β-HYDROXY-β-METHYLBUTYRATE AS A DIETARY SUPPLEMENT (I): METABOLISM AND TOXICITY

Introduction: beta-hydroxy-beta-methylbutyrate (HMB) is a leucine metabolite produced from a-ketoisocaproic acid. HME 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. Aims: 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. Conclusion: Metabolic effects and lack of toxicity of HMB make it an adequate compound to be used as a dietary supplement.