The newborns are not created equal. Maturity levels determine energy substrate use

Stereoisomers of beta-hydroxybutyrate: what works, what doesn't

D-beta-Hydroxybutyrate is a physiologically occurring D-isomer produced by hepatocytes and, to a lesser extent, by astrocytes. It is an alternative source of energy in the brain when glucose supply is depleted

The vast majority of researchers dealing with effects of ketone bodies or, specifically, beta-hydroxybutyrate, use the mixture of D and L isomers, the racemate DL-beta-hydroxybutyrate since the L-form is essentially inactive and, correcting for the actual dosage of D-form in the racemate, effects are safely attributed to the active D-form.

Biological effects of DL-form are abundant in many species, organs, preparations, and conditions. Did I mention that DL form is substantially cheaper than the pure isomers?

An interesting reason can be added to the advantages of using racemate of beta-hydroxybutyrate. It turns out that in the process of separation of the isomers, a non-physiological contaminant, dibenzylamine, remains with the L-form changing it from biologically inactive to biologically VERY active. When left alone, the DL form remained free of dibenzylamine. It's a good news because we can rest assured that the many effects of DL-beta-hydroxybutyrate remain reliable.

Source: Jong M. Rho, Gail D. Anderson, Sean D. Donevan, and Steve White. Acetoacetate, Acetone, and Dibenzylamine (a Contaminant in L-(+)-b-Hydroxybutyrate) Exhibit Direct Anticonvulsant Actions in Vivo. Epilepsia, 43(4):358-361, 2002