Hydroxybutyrat

Hydroxybutyrat, more commonly referred to in English as beta-hydroxybutyrate (BHB), is a hydroxy-substituted short-chain fatty acid that functions as a ketone body in human metabolism. In physiological contexts it exists mainly as the D-enantiomer, with the L-enantiomer present in much smaller amounts. Beta-hydroxybutyrate is water-soluble and circulates in the bloodstream, where it can cross cell membranes via monocarboxylate transporters.

Beta-hydroxybutyrate is produced primarily in the liver during periods of low carbohydrate availability, such as fasting, prolonged exercise, or adherence to a ketogenic diet. It is generated from fatty acids through mitochondrial ketogenesis and serves as an important alternative energy source when glucose is scarce. Once in peripheral tissues, BHB is converted back to acetyl-CoA and enters the citric acid cycle to generate ATP. The brain and heart can utilize BHB efficiently, particularly during prolonged fasting or carbohydrate restriction.

Clinically, beta-hydroxybutyrate is used as a biomarker of ketosis and is the dominant ketone body measured in diabetic ketoacidosis, where its levels rise disproportionately relative to other ketone bodies. Blood BHB concentrations are determined by enzymatic assays or chromatographic methods and inform treatment decisions in metabolic emergencies as well as in monitoring ketogenic therapies.

In nutrition and research, exogenous ketone supplements containing beta-hydroxybutyrate salts or esters are used to elevate blood ketone levels independent of fasting. These agents are studied for potential effects on energy metabolism, cognition, and athletic performance, though evidence varies across indications.