How effective is HMB for muscle growth?

Does HMB supplementation result in incredible muscle mass gains?

Protein ingestion can help improve muscle mass gains during resistance training. Protein consists out of amino acids, of which leucine is the most potent to stimulate muscle protein synthesis (the process that drives muscle growth). Ingested leucine is partly metabolized into HMB. However, HMB can also be produced as a supplement.

Some previous research has reported that supplemental HMB resulted in ~5 times greater muscle mass gains than you typically see in similar protein/amino acid supplementation studies. However, these findings have been questioned by some of the leading muscle and protein researchers.

This study investigated the impact of HMB or leucine supplementation on muscle growth during a 12-week resistance training program. Importantly, the study design was very similar to the previous studies that claimed exceptionally large increases in muscle mass gains with HMB.

HMB did not increase muscle mass gains more than leucine. Both groups only had a 2-3 kg increase in lean mass, which is much less than the 7-9 kg that was previously reported for HMB.

Therefore, HMB does not seem to be an exceptional supplement that increases muscle mass gains to extraordinary levels. In general, be skeptical about supplement research that looks too good to be true. Wait until it is replicated by multiple researchers with good reputations.

Study:
Jakubowski et al. Equivalent Hypertrophy and Strength Gains in β-Hydroxy-β-Methylbutyrate- Or Leucine-supplemented Men. Med Sci Sports Exerc, 2019

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