• E Freemantle, M Vandal, J Tremblay Mercier, M Plourde, J Poirier, and S C Cunnane.
• Research Center on Aging, Health, and Social Services Center, Sherbrooke University Geriatrics Institute, 1036 Belvédère S., Sherbrooke, QC, Canada.
• J Nutr Health Aging. 2009 Apr 1; 13 (4): 293-8.

ObjectiveTo determine whether the metabolism of glucose or ketones differs in the healthy elderly compared to young or middle-aged adults during mild, short-term ketosis induced by a ketogenic breakfast.Design And ParticipantsHealthy subjects in three age groups (23 +/- 1, 50 +/- 1 and 76 +/- 2 y old) were given a ketogenic meal and plasma beta -hydroxybutyrate, glucose, insulin, triacylglycerols, total cholesterol, non-esterified fatty acids and breath acetone were measured over the subsequent 6 h. Each subject completed the protocol twice in order to determine the oxidation of a tracer dose of both carbon-13 (13C) glucose and 13C-beta-hydroxybutyrate. The tracers were given separately in random order. Apolipoprotein E genotype was also determined in all subjects.ResultsPlasma glucose decreased and beta-hydroxybutyrate, acetone and insulin increased similarly over 6 h in all three groups after the ketogenic meal. There was no significant change in cholesterol, triacylglycerols or non-esterified fatty acids over the 6 h. 13C-glucose and 13C-beta-hydroxybutyrate oxidation peaked at 2-3 h postdose for all age groups. Cumulative 13C-glucose oxidation over 24 h was significantly higher in the elderly but only versus the middle-aged group. There was no difference in cumulative 13C-beta-hydroxybutyrate oxidation between the three groups. Apolipoprotein E (epsilon 4) was associated with elevated fasting cholesterol but was unrelated to the other plasma metabolites.ConclusionElderly people in relatively good health have a similar capacity to produce ketones and to oxidize 13C-beta-hydroxybutyrate as middle-aged or young adults, but oxidize 13C-glucose a little more rapidly than healthy middle-aged adults.

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