Acute Supplementation of Beta-Hydroxybutyrate Increases Visual Cortical Excitability in Humans: A Combined Electro-EncephaloGraphy and Magnetic Resonance Spectroscopy Study.

Increasing plasma levels of ketone bodies via supplementation has been recently found to modulate the neurometabolic profile in the healthy human brain. Here, we aimed to explore the physiological consequences of these neurometabolic changes by assessing visual cortical function. Ten young adult human volunteers (mean age 27 years, range 23-34) were orally administered a single dose of a β-hydroxybutyrate (βHB) ester (one of the main ketone bodies), and we measured neurometabolic change after supplementation. We used Electroencephalography (EEG) to assess cortical responsivity to visual stimuli and endogenous rhythms, and magnetic resonance spectroscopy (MRS) to quantify glutamate and GABA+ concentrations in the occipital cortex. βHB supplementation increased the amplitude of steady-state visual evoked potentials and increased resting-state EEG alpha power (8-13 Hz). These electrophysiological changes were paralleled by an increase in glutamate (but not GABA+) concentration in the occipital cortex. The glutamate increase was correlated with the increased steady-state visual evoked potentials amplitude. This suggests that acute βHB supplementation increases the excitability of the brain cortex, as assessed neurometabolically and electrophysiologically. We discuss how these effects of acute supplementation may differ from the long-term effects of chronic interventions in healthy or pathological brains.