title: Stimulation of mild, sustained ketonemia by medium-chain triacylglycerols in healthy humans: estimated potential contribution to brain energy metabolism.
abstract: OBJECTIVE
  In humans consuming a normal diet, we investigated 1) the capacity of a medium-chain triacylglycerol (MCT) supplement to stimulate and sustain ketonemia, 2) ¹³C-β-hydroxybutyrate and ¹³C-trioctanoate metabolism, and 3) the theoretical contribution of the degree of ketonemia achieved to brain energy metabolism.
  
  
  METHODS
  Eight healthy adults (26 ± 1 y old) were given an MCT supplement for 4 wk (4 times/d; total of 20 g/d for 1 wk followed by 30 g/d for 3 wk). Ketones, glucose, triacylglycerols, cholesterol, free fatty acids, and insulin were measured over 8 h during two separate metabolic study days before and after MCT supplementation. Using isotope ratio mass spectroscopy, ¹³C-D-β-hydroxybutyrate and ¹³C-trioctanoate β-oxidation to ¹³CO₂ was measured over 12 h on the pre- and post-MCT metabolic study days.
  
  
  RESULTS
  On the post-MCT metabolic study day, plasma ketones (β-hydroxybutyrate plus acetoacetate) peaked at 476 μM, with a mean value throughout the study day of 290 μM. Post-MCT, ¹³C-trioctanoate β-oxidation was significantly lower 1 to 8 h later but higher 10 to 12 h later. MCT supplementation did not significantly alter ¹³C-D-β-hydroxybutyrate oxidation.
  
  
  CONCLUSIONS
  This MCT supplementation protocol was mildly and safely ketogenic and had no side effects in healthy humans on their regular diet. This degree of ketonemia is estimated to contribute up to 8% to 9% of brain energy metabolism.
authors.affiliation: Research Center on Aging, Health and Social Services Center, University Institute of Geriatrics of Sherbrooke, Sherbrooke, Québec, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Courchesne-Loyer
authors.forename: Mélanie
authors.initials: M
authors.lastname: Fortier
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tremblay-Mercier
authors.forename: Raphaël
authors.initials: R
authors.lastname: Chouinard-Watkins
authors.forename: Maggie
authors.initials: M
authors.lastname: Roy
authors.forename: Scott
authors.initials: S
authors.lastname: Nugent
authors.forename: Christian-Alexandre
authors.initials: CA
authors.lastname: Castellano
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Cunnane
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood / Q000378:metabolism; D000090:Acetoacetates / Q000097:blood / Q000378:metabolism; D000328:Adult; D001921:Brain / Q000378:metabolism*; D002210:Caprylates / Q000378:metabolism; D002247:Carbon Isotopes; D055423:Diet, Ketogenic / Q000009:adverse effects / Q000379:methods*; D019587:Dietary Supplements / Q000009:adverse effects; D004655:Emulsions; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007662:Ketosis / Q000097:blood / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008970:Molecular Weight; D009474:Neurons / Q000378:metabolism*; D018697:Nootropic Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D012720:Severity of Illness Index; D014280:Triglycerides / Q000008:administration & dosage / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000090:Acetoacetates; D002210:Caprylates; D002247:Carbon Isotopes; D004655:Emulsions; D018697:Nootropic Agents; D014280:Triglycerides; C016635:acetoacetic acid; C003637:tricaprylin; D020155:3-Hydroxybutyric Acid