Abstract
Beta-hydroxybutyrate (D-BHB) is a metabolite with intrinsic signalling activity that has gained attention as a potentially clinically useful supplement. There are available supplements for inducing ketosis: ketone salts, ketone esters and medium-chain triglycerides. Even when all of them raise D-BHB in the blood and all are safe and well tolerated, they significantly differ in their safety profile, their palatability and their price. A fourth and potentially interesting option is to use biologically identical D-BHB, which it is already commercially available in the USA (American Ketone) and Greater China (MedPHA). However, its safety and tolerability had not yet been documented in the scientific literature. We evaluated the safety and tolerability of orally administered free D-BHB in a gender and age-balanced sample of 24 asymptomatic and overtly healthy adults. No participant showed acid-base abnormalities or electrolyte abnormalities. Secondary symptoms were reported after only 6.2% of all drink takes and none of the reports described the symptom as 'severe'. The most frequently reported secondary effects (19/720 or 2.6%) were gastrointestinal discomfort, headache (7/720 or 1%) and loss of appetite (7/720 or 1%). No correlation between weight-adjusted dose and frequency of secondary symptoms was observed. Free D-BHB was a safe and well-tolerated intervention for inducing sustained exogenous ketosis. Being bioidentical, salt-free and lacking intermediate metabolites, this form of supplementation could have a larger safety spectrum than salt or alcohol-based exogenous ketones. More research is warranted to assess its clinical efficacy in those clinical scenarios in which achieving ketosis rapidly could be beneficial.