title: [β-hydroxy-β-methylbutyrate as a dietary supplement (I): metabolism and toxicity].
abstract: BACKGROUND
  -hydroxy--methylbutyrate (HMB) is a leucine metabolite produced from -ketoisocaproic acid. HMB supplementation has been used as a dietary supplement in sports since 1997, with the aim of decreasing muscle proteolysis. In recent years, positive effects have been reported in different pathologies, which suggests potential health benefits.
  
  
  OBJECTIVE
  The objectives of this review are: to know both HMB metabolism and toxicity, and to identify HMB cellular and molecular mechanisms of action when used as a dietary supplement.
  
  
  METHODS
  A search was performed in the Web of Science, Pubmed and SportDiscus data bases. RESULTS were divided into two parts; this article presents the results about both HMB metabolism and possible toxicity.
  
  
  RESULTS
  Studies show that HMB is related to cholesterol metabolism in skeletal muscle, which could reduce proteolysis, through hydroxy-methyl-glutaryl-coenzyme A and mevalonate as a precursor in the synthesis of cholesterol. However, HMB could also be transformed from acetoacetate to beta-hydroxybutyrate by beta-hydrozybutyrate dehydrogenase. The calcium salt of HMB is the most used chemical form in dietary supplements, being the most common dose 3 g of HMB/day. Studies in humans and animals provide evidence that there are no adverse effects associated with HMB supplementation.
  
  
  CONCLUSIONS
  Metabolic effects and lack of toxicity of HMB make it an adequate compound to be used as a dietary supplement.
authors.affiliation: Licenciatura en Cultura Física y Deporte, Facultad de Ciencias de la Conducta, Universidad Autónoma del Estado de México (UAEMex). Toluca, México. Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Rafael
authors.initials: R
authors.lastname: Manjarrez-Montes-de-Oca
authors.affiliation: Licenciatura en Biología, Facultad de Ciencias, UAEMex. Toluca, México.. ialvor@unileon.es.
authors.forename: Mateo
authors.initials: M
authors.lastname: Torres-Vaca
authors.affiliation: Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Javier
authors.initials: J
authors.lastname: González-Gallego
authors.affiliation: Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Ildefonso
authors.initials: I
authors.lastname: Alvear-Ordenes
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D019587:Dietary Supplements; D006801:Humans; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D014631:Valerates / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000633:toxicity*
chemical_list: D014631:Valerates; C004961:beta-hydroxyisovaleric acid; D002784:Cholesterol