Mediterranean, MIND, and ketogenic diets in Alzheimer's disease: mechanistic coherence and clinical uncertainty
Year: 2026
Type: article
Abstract: Alzheimer's disease is a neurodegenerative encephalopathy characterized by the accumulation of β-amyloid (Aβ) plaques and neurofibrillary tangles composed of tau proteins (1). However, disease progression does not occur solely through Aβ deposition; it also involves a sustained neuroinflammatory response (2,3). Aβ acts as a damageassociated molecular pattern (DAMP), activating microglial receptors and triggering pathways such as NF-κB and the NLRP3 inflammasome, leading to the release of proinflammatory cytokines.These cytokines induce astrocytes to adopt a more inflammatory phenotype, further amplifying inflammation and increasing blood-brain barrier permeability (3,4).In addition to Aβ acting as a DAMP, Saturated Fatty Acids (SFAs) induces a metabolic state that amplifies TLR4-dependent inflammatory signaling. The key point here is that SFAs do not activate the receptor directly, but take advantage of a metabolic priming state of the cell to amplify inflammatory stress, and this corroborates the idea that diet can, in practice, dictate the pace of inflammation in the central nervous system (5). The increased consumption of SFAs among younger populations suggests that this pro-inflammatory pattern is starting earlier in life, reinforcing the urgent need for preventive strategies in early stages to mitigate long-term neurological impacts.Considering the neuroinflammatory profile of Alzheimer's disease, dietary patterns appear to play a notable role in modulating the risk and possibly the progression of the disease (6). Widely investigated patterns such as MIND, ketogenic, and Mediterranean diets seem to share convergent characteristics, including anti-inflammatory and antioxidant profiles, as well as favorable effects on insulin sensitivity, vascular function, and metabolic homeostasis. From a biological perspective, it is assumed that modulating peripheral inflammation, oxidative stress, and energy metabolism could positively influence mechanisms implicated in amyloid deposition, tau pathology, and cognitive decline (6,7).The mechanistic basis of this protection lies in the synergy between unsaturated fatty acids and bioactive compounds that regulate inflammation and mitochondrial function (8)(9)(10)(11)(12). Among these components, dietary fiber stands out for its conversion into short-chain fatty acids (SCFAs) via the gut microbiota (13,14). Metabolites such as butyrate and propionate not only preserve the integrity of the blood-brain barrier, but also modulate the inflammatory state of microglia, directly connecting dietary patterns to central neuroinflammatory control (13,14).Meta-analyses of observational studies indicate consistent associations between greater adherence to the Mediterranean or MIND diets and a lower risk of dementia or Alzheimer's disease, with relative risk reductions potentially relevant at the population level (15,16). However, these findings are accompanied by methodological heterogeneity, risk of residual confounding, and the possibility of reverse causality.When randomized clinical trials are evaluated, the effects appear to be more discrete. Interventions based on the MIND pattern or on caloric restriction have demonstrated modest cognitive improvements and, in many cases, observed effects no superior to those of active controls (17,18). Similarly, ketogenic approaches show short-term symptomatic benefits; however, evidence remains insufficient regarding sustained risk modification or disease progression in Alzheimer's disease, in addition to the challenges related to long-term adherence and metabolic safety (19,20). This divergence between consistent epidemiological associations and modest experimental effects suggests that part of the observed risk reduction may reflect not only the isolated dietary pattern itself, but perhaps a shift from a previous dietary pattern, including reduced intake of ultra-processed foods and potentially lower caloric intake, and, more broadly, a healthier overall lifestyle phenotype. Summary of methodological characteristics, main findings, limitations, and clinical implications of studies evaluating the Mediterranean, MIND, and ketogenic diets in relation to cognitive outcomes and Alzheimer's disease.Currently, there appears to be a growing focus on studies investigating the role of the ketogenic diet in the field of Alzheimer's disease (19)(20)(21)(22). This growing interest appears to be driven largely by the metabolic rationale underlying the hypothesis, rather than by robust clinical evidence. The idea that Alzheimer's disease may represent, at least in part, a state of "cerebral glucose hypometabolism" has led to the hypothesis that ketone bodies could function as an alternative fuel, potentially bypassing neuronal energy deficits. Experimental studies suggest that β-hydroxybutyrate influences inflammatory signaling, including the NLRP3 inflammasome, oxidative stress, mitochondrial function, and BDNF expression, and, in preclinical models, the results are often consistent and biologically plausible (19,23,24).It is important to differentiate classical ketogenic diets, modified ketogenic approaches, medium-chain triglyceride-based protocols, and exogenous ketone strategies, as the lack of standardization across studies may contribute to the observed clinical uncertainty (25). When translated into clinical trials, the magnitude of the effect tends to be modest and predominantly symptomatic, with short-term benefits in cognitive scores and a lack of convincing evidence for structural modification of AD progression (19,20). Furthermore, interventions are heterogeneous, short-term, and involve small sample sizes.In addition, long-term adherence to a ketogenic diet is challenging for older populations, who are often polymedicated and metabolically fragile. This fragility poses specific clinical risks such as sarcopenia and micronutrient deficiencies resulting from strict food group restrictions-deficits that impair immune function, gut health, and metabolic resilience. Moreover, the elevation of LDL-C and triglycerides observed in some studies is not trivial; such lipid profile changes should be viewed with caution, particularly in a population already at high cardiovascular risk (26)(27)(28).Thus, it is reasonable to question whether the pursuit of a highly restrictive "metabolic shortcut," disproportionate to global dietary patterns, is truly the most appropriate path forward.Diets such as the Mediterranean and MIND patterns, rich in vegetables, fiber, polyphenols, and mono-and polyunsaturated fatty acids, appear to modulate processes involved in the pathophysiology of Alzheimer's disease in a broader and more integrated manner (8,29,30). Bioactive compounds present in leafy greens, berries, olive oil, and nuts exhibit antioxidant and anti-inflammatory properties that attenuate NF-κB activation and reduce the production of pro-inflammatory cytokines (8)(9)(10)(11)(12)31).Polyphenols modulate amyloid precursor protein processing by favoring the non-amyloidogenic pathway and inhibiting BACE, in addition to interfering with Aβ oligomerization and facilitating its clearance. Furthermore, preclinical evidence suggests that these compounds may reduce tau hyperphosphorylation by modulating kinases, such as GSK-3β, and activating phosphatases, such as PP2A (9,10,31).Within the oxidative and mitochondrial axis, flavonoids such as quercetin, epicatechin, and anthocyanins act as free radical scavengers, stimulate endogenous antioxidant enzymes, and modulate pathways such as Nrf2 and PI3K/Akt, with implications for neuronal survival and synaptic plasticity (9,10,(32)(33)(34).The key here is the biochemical synergy within the food matrix itself-not just the isolated compounds. This explains the persistent gap between the benefits of whole dietary patterns and the frequent failure of individual polyphenol supplements to replicate them. Moreover, potential interactions with the gut microbiota-whose metabolites may influence inflammatory signaling and gut-brain axis communication-further support a biological explanation for a systemic effect rather than a purely localized one (11,12). Short-chain fatty acids (SCFAs) and urolithins stand out as likely mediators, with experimental data showing they can preserve microglial integrity. By reducing neuroinflammatory signaling, these microbial metabolites provide a plausible pathway for the neuroprotective effects observed in dietary studies (35).Prospective cohorts recently compiled in JAMA demonstrated that greater adherence to the MIND diet was associated with approximately a 17% lower risk of dementia compared with the lowest levels of adherence. A particularly noteworthy aspect of this study was that the components most strongly contributing to this association included leafy greens, berries, olive oil, and nuts, which are rich in polyphenols and unsaturated lipids (8).Finally, the central issue may not be the diet as a label, but rather the biochemical pattern it embodies. Dietary patterns such as MIND and the Mediterranean diet may be understood as complex biochemical arrangements that simultaneously engage multiple pathways, and in multifactorial diseases such as Alzheimer's disease, multicomponent interventions may be better aligned with the condition's multifactorial nature.Although observational effects are mild and do not establish a definitive causal link, the epidemiological clues are more consistent and replicated at a small scale than the clinical evidence currently available for the ketogenic diet.In other words, while the ketogenic diet demonstrates strong bioenergetic coherence, patterns such as the Mediterranean and MIND diets appear to act across multiple pathophysiological axes, with greater safety and broader population applicability due to cultural compatibility and cost. It is reasonable to note that, from a public health and primary prevention perspective, a dietary strategy based on plant diversity and bioactive compounds represents a sustainable, biologically more coherent, and more reasonable approach than highly restrictive interventions supported by stillinsufficient clinical evidence.A rarely emphasized issue concerns the window of opportunity for exposure to interventions. Most clinical trials and cohorts evaluate individuals aged 60 or older, a stage at which neuropathological processes and chronic neuroinflammation are usually already established. Considering that Alzheimer's disease has a prolonged preclinical phase, it is assumed that nutritional intervention is more effective as a strategy for preserving homeostasis than as a tool for reversing neurodegeneration. As pointed by the Lancet Commission (2024), modifying risk factors in middle age-such as controlling LDL cholesterol and hypertension-has significantly greater preventive potential, since diet appears to act more efficiently in preventing damage than in structurally modifying an already advanced condition (36). In this context, dietary patterns rich in vegetables, fiber, and polyphenols demonstrate a conceptual advantage: they are compatible with lifelong adoption, allowing vascular, metabolic, and inflammatory disturbances to be resolved from midlife onward, which may be more relevant than intensive interventions introduced at later stages. This does not suggest that the ketogenic diet should be abandoned as a research area. It may have a role as a periodic or intermittent ketosis strategy rather than a chronic strict dietary protocol, a hypothesis that deserves further investigation in future clinical trials; however, current evidence remains insufficient to support its routine recommendation, at least, for mitigation and/or treatment of Alzheimer's disease.
Source: Frontiers in Nutrition
Authors: Guilherme Mengue Christimann, José Augusto Gasparotto Sattler, João Paulo Fabi
Institution: Universidade de São Paulo
Language: English
Topic: Nutritional Studies and Diet
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,801
OpenAlex ID: W7154472256