MCT Oil — The Ketogenic Brain Fuel
Medium-chain triglycerides (MCTs) are fatty acids with 6–12 carbon chains (C6 caproic, C8 caprylic, C10 capric, C12 lauric) that are metabolised differently from long-chain fats. Unlike LCTs, MCTs are absorbed directly into the portal circulation, bypass lymphatic transport, and are rapidly converted to ketones in the liver — providing an alternative fuel for the brain that doesn't require insulin. C8 (caprylic acid) is the most ketogenic MCT.
Mechanism of Action
MCTs are transported directly to the liver via the portal vein, where they undergo rapid beta-oxidation and ketogenesis (producing beta-hydroxybutyrate and acetoacetate). Ketones cross the blood-brain barrier and are preferentially used by neurons, providing an alternative to glucose. This is particularly relevant in Alzheimer's disease, where glucose metabolism is impaired. MCTs also activate AMPK and PPARα, promoting fat oxidation and mitochondrial biogenesis.
Human Trial Evidence
A 2004 Neurobiology of Aging RCT showed MCT supplementation (40 mL/day) significantly improved cognitive performance in Alzheimer's patients with APOE ε4-negative genotype. A 2018 Frontiers in Molecular Neuroscience RCT confirmed cognitive benefits. Multiple RCTs show MCTs increase ketone levels, reduce appetite, and support weight management. Evidence for longevity is primarily mechanistic.
Dosing Protocol
1–4 tablespoons (15–60 mL) per day of C8-rich MCT oil. Start with 1 tsp/day and increase gradually to avoid GI distress. Best added to coffee, smoothies, or salad dressings. C8 (caprylic acid) is the most ketogenic — choose MCT oil with >50% C8. Avoid heating to high temperatures (smoke point ~160°C).
Safety & Contraindications
Well-tolerated at moderate doses. GI distress (nausea, diarrhoea, cramping) is the primary side effect — dose-dependent. Start low and titrate. May raise LDL cholesterol with high intake. Avoid in liver disease (rapid hepatic metabolism may overwhelm liver). Not suitable for those with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.