Scientific Book

Turmeric

Turmeric contains curcumin, a polyphenol studied for its anti-inflammatory properties and potential interactions with energy metabolism. Experimental research highlights the involvement of AMPK, PI3K/AKT/mTOR, and GLUT4, while clinical studies explore its effects on glycemia, insulin resistance, and inflammation, with inconsistent results. In the book "The Choice to Live in Health or Disease," Dr. A. Colonnese and R. Panzironi delve into these mechanisms and the importance of bioavailability, dosage, and formulation.

Cite this article
Colonnese, A. & Panzironi, R. (2026). Turmeric. The Choice to Live in Health or in Disease. https://lifesciencehub.info/en/la-scelta-di-vivere-in-salute-o-in-malattia/turmeric
The Choice to Live in Health or in Disease · ISBN 979-12-82692-03-8

DOI lsh.en.libro.31

  • Published 05/11/2026
  • Updated 05/11/2026
  • CURCUMIN
  • NF-ΚB
  • INSULIN RESISTANCE
  • PI3K/AKT/MTOR
  • AMPK
Infographic featuring turmeric, structures of three curcuminoids, and the molecular network between the insulin receptor, AMPK, mTOR, and GLUT4.
Diagram of curcuminoids—curcumin, demethoxycurcumin, and bisdemethoxycurcumin—and the pathways investigated experimentally: AMPK activation, modulation of PI3K/AKT/mTOR and NF-κB, GLUT4 translocation, and insulin signaling. It thus links turmeric to the regulation of cellular energy, inflammation, autophagy, and protein synthesis.

ABSTRACT

Turmeric contains curcumin and other curcuminoids, compounds studied for their anti-inflammatory, antioxidant, and immunomodulatory activities. In the book "La scelta di Vivere in Salute o in Malattia" (The Choice to Live in Health or Disease), Dr. A. Colonnese and R. Panzironi analyze their involvement in metabolic and cellular processes associated with chronic diseases. Curcumin can modulate NF-κB and the production of inflammatory cytokines, contributing to the control of oxidative stress. Scientific interest primarily concerns the connections between inflammation, insulin resistance, and energy regulation.

At the molecular level, experimental studies describe a modulation of PI3K/AKT/mTOR, a pathway involved in cell growth and survival. In various tumor models, curcumin attenuates its activity, associating it with reduced proliferation and increased apoptosis, autophagy, and, in some contexts, ferroptosis. In parallel, the activation of AMPK can counteract mTORC1, promoting the regulation of autophagy and lipid accumulation. Protective effects have been observed in models of hepatic steatosis, ovarian damage, testicular aging, and impairment of the intestinal barrier, without automatically demonstrating clinical benefits.

Clinical meta-analysis reports improvements in fasting glycemia, glycated hemoglobin, certain lipid profile parameters, and inflammatory markers. Reductions in insulin and the HOMA-IR index suggest possible effects on insulin sensitivity. Further studies describe benefits for joint pain, stiffness, and muscle recovery, as well as favorable results in rheumatoid arthritis, ulcerative colitis, psoriasis, osteoarthritis, and mood disorders associated with chronic diseases. The magnitude of the responses varies with formulation, dosage, and individual characteristics. Piperine can increase the absorption of curcumin, but the clinical advantages of the combination require confirmation.

Overall, curcumin represents a possible complementary modulator of immunometabolic processes. Oncological observations remain predominantly preclinical and do not demonstrate established therapeutic efficacy. Any potential use must be evaluated by considering bioavailability, the quality of the evidence, and individual conditions, within the context of a balanced diet, physical activity, and control of metabolic risk factors. Future research will need to clarify the actual transferability of experimental mechanisms to humans.

Turmeric and its intrinsic properties

Turmeric (Curcuma longa L.) is a spice obtained from the dried rhizome of a plant belonging to the Zingiberaceae family, the same family as ginger. It has been used for millennia not only as a culinary ingredient, prized for its intense yellow color and warm, slightly bitter flavor, but also as a medicinal remedy in Ayurvedic, Chinese, and Middle Eastern traditions. From an agricultural perspective, turmeric grows in tropical and subtropical environments with humid soil and high temperatures; the main producing countries are India (which accounts for over 70–80% of global production), Bangladesh, Pakistan, Sri Lanka, Indonesia, China, and Thailand. The biological quality of turmeric depends heavily on the botanical variety, soil type, climate, and the methods used for drying and grinding the rhizome—factors that directly influence the content of its bioactive compounds.

From a phytochemical perspective, turmeric is an extremely complex matrix, and this complexity explains the vast range of its biological effects. The primary drivers of its properties are curcuminoids, a class of lipophilic polyphenols that includes curcumin, demethoxycurcumin, and bisdemethoxycurcumin, with curcumin being the most abundant and widely studied component quantitatively. Alongside these phenolic compounds, the rhizome (a stem that grows underground) contains a volatile fraction rich in terpenoids, which contribute synergistically to the spice's overall anti-inflammatory, antioxidant, and immunomodulatory activity (Shahrajabian and Sun, 2024) [1]. It is important to emphasize that turmeric does not act as a single isolated molecule, but as a phytocomplex, in which the various components cooperate by modulating multiple biological pathways simultaneously.

One of the hallmarks of turmeric is its potent anti-inflammatory action, which manifests through the modulation of numerous key mediators of chronic inflammation. Curcumin is capable of inhibiting the activation of the NF-κB transcription factor, considered one of the primary "conductors" of the persistent inflammatory response, thereby reducing the production of cytokines such as TNF-α, IL-1β, and IL-6, as well as the expression of COX-2 (Cozmin et al., 2024) [2]. This mechanism is particularly relevant because low-grade chronic inflammation represents the common ground for many modern pathologies, from metabolic and cardiovascular diseases to neurodegenerative and oncological conditions. In simple terms, turmeric does not just "turn off the symptom," but acts upstream, reducing the signal that keeps inflammation constantly switched on.

Closely linked to its anti-inflammatory action is the antioxidant function of turmeric. Curcuminoids are able to both directly neutralize reactive oxygen species and enhance endogenous antioxidant systems, such as superoxide dismutase, catalase, and glutathione peroxidase. This dual effect allows for more stable protection of cell membranes, mitochondria, and DNA from chronic oxidative stress (Cozmin et al., 2024) [2]. It is as if turmeric reduces the "biological rust" that accumulates in cells when metabolic and inflammatory stress persists over time.

In recent years, scientific interest has also shifted toward the role of turmeric in chronic inflammatory metabolic diseases, such as metabolic syndrome, type 2 diabetes, obesity, and dyslipidemia. Experimental and clinical evidence indicates that curcumin improves insulin sensitivity, reduces fasting glycemia and HOMA-IR, and contributes to better control of glycated hemoglobin, suggesting a direct action on glucose metabolism (Vafaeipour et al., 2022) [3]. At the lipid level, turmeric is associated with a reduction in triglycerides and total cholesterol, with more variable but generally favorable effects on HDL. These benefits appear to stem from a combination of reduced adipose inflammation, improved liver function, and modulation of the intracellular pathways involved in lipogenesis (the metabolic process through which the liver converts carbohydrates like glucose and simple sugars, such as fructose, into new fatty acids) and fatty acid oxidation.

This view has been further reinforced by a second-level review that analyzed dozens of meta-analyses of randomized clinical trials, showing how curcumin consistently reduces the main biomarkers of systemic inflammation (CRP, IL-6, TNF-α), oxidative stress (malondialdehyde), and glycemic dysfunction (fasting glycemia, insulin, and HOMA-IR) in chronic inflammatory metabolic diseases (Lee and Kim, 2024) [4]. A particularly relevant finding is that these effects are reproducible across different populations, suggesting a robust underlying mechanism, even if modulated by the bioavailability of the various formulations.

An aspect of great interest concerns aging and cardiometabolic diseases in the elderly. In this phase of life, low-grade chronic inflammation and oxidative stress—the so-called "inflammaging"—represent one of the main drivers of the loss of metabolic function. A systematic review of randomized clinical trials has shown that curcumin supplementation in the elderly is associated with a reduction in CRP, an improvement in insulin sensitivity, a decrease in triglycerides, and a reduction in systolic blood pressure, outlining an action profile consistent with global support for cardiometabolic health (Rajabinasab et al., 2025) [5]. In this case as well, turmeric appears to act as a modulator of the "biological terrain" rather than as an isolated symptomatic intervention.

Finally, the broader literature on turmeric highlights how its properties also extend to the oncological, radioprotective, immunomodulatory, and regenerative fields. Curcumin interferes with numerous pathways involved in cell proliferation, tumor survival, and stress response, including the PI3K/AKT/mTOR insulin pathway, promoting apoptosis, autophagy, and the reduction of angiogenesis (Cozmin et al., 2024) [2]. At the same time, it shows a unique ability to protect healthy tissues from oxidative and inflammatory damage induced by radiation, making it a compound of great interest as an adjuvant in complex clinical contexts.

Taken together, these data define turmeric as a profoundly biological spice, capable of interacting with the main pathogenetic nodes of modern diseases: chronic inflammation, oxidative stress, metabolic dysfunction, and loss of control over cellular processes. Once again, the key message is that its potential emerges fully only if integrated within a consistent lifestyle, in which diet, glycemic control, and the reduction of hyperinsulinemia create the appropriate context for these mechanisms to translate into real and lasting benefits.

Turmeric and supplementation in humans

When moving from the molecular properties of turmeric to its practical application in humans, the picture that emerges is surprisingly consistent: the benefits observed in experimental models are also confirmed in controlled clinical studies, especially in the context of chronic metabolic and inflammatory diseases. In this scenario, turmeric and its main constituent, curcumin, act as nutraceutical tools capable of supporting lifestyle and standard therapies, not by replacing them, but by enhancing their efficacy.

One of the most studied areas is glucose metabolism in type 2 diabetes, prediabetes, and metabolic syndrome. An updated systematic review with meta-analysis, which included 28 randomized clinical trials, demonstrated that supplementation with Curcuma longa or its curcuminoids is associated with a significant reduction in fasting glycemia and glycated hemoglobin. On average, fasting glycemia is reduced by approximately 8 mg/dL and HbA1c by approximately 0.13%—a figure that may seem modest but is clinically relevant if maintained over time, as it translates into a reduction in the risk of micro- and macro-vascular complications (Pathomwichaiwat et al., 2023) [6]. It is particularly interesting that these effects were consistent regardless of the formulation used, suggesting that the benefit derives from an underlying biological action rather than a single technological vehicle.

This evidence is reinforced by a dose-response meta-analysis that included 59 randomized clinical trials, showing that supplementation with turmeric or curcumin significantly reduces fasting glycemia, serum insulin, HbA1c, and HOMA-IR. In practical terms, this indicates an improvement in both the average level of circulating glucose and insulin sensitivity, suggesting that curcumin does not act only “downstream” on glycemia, but contributes to making insulin signaling more efficient (Dehzad et al., 2023) [7]. It is as if turmeric helps reduce the metabolic background noise that forces the pancreas to produce more and more insulin to achieve the same effect.

This action becomes even more evident in analyses focused exclusively on type 2 diabetes. A quantitative meta-analysis that included 18 clinical studies for a total of over 1,300 patients showed that curcumin reduces fasting glycemia by over 11 mg/dL and HbA1c by approximately 0.5%, accompanying these effects with a significant reduction in C-reactive protein, a key marker of systemic inflammation (Mokgalaboni et al., 2024) [8]. This finding is particularly relevant because it confirms that the improvement in glycemic control does not occur in isolation, but is part of a broader attenuation of the low-grade inflammatory state that characterizes type 2 diabetes.

A similar picture also emerges in specific endocrine-metabolic contexts such as polycystic ovary syndrome (PCOS), a condition in which insulin resistance, inflammation, and oxidative stress reinforce each other. A systematic review with dose-response meta-analysis showed that curcumin supplementation in women with PCOS significantly improves fasting glycemia, serum insulin, and HOMA-IR, indicating a recovery of insulin sensitivity. It is interesting to note that these benefits manifest even in the absence of a significant reduction in body weight, suggesting that the metabolic effect of curcumin does not depend exclusively on weight loss, but on a direct modulation of the intracellular pathways involved in glucose metabolism (Mohammadi et al., 2025) [9]. Total cholesterol is also reduced, outlining a favorable cardiometabolic profile.

Alongside glucose metabolism, clinical literature has explored the role of turmeric in musculoskeletal health, an area often overlooked but central to chronic diseases and aging. A systematic review with meta-analysis of 21 randomized clinical trials showed that turmeric extracts and curcumin supplements significantly improve joint pain, stiffness, functionality, and muscle recovery, with a favorable safety profile and a low incidence of adverse effects (Doyle et al., 2023) [10]. It also emerged that formulations with higher bioavailability, such as water-dispersible extracts, are more effective even at relatively low dosages, highlighting how the delivery technology plays a key role in translating biological potential into clinical benefit.

Taken together, these clinical studies outline a clear message: turmeric and curcumin do not act as simple natural hypoglycemic agents, but as systemic modulators of inflammation, oxidative stress, and insulin signaling. The improvement in glycemic parameters observed in the studies is a reflection of a deeper action, which involves the reduction of chronic inflammation, the improvement of insulin sensitivity, and the stabilization of the overall metabolic terrain.

Once again, a key concept already encountered in other chapters emerges: the efficacy of turmeric also depends on the context. The benefits observed in clinical studies find their maximum expression when supplementation is part of a lifestyle oriented toward reducing glycemic variability, hyperinsulinemia, and low-grade inflammation. In this scenario, turmeric is not a shortcut, but a biological ally capable of supporting and amplifying the metabolic rebalancing processes already underway.

Turmeric and its uses for treated conditions

When observing the effects of turmeric on various chronic diseases, a common thread clearly emerges that links seemingly distant fields such as diabetes, autoimmunity, cancer, and mood disorders. This thread is represented by low-grade chronic inflammation, oxidative stress, and metabolic dysfunction—three elements that curcumin appears to modulate in a simultaneous and consistent manner. It is precisely this cross-cutting action that explains why turmeric finds application in such diverse clinical conditions.

In type 2 diabetes, curcumin has been studied both from a preventive perspective and as a therapeutic support. Preclinical evidence shows that curcumin improves pancreatic β-cell function, reduces their apoptosis, and improves insulin sensitivity in peripheral tissues, suggesting an action that is not limited to glycemic control but extends to the protection of the endocrine pancreas. Clinical studies confirm this picture: curcumin supplementation is associated with improvements in HbA1c, fasting glycemia, and inflammatory markers, indicating that the glycemic benefit is a reflection of a reduction in the systemic inflammatory load that accompanies the disease (Pivari et al., 2019) [11]. It is as if curcumin acts by lightening the “metabolic pressure” that forces the body to maintain chronically high levels of insulin.

This ability to modulate inflammation and immune response becomes even more evident in the context of autoimmune diseases. A systematic review with meta-analysis of 31 randomized clinical trials has shown that curcumin and Curcuma longa extracts produce significant clinical benefits in various autoimmune diseases, with particularly solid evidence in ulcerative colitis, rheumatoid arthritis, and psoriasis. In these conditions, treatment with curcumin has been associated with a reduction in disease activity, improvement of symptoms, and a decrease in inflammatory markers, often as an adjunct treatment to standard therapy. Even in conditions such as systemic lupus erythematosus, multiple sclerosis, and Crohn's disease, available data suggest favorable effects, although they remain preliminary. This profile is consistent with the ability of curcumin to inhibit NF-κB, modulate cytokine production, and promote a rebalancing between pro-inflammatory and regulatory immune cells (Zeng et al., 2022) [12].

The role of turmeric also extends to chronic inflammatory complications, such as osteoarthritis, inflammatory respiratory diseases, functional gastrointestinal disorders, and cardiovascular conditions. Clinical evidence indicates that, in osteoarthritis, curcumin reduces pain and joint stiffness with efficacy comparable to NSAIDs (non-steroidal anti-inflammatory drugs), but with better gastrointestinal tolerability, suggesting an anti-inflammatory action that is effective yet more “physiological.” In other contexts, such as irritable bowel syndrome or psoriasis, results show improvements in symptoms and quality of life, consistent with the modulation of mucosal and cutaneous inflammation (Zafar et al., 2025) [13]. Once again, the message that emerges is that curcumin does not selectively turn off a single symptom, but reduces the biological environment that fuels it.

In the oncological field, curcumin has been studied as a chemopreventive agent and as a potential adjuvant to conventional therapies. Updated reviews show that curcumin interferes with numerous key processes of tumorigenesis, including cell proliferation, invasiveness, angiogenesis, and resistance to apoptosis, by modulating several pathways, including PI3K/AKT/mTOR (Yang et al., 2022) [14]. Its ability to induce apoptosis and autophagy suggests an action of “normalizing” the aberrant growth signals typical of tumor cells. Although clinical evidence is still limited and constrained by low bioavailability, the favorable safety profile makes curcumin an interesting candidate as an integrative support, rather than a substitute for oncological therapies.

An often overlooked area, but one of great clinical relevance, is that of mood disorders associated with chronic diseases. Depression and anxiety are frequent comorbidities in conditions such as diabetes, obesity, arthritis, and inflammatory bowel diseases, and they share an inflammatory and oxidative basis with the latter. A systematic review with meta-analysis has shown that curcumin significantly reduces depressive symptoms and, to a more moderate but consistent extent, anxious symptoms in patients with chronic diseases (Yuan et al., 2025) [15]. From a biological point of view, these effects can be explained through the reduction of neuroinflammation and the activation of antioxidant pathways. It is as if curcumin reduces the “biological weight” that chronic disease exerts on the emotional brain, improving not only clinical parameters but also the subjective perception of health.

Taken together, this evidence outlines turmeric as a therapeutic spice with a systemic vocation, capable of intervening on pathogenic nodes common to many of the diseases treated in this book: chronic inflammation, oxidative stress, immune dysfunction, and metabolic alterations. Its value does not lie in being a “natural cure,” but in acting as a modulator of the biological terrain, supporting rebalancing processes when included in a consistent lifestyle oriented toward glycemic stability, the reduction of hyperinsulinemia, and the control of inflammation. It is in this context that turmeric fully expresses its potential, not as an isolated intervention, but as an integral part of an integrated and conscious strategy.

Turmeric and the improvement of insulin resistance

One of the most interesting aspects of curcumin concerns its ability to intervene directly in the biological mechanisms underlying insulin resistance, a condition that represents the pathophysiological core of type 2 diabetes, metabolic syndrome, non-alcoholic fatty liver disease, and many modern cardiovascular diseases. In the presence of insulin resistance, peripheral tissues progressively lose their ability to respond correctly to insulin, forcing the pancreas to produce ever-increasing amounts of the hormone to keep glycemia stable. This state of chronic hyperinsulinemia contributes to keeping the PI3K/AKT/mTOR pathway constantly active, promoting systemic inflammation, lipid accumulation, and a progressive loss of metabolic flexibility.

In this context, curcumin appears to act as a multifactorial metabolic modulator. A vast umbrella review of available meta-analysis has highlighted that curcumin is associated with a reduction in glycemia, an improvement in insulin sensitivity, and a decrease in plasma insulin levels (Xu et al., 2025) [16]. The authors also emphasize that these effects seem to stem from curcumin's ability to activate nuclear receptors, improve pancreatic β-cell function, and reduce oxidative stress, all of which are elements closely involved in the development of insulin resistance. From a physiological standpoint, this means that curcumin does not simply lower glycemia "artificially," but contributes to improving the body's ability to manage glucose more efficiently.

This framework is also confirmed by systematic reviews dedicated specifically to type 2 diabetes. An analysis of eleven randomized clinical trials showed that supplementation with curcumin leads to a significant reduction in fasting glycemia and glycated hemoglobin, with improvements in the HOMA-IR index in numerous studies (Mahdavi et al., 2021) [17]. The most evident effects were observed in treatments lasting longer than twelve weeks, suggesting that curcumin acts through a progressive metabolic rebalancing rather than an immediate pharmacological effect. This aspect is particularly important because insulin resistance is a chronic condition that develops slowly over time and is difficult to modify through rapid, isolated interventions.

From a biological perspective, one of the most relevant mechanisms appears to be curcumin's ability to reduce chronic inflammation and oxidative stress, two of the main factors that fuel insulin resistance. Curcumin modulates the NF-κB pathway, reduces the production of pro-inflammatory cytokines, and improves the activity of endogenous antioxidants (Mahdavi et al., 2021) [17]. It is as if curcumin helps to "defuse" the chronic inflammatory microenvironment that, over time, makes tissues increasingly less sensitive to insulin.

The most robust evidence, however, comes from the most recent umbrella meta-analysis on glycemic indices. A review comprising 22 meta-analysis highlighted that supplementation with curcumin significantly reduces fasting glycemia, HbA1c, HOMA-IR, and plasma insulin levels (Zheng et al., 2024) [18]. Particularly interesting is the fact that the best effects were observed with dosages exceeding 1 gram per day and with supplementation periods longer than 10 weeks, suggesting a dose-time relationship consistent with a progressive improvement in insulin sensitivity.

The authors also emphasize that curcumin appears to activate AMPK, one of the main cellular energy sensors, promoting peripheral glucose utilization and reducing hepatic gluconeogenesis (Zheng et al., 2024) [18]. This step is extremely important because it directly links the effects of curcumin on glucose metabolism with what was observed in the previous paragraphs regarding the relationship between AMPK and mTOR. By activating AMPK, curcumin not only improves glucose uptake but also helps to reduce the continuous anabolic activation sustained by mTOR in conditions of chronic hyperinsulinemia.

A particularly interesting role also emerges from the combination of curcumin and piperine. Due to the limited oral bioavailability of curcumin, piperine, an alkaloid present in black pepper, appears to significantly increase its absorption and biological efficacy. A systematic review with meta-analysis on patients with prediabetes and type 2 diabetes showed that combined supplementation with curcumin and piperine produces numerical improvements in fasting glycemia, HOMA-IR, and BMI (Widjanarko et al., 2024) [19]. Although some results did not reach statistical significance, the observed metabolic trend suggests a potential favorable effect on insulin sensitivity, especially considering the still limited number of available studies.

This data takes on particular relevance when considering that bioavailability represents one of the main clinical limitations of curcumin. Piperine appears to increase the intestinal absorption of curcumin through the inhibition of hepatic and intestinal glucuronidation (the most important detoxification reaction in our body), allowing for higher and more biologically active plasma concentrations (Widjanarko et al., 2024) [19]. In other words, black pepper does not just accompany turmeric in culinary tradition, but could concretely amplify its metabolic effects.

This synergy emerges with even greater clarity in the most recent systematic reviews on cardiometabolic diseases. A review of twenty randomized controlled clinical trials showed that the curcumin-piperine combination significantly improves fasting glycemia, HbA1c, and HOMA-IR in subjects with metabolic syndrome and type 2 diabetes. In parallel, improvements in systemic inflammation, oxidative stress, lipid profile, and visceral adiposity were observed. The authors attribute these effects primarily to the activation of AMPK, the reduction of hepatic gluconeogenesis, and the modulation of inflammatory pathways such as NF-κB (Pan et al., 2026) [20].

From a pathophysiological point of view, this is a central concept: insulin resistance is not simply a "sugar disease," but a systemic condition characterized by chronic inflammation, mitochondrial dysfunction, lipid alterations, and continuous overstimulation of the insulin pathway. Curcumin appears to intervene simultaneously at all these levels, helping to break one of the main vicious cycles of modern metabolism.

Overall, the available evidence shows that turmeric does not act as a simple hypoglycemic agent, but as an integrated modulator of metabolic physiology. By improving insulin sensitivity, inflammation, oxidative stress, lipid metabolism, and cellular energy homeostasis, curcumin appears to help reduce the metabolic burden imposed by chronic hyperinsulinemia and the continuous activation of mTOR.

In this sense, the relationship between turmeric and insulin resistance represents one of the most complete examples of how a natural compound can interact with the main biological mechanisms involved in modern metabolic diseases, offering physiologically consistent support within a broader strategy based on nutrition, glycemic control, and the reduction of chronic inflammation.

Turmeric and its relationship with mTOR

To fully understand the role of turmeric in the context of metabolic, immune, and proliferative diseases, it is necessary to focus on its relationship with mTOR, one of the main integration nodes between nutrition, hormonal signals, energy status, and cell fate. mTOR can be imagined as a command center that decides whether a cell should grow, produce proteins, store energy, or activate recycling and repair processes such as autophagy. When this system remains chronically hyperactive, as occurs in conditions of hyperinsulinemia, persistent inflammation, and nutritional overload, the result is a loss of metabolic flexibility that promotes chronic and proliferative diseases.

In this scenario, curcumin emerges as one of the most studied phytocompounds for its ability to directly and indirectly modulate the PI3K–AKT–mTOR insulin pathway, not by acting as a brutal inhibitor, but rather as a fine-tuner of the signal. A broad and updated meta-analysis highlights how curcumin is able to reduce the hyperactivation of mTORC1, promoting the restoration of autophagy and improving the cellular response to oxidative stress and inflammation (Khayatan et al., 2025) [21]. This aspect is crucial because mTORC1 represents one of the main physiological brakes on autophagy: when the brake is partially released, the cell can return to "performing maintenance," eliminating damaged proteins and dysfunctional organelles.

Experimental evidence shows that this modulation does not occur in isolation, but involves the entire upstream cascade. In numerous cellular models, curcumin reduces the activation of PI3K and AKT, with a consequent decrease in the phosphorylation of mTOR and its downstream effectors (Aliyari et al., 2025) [22]. This means that the growth and survival signal, often amplified in pathological conditions, is progressively attenuated. From a conceptual point of view, it is as if curcumin were turning down the volume of a signal that, over time, becomes deafening for the cell.

This action is particularly evident in oncological contexts, where the hyperactivation of mTOR supports uncontrolled proliferation, stress resistance, and metabolic adaptation. In lung carcinoma cells, curcumin has been shown to inhibit the PI3K/AKT/mTOR pathway in a dose- and time-dependent manner, simultaneously inducing apoptosis and autophagy (Liu et al., 2018) [23]. The combined use of curcumin with rapamycin, a selective mTOR inhibitor, further enhanced these effects, confirming that mTOR represents a key node in the mechanism of action. This finding is important because it shows that curcumin does not act randomly, but targets a precise and well-characterized pathway.

A similar picture also emerges in human melanoma, a neoplasm strongly dependent on the AKT/mTOR axis. In this context, curcumin reduces proliferation and invasiveness, induces cell cycle arrest, and activates autophagy, with a clear reduction in the phosphorylation of AKT and mTOR, both in vitro and in in vivo models (Zhao et al., 2016) [24]. Here, autophagy seems to take on a pro-death role, synergistic with the inhibition of growth signals, suggesting that curcumin can push the tumor cell toward an irreversible loss of adaptive capacity.

The link between curcumin, mTOR, and cell fate becomes even more sophisticated when considering the role of ferroptosis, a form of cell death distinct from apoptosis. In gastric cancer models, curcumin induces ferroptosis through the suppression of the PI3K/AKT/mTOR pathway, with an increase in intracellular iron (Zheng et al., 2024) [25]. In this case, the inhibition of mTOR not only promotes autophagy but also creates the metabolic conditions that make the cell vulnerable to ferroptosis. It is as if curcumin were leading the tumor cell into a dead end, where survival mechanisms are progressively deactivated.

A particularly relevant aspect, which broadens the discussion beyond oncology, is that the modulation of mTOR by curcumin does not translate exclusively into cell death. Under conditions of moderate stress, the reduction of mTORC1 can promote "protective" autophagy, which is useful for restoring cellular homeostasis. This dual register, cytoprotective or cytotoxic depending on the context, is consistent with the physiological function of mTOR as a sensor of cellular quality (Khayatan et al., 2025) [21]. In other words, curcumin does not force a single outcome, but helps to restore the cell's ability to choose correctly between adaptation and self-destruction.

This vision is reinforced by the role of curcumin in the dialogue between mTOR and other signaling networks. By reducing inflammation and oxidative stress, curcumin lightens part of the burden that keeps mTOR chronically active, especially in metabolic and immune diseases (Aliyari et al., 2025) [22]. In this sense, the modulation of mTOR is not an isolated effect, but the result of a broader rebalancing of the cellular microenvironment.

Overall, these studies outline curcumin as a multifactorial modulator of mTOR, capable of reducing the pathological hyperactivation of the pathway, reactivating autophagy, promoting the elimination of irreversibly damaged cells, and improving cellular resilience in less extreme contexts. It is fundamental to emphasize that this action is particularly consistent with a lifestyle-based approach: in the presence of chronic hyperinsulinemia and nutritional overstimulation, mTOR remains constantly on; curcumin, on the other hand, acts as a "downsizing" signal, helping the body to exit a forced and continuous growth mode. In this sense, the relationship between turmeric and mTOR represents one of the most solid points of contact between nutrition, metabolism, and modern cell biology, and provides a rational basis for the use of turmeric as an integrative support in pathologies where the insulin–mTOR axis is dysregulated, always within an overall strategy aimed at reducing glycemic variability, hyperinsulinemia, and chronic inflammation.

Turmeric, AMPK, and the metabolic rebalancing of mTOR

If in the previous paragraph we observed how curcumin is able to directly reduce the hyperactivation of the PI3K/AKT/mTOR pathway, there is a further level of regulation that is even deeper and biologically refined: that exerted through AMPK, the main cellular energy sensor. Understanding this relationship is fundamental, because AMPK and mTOR represent two opposite and complementary metabolic programs. When nutrients, glucose, and insulin are constantly elevated, mTOR promotes cell growth, protein synthesis, and energy storage. When, on the other hand, the cell perceives metabolic stress or reduced energy availability, AMPK slows down anabolic processes, promotes energy conservation, and reactivates autophagy. In other words, mTOR pushes the cell toward continuous growth, while AMPK brings it back toward a mode of maintenance, adaptation, and metabolic survival.

In this context, curcumin shows an extraordinary ability to restore the balance between these two systems. One of the most interesting examples emerges from studies on ovarian damage induced by oxidative stress. In experimental models of ovarian dysfunction, curcumin has been shown to significantly reduce the apoptosis of granulosa cells (fundamental somatic cells present in the mammalian ovary), improve follicular architecture, and restore autophagic balance through the activation of AMPK and the concomitant inhibition of mTOR (Duan et al., 2024) [26]. This finding is particularly important because ovarian cells are extremely vulnerable to the excess of reactive oxygen species and the hyperactivation of metabolic pathways associated with cellular stress. Curcumin therefore seems to act as a “metabolic corrector,” returning the cell to a more protective and less dysfunctional mode.

The most interesting aspect that emerged from this study concerns the role of autophagy. Oxidative stress, in fact, induces an altered and disorganized autophagic response that, instead of protecting the cell, can contribute to follicular degeneration. Curcumin has shown the ability to normalize this process through the modulation of the AMPK/mTOR axis (Duan et al., 2024) [26]. In biological terms, it is as if curcumin helps the cell to “find the correct rhythm” of its internal repair processes, avoiding both the blockage of autophagy and its excessive destructive activation.

This ability to rebalance AMPK and mTOR also emerges with great clarity in hepatic metabolism. In specific cells exposed to high concentrations of glucose, a condition that simulates the metabolic environment of diabetic fatty liver, curcumin significantly reduced intracellular lipid accumulation through the activation of AMPK and the suppression of mTOR signaling (Chen et al., 2025) [27]. Concurrently, a reduction in the expression of two key enzymes of hepatic lipogenesis was observed. This step is extremely relevant because it demonstrates how curcumin does not limit itself to exerting a generic antioxidant action, but intervenes directly on the metabolic programs that regulate lipid synthesis and accumulation.

From a pathophysiological point of view, this mechanism appears perfectly consistent with what happens in conditions of chronic hyperinsulinemia. When glucose and insulin remain elevated over time, mTOR remains constantly active, favoring lipogenesis, triglyceride accumulation, and progressive fatty liver. The activation of AMPK by curcumin, on the other hand, represents an opposite signal: it increases fatty acid oxidation, reduces anabolic processes, and brings metabolism back toward a more energetically efficient mode (Chen et al., 2025) [27]. It is as if the hepatic cell progressively stops “storing” energy and returns to using it in a more physiological manner.

A similar picture also emerges in models of male reproductive aging. In testicular cells and murine testes exposed to D-galactose (a simple sugar present mainly in milk, where it joins glucose to form lactose), curcumin significantly improved the integrity of the blood-testis barrier through the activation of autophagy mediated by the AMPK/mTOR pathway. Cellular aging was associated with a reduction in tight junction proteins, an increase in markers of senescence (cells that have stopped dividing but remain metabolically active in tissues), and suppression of autophagy; treatment with curcumin reversed all these alterations (Xue et al., 2025) [28].

This aspect is particularly interesting because it shows how the regulation of AMPK and mTOR by curcumin does not only concern energy metabolism, but also the maintenance of the structural integrity of tissues. Autophagy, in fact, does not simply represent a “degradation” mechanism, but one of the main cellular maintenance systems through which the organism eliminates damaged components and preserves tissue functionality during aging.

The same logic also emerges in the intestinal context. In a murine model of colorectal adenoma, curcumin reactivated the autophagic flux through the modulation of the AMPK/mTOR pathway. In parallel, a significant improvement in the integrity of the intestinal mucosal barrier was observed, with an increase in certain specific proteins. This finding is biologically very important because intestinal barrier dysfunction represents one of the main amplifiers of chronic metabolic inflammation and the pathological activation of the insulin pathway (Wang et al., 2025) [29].

Overall, these studies outline an extremely consistent picture: curcumin does not act as a simple mTOR inhibitor, but as a modulator of the entire cellular energy balance. Through the activation of AMPK and the reduction of mTOR hyperactivation, curcumin promotes autophagy, cellular resilience, control of lipogenesis, tissue protection, and the maintenance of metabolic homeostasis.

This concept is particularly relevant in the modern context, characterized by chronic caloric excess, persistent hyperinsulinemia, and continuous anabolic overstimulation. In these conditions, mTOR tends to remain constantly switched on, while AMPK is progressively “silenced.” Curcumin, on the other hand, seems to restore the physiological dialogue between these two systems, bringing the cell back toward a condition of greater metabolic flexibility and adaptive capacity. In this sense, the relationship between turmeric, AMPK, and mTOR represents one of the most advanced examples of how a natural compound can interact with the main cellular energy sensors, helping to counteract the metabolic and proliferative alterations associated with the modern Western lifestyle.

Conclusions

Turmeric is an example of how a traditional spice can influence numerous biological processes. Our journey began with its properties, primarily linked to curcumin and other curcuminoids. These substances exhibit anti-inflammatory, antioxidant, and immunomodulatory activities, intervening in mechanisms involved in the development of many chronic diseases. In particular, curcumin can reduce NF-κB activity and the production of inflammatory cytokines, contributing to the protection of cells from oxidative stress.

From these properties, we moved on to clinical evidence to understand what benefits have been observed in humans. Meta-analyses report improvements in fasting glycemia, glycated hemoglobin, and certain lipid parameters. Reductions in inflammatory markers and benefits regarding joint pain, stiffness, and muscle recovery have also been observed. However, the magnitude of the effects varies according to dosages and participant characteristics. Indeed, the bioavailability of curcumin is an important factor in interpreting the results.

Broadening our view to the conditions treated, we encountered applications involving various body systems. In type 2 diabetes, curcumin can contribute to glycemic control and the reduction of inflammation. In autoimmune diseases, some research reports clinical improvements, particularly in rheumatoid arthritis, ulcerative colitis, and psoriasis. Interesting results also emerge in osteoarthritis and mood disorders associated with chronic diseases. In oncology, however, the evidence remains primarily experimental and does not demonstrate established therapeutic efficacy in humans.

The link between these conditions leads to one of the central themes of the chapter: insulin resistance. When tissues respond less effectively to insulin, the pancreas increases hormone production to keep glycemia stable. Curcumin appears to help counteract this imbalance by reducing inflammation, oxidative stress, and metabolic alterations. Clinical studies report improvements in the HOMA-IR index and insulin levels, suggesting possible benefits for insulin sensitivity. We also observed how the combination with piperine can increase the absorption of curcumin, although the clinical benefits of this combination require further confirmation.

But through which cellular mechanisms do these effects develop? The answer involves the PI3K/AKT/mTOR pathway, which is fundamental in regulating cell growth and survival. In various tumor models, curcumin reduces its activity, limiting proliferation and promoting apoptosis (programmed cell death), autophagy (a process that eliminates and recycles damaged cellular components), and, in some contexts, ferroptosis. The latter represents a form of cell death associated with iron and oxidative damage to membranes.

These results show how the regulation of mTOR by curcumin can influence cell fate. However, the control of this pathway does not only concern cell growth and survival, but also involves the mechanisms that regulate energy utilization. In this balance, AMPK—the main cellular energy sensor—takes on particular importance, as it is capable of counteracting mTORC1 activity under certain conditions. Experimental studies show that curcumin can indeed activate AMPK and reduce mTOR activity, favoring the control of fat accumulation and the regulation of autophagy. Through these mechanisms, protective effects have been observed in experimental models of ovarian damage, hepatic steatosis, testicular aging, and impairment of the intestinal barrier.

Thus, the central message of the chapter emerges: turmeric can influence the mechanisms that link inflammation, insulin sensitivity, and cellular energy balance. Clinical evidence suggests a possible complementary role, while many molecular applications require further confirmation in humans. Its value must therefore be considered within a broader strategy based on a balanced diet, physical activity, and the control of metabolic risk factors.

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