, and a nutraceutical can only act if it intercepts more than one of these nodes.

The most discussed data is glycemic, meaning related to the concentration of glucose in the blood. A review and meta-analysis on subjects with type 2 diabetes showed improvements in metabolic biomarkers, while a recent 2025 study confirmed a possible favorable effect on various indicators, albeit without absolute uniformity among trials [20]. In a randomized, placebo-controlled trial, meaning randomly assigned and compared with an inactive product, conducted in Iraqi patients with poorly controlled type 2 diabetes, cinnamon showed an antidiabetic and antioxidant effect, with an improvement in metabolic parameters compared to placebo [22]. In the Cochrane review dedicated to diabetes, the average dose was 2 g per day for periods between 4 and 16 weeks, with a prevalence of Cinnamomum cassia, confirming that much of the historical literature concerns cassia and not generic cinnamon [23]. This detail is important because the botanical species influences the final interpretation of the results. At a mechanistic level, the spice could influence peripheral glucose uptake, insulin signaling, and postprandial management, i.e., the trend after meals, with more visible effects when insulin resistance is already present.

The cardiovascular profile has also been extensively studied. A 2020 meta-analysis of 9 randomized trials, with 641 participants, observed significant reductions in both systolic and diastolic blood pressure, with a more evident effect when supplementation was equal to or less than 2 g per day and lasted more than 8 weeks; the reported average reductions were -5.17 mmHg for systolic and -3.36 mmHg for diastolic [24]. On the lipid side, meaning circulating fats in the blood, a specific meta-analysis highlighted modest and not always uniform effects on blood lipids, suggesting that the impact is real but contained [25]. This aligns well with the most recent mechanistic and clinical reviews, which describe cinnamon as a possible supportive nutraceutical for the cardiovascular system and for some metabolic complications [3,12,21]. In practice, the strongest signal seems to emerge in people with increased cardiometabolic risk, where even a small reduction in blood pressure or lipids can have a cumulative clinical significance. Therefore, the potential of the spice should be interpreted in the overall context, not as an isolated response of a single parameter.

Another relevant area is that of inflammation and oxidative stress. The 2020 meta-analysis on cardiometabolic indicators of inflammation and oxidation concluded that cinnamon supplementation can be an adjuvant, i.e., additional support, to reduce these markers in humans [26]. A randomized, double-blind, placebo-controlled trial on migraine attacks also showed a reduction in some inflammatory markers, confirming that cinnamon's potential is not limited to glucose metabolism [27]. On a pathophysiological level, this is consistent with the idea that compounds like cinnamaldehyde can interfere with intracellular signals, i.e., within cells, involved in cellular stress and the inflammatory response [2,5]. Overall, the data suggest a more evident supportive effect in contexts where metabolic or inflammatory alterations already exist. For this reason, cinnamon should be seen as an ingredient with possible functional utility, not as a standalone solution. From here, it becomes useful to observe which clinical conditions have been studied most often and where the signal is most convincing.

• Glycemia can be reduced, especially in contexts of impaired glucose control.
• Insulin sensitivity can improve in some subjects with insulin resistance.
• Blood lipids show modest and not always uniform variations.
• Inflammation and oxidative stress can be attenuated in a complementary way.

Cinnamon has been studied in numerous conditions, but the most robust core concerns metabolic disorders, i.e., alterations involving how the body manages energy, sugars, and fats. Type 2 diabetes, metabolic syndrome, and polycystic ovary syndrome are the three clinical scenarios where biological rationale and experimental observations converge with greater consistency. In all these cases, the same basic problems recur: altered glucose management (blood sugar), insulin resistance (a reduced tissue response to insulin), dyslipidemia (an alteration of circulating fats), and often low-grade chronic inflammation. It is here that cinnamon is interpreted as a possible nutritional support, not as an alternative to established treatments [9,20,28,30].

Type 2 diabetes is the most studied condition because it coincides with the pathways, i.e., the biological cell signaling pathways, that cinnamon seems to modulate best. A 2025 meta-analysis, a study that combines the results of multiple research projects, on metabolic biomarkers in patients with type 2 diabetes confirmed a real clinical interest, albeit with non-uniform effects across studies [20]. The 2012 Cochrane review already showed that available studies used oral cinnamon monopreparations, especially cassia, with an average dose of 2 g per day for 4-16 weeks, but the general conclusion remained cautious [23]. This indicates that the topic is old and still evolving, with signs of efficacy but not full therapeutic certainty. The same applies to metabolic syndrome, the set of multiple metabolic and cardiovascular alterations that tend to coexist, where cinnamon is studied as an additional intervention in a multifactorial context [9,10]. In pathophysiological terms, i.e., disease mechanisms, the spice is interesting because it acts on processes upstream of clinical damage: inefficient insulin signaling, excess hepatic glucose production, lipid accumulation, and oxidative stress, i.e., an excess of reactive molecules that damage cells and tissues. When these mechanisms combine, small improvements in insulin sensitivity or lipid profile can have clinical significance, especially when integrated into an already structured dietary and pharmacological strategy.

PCOS, or polycystic ovary syndrome, represents a particular case because it combines endocrine, i.e., hormonal, dysfunction and insulin resistance. Here, cinnamon has shown interesting results in several trials, i.e., controlled clinical studies: in a pilot study, 15 women with PCOS were randomized to daily oral cinnamon or placebo for 8 weeks, and the cinnamon group showed a significant reduction in insulin resistance [28]; in another randomized, double-blind trial, i.e., with random assignment and without participants and researchers knowing who received the treatment, 45 women received 1.5 g/d for 6 months, with favorable indications on some clinical aspects, including menstrual cyclicity [29]. A 2024 review and meta-analysis on women with PCOS further framed the spice's interest in cardiovascular risk markers, suggesting a possible complementary role [31]. These results are useful because they show internal consistency: when the underlying problem is insulin, cinnamon tends to show the most interesting signal. However, this is not a universal effect, and its interpretation must always be placed in the context of the patient's overall management [30,29]. From a clinical perspective, this means that cinnamon can accompany weight correction, diet, and physical activity, but it does not replace gynecological, endocrinological, and metabolic evaluation.

Emerging areas, such as neuroprotection and oncology, warrant a more cautious reading. The review on cognitive function describes preclinical data, i.e., obtained in the laboratory or on experimental models, and clinical data, but the evidence in humans remains limited compared to the metabolic area [32]. The rationale is plausible, because oxidative stress and inflammation also contribute to neuronal damage, but the available results do not yet allow for strong practical conclusions. In oncology, cinnamaldehyde, one of the main aromatic compounds of cinnamon, has been associated in experimental models with antiproliferative, apoptotic (capable of promoting programmed cell death), and signaling pathway modulation effects, but these observations do not allow for drawing clinical indications for practice [11,33,34,35,36,37]. The most accurate message is therefore hierarchical: strong interest in metabolic disorders, intermediate interest in some cardiovascular and inflammatory outcomes, and still an exploratory area for neuroprotection and experimental oncology. This distinction is essential to keep the interpretation aligned with the quality of the available evidence. In other words, cinnamon should be viewed as a bioactive ingredient with measurable potential, but always within the perimeter of real clinical evidence.

• In type 2 diabetes, the clinical signal has been more studied.
• In metabolic syndrome, multiple simultaneously altered factors are important.
• In PCOS, insulin resistance is a central pathophysiological node.
• Other areas, such as neuroprotection and oncology, remain preliminary.

The literature on cinnamon is very extensive and, precisely for this reason, requires careful reading. Alongside clinical studies, i.e., studies conducted on humans to evaluate effects and safety, there are meta-analyses, which are quantitative syntheses of multiple research studies, and narrative reviews. However, the quality of the evidence is not uniform. Some results converge robustly, while others remain more fragile or strongly depend on the experimental context. The interpretative key is therefore not to seek absolute confirmation, but to understand where the signal is more stable and clinically plausible. In general, the most convincing profile concerns metabolic disorders, while neurological and oncological areas remain more exploratory, with data still preliminary and often heterogeneous [9,20,32,10].

From a biological point of view, this difference is not surprising. Cinnamon contains compounds that act on pathways involved in inflammation, oxidation, insulin signaling, and lipid metabolism. In other words, the molecular rationale is consistent with the outcomes observed in trials on metabolic parameters. However, mechanistic plausibility does not equate to demonstrating a full clinical benefit. This is why reviews on Cinnamomum, the botanical genus to which cinnamon species belong, and on cinnamaldehyde, one of its main compounds, emphasize the distinction between pharmacological potential and consolidated therapeutic application [8,5,11]. The most useful literature does not promise miraculous effects, but identifies areas where the spice's action appears measurable and biologically sound.

Meta-analyses constitute the most useful level of synthesis for navigating seemingly discordant results. The 2022 meta-analysis on patients with metabolic diseases confirmed overall benefits, but without eliminating heterogeneity among studies [9]. The 2025 meta-analysis in patients with type 2 diabetes reinforced interest in metabolic biomarkers, while the umbrella review from the same year reiterated that the totality of meta-analyses suggests a favorable, but not uniform, effect, and that the result depends on dosage, duration, and sample characteristics [20,10]. This is a crucial point, because cinnamon does not always produce the same effect in every study: the same substance, in different forms and doses, can show different results. The meta-analysis on blood pressure profile also showed a statistically significant benefit across 9 RCTs (randomized controlled trials) with 641 participants, but the effect was clearer with supplementation equal to or less than 2 g/day and lasting longer than 8 weeks [24].

The most concrete clinical evidence is seen in trials on diabetes and PCOS. PCOS, or polycystic ovary syndrome, is an endocrine-metabolic condition often associated with insulin resistance and menstrual cycle irregularities. The 2016 Iraqi trial on patients with poorly controlled type 2 diabetes showed an antidiabetic and antioxidant effect of cinnamon [22]. In 2007, in a small study of 15 women with PCOS, daily oral cinnamon for 8 weeks reduced insulin resistance compared to placebo [28]. In 2018, in a randomized, double-blind, placebo-controlled trial, 45 women with PCOS received 1.5 g/day for 6 months, with favorable results on insulin sensitivity and menstrual cyclicity [30,29]. These data are not enormous, but they are consistent with the metabolic rationale of the spice. For this reason, cinnamon is often treated as an adjuvant, not as a primary intervention. It is a realistic clinical role, supported by some evidence, but still limited by the heterogeneity of studies and the lack of definitive clinical endpoints.

Critical reading must also include endpoints, i.e., the measures used to evaluate the effect of an intervention. Many studies analyze fasting glycemia, insulin, HOMA-IR, lipid profile, blood pressure, and inflammatory markers. HOMA-IR, an acronym for Homeostasis Model Assessment of Insulin Resistance, is an index that estimates insulin resistance based on glycemia and insulinemia. These are important parameters, but often surrogate, meaning indirect indicators of metabolic health. This does not make them irrelevant, but it requires caution in transforming them into strong conclusions. The reduction of a biomarker, in fact, does not automatically coincide with a reduction in clinical events, such as heart attack, complicated diabetes, or mortality. Reviews on the pharmacological properties of the genus Cinnamomum and on cinnamaldehyde reiterate precisely this distinction between biological plausibility and clinical certainty [8,5,11]. In summary, the scientific message is clear: cinnamon shows useful and consistent signals in some metabolic areas, but the literature does not yet allow it to be considered a generalizable solution. This is where critical reading becomes indispensable to avoid confusing promising results with definitive evidence.

• Meta-analyses show a possible, but not uniform, effect on glycemia.
• Clinical trials are more convincing in pre-existing metabolic disorders.
• The response varies with dose, duration, and participant profile.
• The most commonly used endpoints remain biomarkers, not hard clinical outcomes.

When it comes to cinnamon, the question is not only about its potential benefits, but also about the correct way to use it. Safety depends on the botanical species, meaning the variety of the plant's origin, the quantity consumed, the frequency, and the commercial form. The most important point is the distinction between culinary use and concentrated use, because available data show very different contexts between spice and supplement. Cinnamon in cooking, in moderate quantities, normally falls within a reasonable dietary context. However, cassia can contain higher amounts of coumarin, a natural substance present in some plants, and this makes caution essential when consumption is frequent or when highly concentrated products are used [1,4].

The EFSA guideline on coumarin, i.e., the European Food Safety Authority, provides a clear reference: the tolerable daily intake is 0.1 mg/kg of body weight per day [1]. This data should not be interpreted as a prohibition, but as a criterion to distinguish moderate food use from excessive exposure. In practice, it means that cinnamon is not an ingredient to be used indiscriminately when the botanical form is unknown or when the product is very rich in cassia. Reviews of cassia describe a broad phytocomplex, meaning a set of plant compounds, with over 160 identified compounds, and reiterate the need to also consider toxicology, i.e., the study of the harmful effects of substances, when evaluating the product [4].

The distinction between powder, extract, and supplement remains central also from a safety perspective. Food powder is closest to daily use and, usually, the simplest to incorporate into a balanced diet. Extracts and supplements, on the other hand, concentrate the content and can be more difficult to interpret if the effective dosage is not well known. This does not mean they are inherently problematic, but that they require more attention. Reviews on the genus Cinnamomum indeed highlight that chemical composition varies greatly and that biological significance depends not only on the species, but also on the form of intake [8,3].

From a clinical point of view, this difference is also crucial for interpreting studies. Several works that evaluated the metabolic effects of cinnamon used measured doses and limited durations, with results to be interpreted in the context of nutritional intervention and not as an invitation to increase consumption indefinitely. The Cochrane review on diabetes reported oral monopreparations, mainly of cassia, with an average dose of 2 g/d for 4-16 weeks [23]. The meta-analysis on blood pressure showed a more evident effect with supplementation equal to or less than 2 g per day and a duration longer than 8 weeks [24]. These numbers help to understand that clinical literature works with contained quantities, not with free or cumulative uses.

Safety, therefore, depends not only on the substance, but on the context of use. Occasional use in cooking has a different meaning than daily intake of capsules or extracts, especially if the source is not well specified. This is also important because cinnamon is often perceived as "natural" and therefore automatically harmless, but naturalness does not replace risk assessment. A natural product can still require attention if it contains high quantities of bioactive compounds. For this reason, conscious choice must start from the simplest question: am I using a spice, a flavoring, or a functional preparation?

The distinction between Ceylon and cassia is useful precisely because it guides caution. Ceylon cinnamon is often preferable when use is frequent, while cassia should be read with more caution due to its potential coumarin contribution [1,4]. This is not an absolute hierarchy, but a practical rule of common sense. If the goal is to flavor food, a small amount of spice is generally sufficient. If, on the other hand, a concentrated product is intended, it is advisable to check its composition, standardization, and declared dose. Reviews on the genus Cinnamomum indeed remind us that the chemical profile is not uniform and that the product must be interpreted based on what it actually contains [8,3].

Another useful element concerns the relationship between food use and potential benefits. The metabolic, antioxidant, and inflammatory properties reported in the literature do not authorize exceeding safety thresholds. On the contrary, precisely because some cinnamon compounds show biological activity, it becomes important to respect the quantity and form of intake. Research on cinnamaldehyde, i.e., the main aromatic compound responsible for the characteristic odor, and other constituents suggests interesting mechanisms, but these mechanisms do not automatically translate into a benefit proportional to the dose. In many cases, physiology responds to moderate and well-defined exposures, not to indiscriminate increases.

For this reason, in daily practice, cinnamon should be treated as a useful spice, not as an ingredient to accumulate. Culinary use allows its aroma to be enhanced and the use of added sugars to be reduced, while supplementation should be reserved for more targeted and better controlled contexts. The general rule is simple: the more concentrated the form, the more attention is needed. The clearer the product label, the easier it is to use it responsibly. Safety, in this field, arises from the combination of correct information and real moderation.

• The quantity consumed changes significantly between culinary use and supplementation.
• Cassia cinnamon requires more attention due to coumarin.
• Ceylon cinnamon is often preferable if use is frequent.
• Concentrated forms should be interpreted with more caution.
• The product should be chosen according to the actual objective.