Abstract
- Background
It is now widely accepted that ketosis—a physiological state characterized by elevated plasma ketone body levels—possesses a broad spectrum of neuroprotective and neuromodulatory effects. Consequently, there is a rapidly growing clinical and scientific interest in utilizing exogenous ketogenic supplements, particularly medium-chain triglycerides (MCTs), as a practical dietary strategy to achieve intermittent nutritional ketosis without requiring strict adherence to highly restrictive ketogenic diets. MCT supplementation represents an inexpensive, simple, and accessible ketogenic intervention that has demonstrated clinical promise in benefiting both healthy individuals with normal cognition and patients suffering from mild cognitive impairment (MCI), Alzheimer's disease (AD), and other neurodegenerative cognitive disorders. The conventionally accepted paradigm underlying clinical trials of MCT supplementation posits that procognitive benefits stem primarily from hepatic ketogenesis and subsequent cerebral utilization of ketone bodies. However, medium-chain fatty acids (MCFAs) may also exert direct, independent physiological and cellular effects within the central nervous system. Furthermore, MCFAs, long-chain fatty acids, and systemic glucose participate in mutually intertwined, highly complex metabolic pathways. Therefore, comprehensive metabolic interactions must be carefully considered, particularly when therapeutic procognitive protocols require administering MCTs in dosages exceeding $1\text{ g/kg}$. This review summarizes currently available research regarding the procognitive effects of utilizing MCTs as a dietary supplement to regular diets without concomitant carbohydrate restriction, focusing on revealed mechanisms linked to specific MCT metabolites (such as ketone bodies and MCFAs) while highlighting critical open questions and potential clinical considerations.
- Methods
A comprehensive narrative literature review was conducted across major electronic scientific databases—including PubMed, Scopus, Embase, and Web of Science—focusing on peer-reviewed preclinical animal models, human clinical trials, randomized controlled trials (RCTs), and mechanistic reviews evaluating the procognitive and metabolic impacts of medium-chain triglyceride supplementation. Data extraction and critical synthesis prioritized examining:
Physicochemical & Metabolic Pathways: Absorption kinetics of medium-chain fatty acids (caprylic [C8] and capric [C10] acids), hepatic $\beta$-oxidation rates, and systemic ketogenesis.
Direct vs. Indirect Central Nervous System Effects: Differentiating the neurobiological impacts of circulating ketone bodies ($\beta$-hydroxybutyrate) from the direct actions of unesterified MCFAs crossing the blood-brain barrier.
Metabolic Crosstalk: The complex biochemical interactions between MCFAs, long-chain fatty acids, and cerebral glucose metabolism in aging and vulnerable brains.
Procognitive Outcomes & Dosage Thresholds: Cognitive performance metrics, memory scores, executive function changes, and safety considerations associated with high-dose MCT protocols (exceeding $1\text{ g/kg}$).
- Results
The synthesized literature reveals a multifaceted understanding of MCT supplementation beyond the traditional ketogenesis-centric paradigm:
Validation of Ketogenic & Procognitive Benefits: MCT supplementation consistently induces mild hyperketonemia, providing an alternative, highly efficient bioenergetic fuel that bypasses cerebral glucose hypometabolism in aging populations and patients with mild cognitive impairment.
Direct Neuroactive Roles of MCFAs: Beyond serving merely as ketone precursors, unesterified medium-chain fatty acids (MCFAs) can directly influence neural cell signaling, mitochondrial function, and membrane dynamics within the brain.
Intertwined Metabolic Pathways: Systemic utilization of MCTs interacts directly with ongoing carbohydrate and long-chain fatty acid metabolism, indicating that high-dose administration ($>1\text{ g/kg}$) requires careful metabolic profiling to optimize efficacy and avoid systemic interference.
Safety & Tolerability Parameters: While MCT supplementation remains a cost-effective and generally safe intervention, dosage-dependent gastrointestinal side effects must be managed through gradual titration protocols.
- Conclusions
Medium-chain triglyceride supplementation offers an effective, non-restrictive strategy to induce mild ketosis and confer significant procognitive benefits in normal aging and neurodegenerative conditions. However, optimal therapeutic translation requires looking beyond the traditional ketogenesis model to account for direct MCFA actions and complex metabolic crosstalk, particularly at higher dosage thresholds ($>1\text{ g/kg}$). Future research must address these open mechanistic questions to refine personalized nutritional neurology protocols.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9334743/