The cognitive function of dogs diminishes over time and may serve as an animal model for cognitive decreases associated with human aging. Declines in accessible energy sources as well as decreased brain glucose may be physiologic causes for such cognitive decreases. Ketones could serve as an alternative natural energy source; they are produced in the body by the liver and kidney by fat breakdown and can be used as an energy source by the brain. Medium-chain triacylglycerols (MCTs) can increase concentrations of brain ketones to provide neurons with additional energy sources in the presence of decreased brain glucose. Two test protocols were performed in this study to assess general cognitive function: (1) learning ability, visuospatial function, and a landmark discrimination learning protocol and (2) egocentric spatial ability. Baseline cognitive testing was performed on aged beagle dogs (N = 24) to establish cognitively equivalent
control (n = 12 [6 females, 6 males]) or test diet (n = 12 [8 females, 4 males]) groups; baseline test results did not differ between groups. Dogs were given a control or test (5.5% MCT) diet for 8 months. Cognitive function of the dogs was tested by using several cognitive testing protocols that assessed landmark discrimination ability, egocentric visuo-spatial function, and attention. The MCT-supplemented group had significantly elevated levels of the ketone body beta-hydroxybutyrate and performed the landmark test more accurately than control dogs. These results collectively suggested that MCT supplementation may improve cognition and will increase circulating ketone levels.

Commentary: Future prospective studies could evaluate cognitive function in different dog breeds over extended periods and compare the clinical benefits of MCT supplementation in these geriatric patients. Evaluations of the contributory effects of dog breed and sex on cognitive function are also necessary. Large, multicenter prospective studies could include client-owned dogs, resulting in larger sample sizes, more robust data, and evaluation of potential side effects of ketone metabolism.

Dietary supplementation with medium-chain TAG has long-lasting cognition-enhancing effects in aged dogs. Pan Y, Larson B, Araujo JA, et al. BR J NUTR 103:1746-1754, 2010.