Beetahydroksibutyraatti

Beetahydroksibutyraatti, known in English as beta-hydroxybutyrate (BHB), is one of the ketone bodies produced during fatty acid oxidation. It exists as two enantiomers, D- and L-. The D-enantiomer is the form most involved in energy metabolism in mammals, while the L-enantiomer is less commonly used by human tissues.

In mammals, the liver generates acetoacetate and D-beta-hydroxybutyrate from fatty acids during fasting or carbohydrate restriction. These ketone bodies are released into the bloodstream and transported to tissues such as the brain, heart, and skeletal muscle, where they are converted to acetyl-CoA and enter the citric acid cycle. The liver itself lacks the enzyme succinyl-CoA:3-ketoacid transferase (SCOT) and therefore does not efficiently use ketone bodies for energy.

Physiological role: Ketone bodies provide an alternative energy source when glucose availability is limited. D-BHB readily crosses the blood–brain barrier and can support brain energy metabolism during prolonged fasting or ketosis. Clinically, elevated ketone levels are a feature of diabetic ketoacidosis; exogenous BHB supplementation is studied for potential benefits in epilepsy, metabolic disorders, and neurodegenerative diseases, though evidence is mixed.

Forms and safety: BHB used as a supplement is typically provided as mineral salts (sodium, potassium, calcium) or as esters. Exogenous BHB raises blood ketone levels but may cause gastrointestinal discomfort or electrolyte imbalance in some users. It should be used with caution in people with diabetes, kidney disease, or those taking certain medications. See also: ketone bodies, ketogenic diet.