Leucine is found in high concentrations in muscles. During athletic training as muscles are damaged, leucine is broken down and the concentration of both leucine and HMB in muscle increases. It is therefore possible that giving extra HMB may work in the reverse way, slowing the breakdown of leucine in the muscle.

Natural Sources: HMB is present in small amounts in Alfalfa, Asparagus, Avocado, Cauliflower, Catfish, Grapefruit, and Red Meats.

Useful in treatment of: Athletics and Sports. HMB appears to also increase the growth of lean muscle tissue.¹ Athletes using the supplement have shown more muscle gain than those not taking the supplement over a comparable time period under the same exercise regimen, as well as increased strength.² However, the study was not blinded, which may have affected results.

Recommended Dosage: Studies have been done using from 0.5 to 3 grams per day. Doses up to 4 grams per day have been used without side effects.

Contraindications: There are no known contraindications to HMB, but formal safety studies have not been established.

References:

¹Nissen S, Panton L, Wilhelm R, et al. Effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation on strength and body composition of trained and untrained males undergoing intense resistance training. FASEB J 1996;10:A287 (abstract).
²Nissen S, Sharp R, Ray M, et al. Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistive-exercise training. J Appl Phys 1996;81:2095–104.