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Amino Acid

Calcium β-hydroxy β-methylbutyrate monohydrate

Also known as: HMB, β-hydroxy β-methylbutyrate, beta-hydroxy beta-methylbutyrate, calcium HMB

B
Evidence

HMB is a metabolite of the branched-chain amino acid leucine that may support muscle protein synthesis and reduce muscle breakdown during resistance training and caloric restriction. Research shows modest benefits for lean mass retention and strength gains, particularly in untrained or aging populations.

Primary uses

  • Muscle protein synthesis support
  • Lean mass preservation
  • Strength and power development
  • Recovery from resistance training
  • Age-related muscle loss (sarcopenia)

How it works

  • Inhibits protein degradation pathways (ubiquitin-proteasome system)
  • Activates mTOR signaling for anabolic responses
  • Modulates myostatin expression
  • Reduces exercise-induced muscle damage markers

Dosage

Typical range
1.5-3 grams daily (divided into 2-3 doses)
Timing
Distributed throughout the day; around workouts may be optimal
With food
May be taken with or without food; consistency more important than timing
Duration
Benefits typically emerge after 2-4 weeks of consistent use; optimal duration unclear but studies extend to 12+ weeks
Special populations
Appears safe and potentially beneficial for older adults and untrained individuals; limited evidence in elite/highly trained athletes

Forms

  • Calcium HMB monohydrate capsules· 70/100
  • Calcium HMB powder· 70/100
  • Free acid HMB· 70/100

Safety

Common side effects

  • Generally well-tolerated
  • Rare reports of nausea or stomach upset at high doses

Contraindications

  • No major contraindications identified
  • Caution in individuals with severe kidney disease (metabolite clearance)

Evidence notes

Moderate evidence from multiple RCTs showing modest lean mass and strength gains in resistance-trained individuals, untrained persons, and aging populations. Effect sizes are generally small to moderate. Most robust evidence exists for untrained individuals and older adults; benefits in elite athletes less clear.

Grade B: Some human trials support key claims; further confirmation needed.

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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider.