Acute Effects of D- and L-Beta-Hydroxybutyrate on Vigilance (Sustained Attention and Reaction Speed) in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Acute Effects of D- and L-Beta-Hydroxybutyrate on Vigilance (Sustained Attention and Reaction Speed) in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Alvin Sherman Library

Exogenous beta-hydroxybutyrate (BHB) supplements are increasingly promoted for cognitive and performance benefits but controlled human data--particularly comparing BHB isomers--remains sparse. This study evaluated whether a low dose, acute ingestion of D-BHB or L-BHB influences vigilance (sustained attention, reaction speed) and fine motor control in fasted, non-keto-adapted healthy adults. A total of 136 participants (20.5 ± 1.4 years; 70.2 ± 15.6 kg) were randomized into three groups: D-BHB (n = 47), L-BHB (n=46), or placebo (n = 43). Measures included the Psychomotor Vigilance Test (PVT reaction time) and the central nervous system tap test. Assessments were conducted at baseline and 60 minutes post-consumption. Data were analyzed using a two-way ANOVA with post hoc Tukey tests where appropriate. An exploratory analysis was also conducted to assess within-group changes over time and to estimate effect sizes. A significant group effect was found for reaction time (p = 0.033). Group B (L-BHB) performed significantly faster than placebo (p = 0.029). No time or interaction effects were noted. Lapse counts were higher in the placebo group compared to both BHB groups (p = 0.004). The ANOVA did not show a significant group x time interaction. The main study effect was that both BHB groups (D- and L-) had fewer lapses overall than placebo, across all time points. In the absence of significant time effects (all p > .05), exploratory analyses were conducted to assess within-group changes over time and to estimate effect sizes. Although the ANOVA did not identify statistically significant effects, within-group paired t-tests and effect size, estimates were computed to explore potential patterns. These small effect sizes (Group A: 0.264; Group B: 0.271) suggest small changes within Group A and Group B between the pre- and post 60-minute time points. The findings indicate that acute BHB ingestion--particularly L-BHB--improves reaction speed and reduces attentional lapses compared to placebo, even at low doses, supporting the need for further dose-response and mechanistic research.