Calcium β-hydroxy β-methylbutyrate (HMB)

Primary uses

• Muscle protein synthesis enhancement
• Attenuation of muscle protein breakdown
• Resistance training recovery support
• Age-related muscle loss (sarcopenia) management
• Athletic performance and strength gains

How it works

• Activates mTOR signaling pathway to promote muscle protein synthesis
• Inhibits proteasome and calpain-mediated muscle protein degradation
• Reduces inflammation and oxidative stress markers in muscle tissue
• May increase satellite cell activation for muscle fiber repair

Dosage

Typical range

3,000–3,600 mg daily (divided into 2–3 doses, typically 1,000–1,200 mg per dose)

Timing

Distribute across meals; post-workout timing may offer marginal additional benefit when combined with resistance training

With food

With meals; may improve absorption and reduce GI upset

Duration

Effects typically emerge after 2–4 weeks of consistent supplementation. Long-term safety data support use for 12+ weeks. Discontinuation leads to gradual return to baseline within 2–4 weeks.

Special populations

Greatest benefit in older adults (65+), untrained individuals, and those recovering from illness or immobility. Benefits are additive to resistance training; minimal effect without exercise stimulus.

Forms

• Calcium HMB monohydrate· 70/100
• Free-acid HMB· 70/100
• Capsule· 70/100
• Tablet· 70/100
• Powder· 70/100

Safety

Common side effects

• Generally well-tolerated
• Mild GI upset (nausea, diarrhea) at high single doses; mitigated by dividing doses
• Occasional headache or dizziness reported (rare)

Contraindications

• No absolute contraindications at recommended doses
• Individuals with severe renal impairment should monitor metabolite levels (consult provider)

Evidence notes

Good-quality RCT evidence in resistance-trained and aging populations supports modest improvements in lean mass and strength. Effects are most pronounced in untrained individuals and older adults; benefits in trained athletes are smaller but consistent. Standard dose is 3 g/day.

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

Related in Amino Acid

• Whey Protein IsolateA
• Calcium β-hydroxy β-methylbutyrate monohydrateB
• Hydrolyzed Whey ProteinA
• L CarnitineB
• L-Citrulline Malate (2:1)B
• L-Ornithine HydrochlorideC