Acute exogenous ketone monoester supplementation decreases indices of cardiac vagal modulation in a dose-dependent manner in healthy adults.

Exogenous ketone supplementation can elevate heart rate (HR) but the effects on cardiac autonomic modulation remain unclear. HR variability was analyzed from 18 healthy adults (23 ± 3 years; n = 10 females) ingesting 0.3 or 0.6 g/kg ketone monoester or placebo in a randomized crossover, double-blind design. Compared to placebo, both ketone doses increased plasma β-hydroxybutyrate and reduced the percentage of successive R-R intervals that differ by ≥50 ms (pRR50) and the root mean square of successive differences (RMSSD) at 45 min (both p < 0.02) and 120 min post-ingestion (both p < 0.01). Acute ketone ingestion decreases HR variability measures associated with cardiac vagal modulation.