Evidence B · Good
Water-soluble
Chronic (2+ wk)
A metabolite of leucine (~5% of leucine is converted to HMB). It reduces muscle protein breakdown by inhibiting the ubiquitin-proteasome system and stabilizes the cell membrane. The effect is most relevant in high-stress contexts: caloric deficit, high training volumes, and injury-recovery phases.
Total dose3 g/day (split into 3×)
HMB-Ca (calcium)60–90 min pre-workout
HMB-FA (free acid)30–60 min pre-workout
FoodIndependent
Why it's strategic for ultramarathon runners
- High volume + caloric deficit: the classic combination for anyone cutting weight before a race triggers muscle catabolism. HMB counteracts this.
- Reduces CK and LDH after long, eccentric sessions (technical descents).
- Speeds up recovery between sessions during peak-volume weeks.
- Preserves lean mass during a "cut" (when you're going from 86 kg down to 82 kg).
HMB-Ca vs. HMB-FA
| Characteristic | HMB-Ca (calcium) | HMB-FA (free acid) |
|---|---|---|
| Plasma peak | ~120 min | ~30 min |
| Pre-workout timing | 60–90 min before | 30–60 min before |
| Availability | Widely available | Limited |
| Cost | $ (cheaper) | $$$ (premium) |
| Stability | High (capsule) | Lower (liquid) |
Practical protocol (3g/day)
- Dose 1: 1g before breakfast (or together if your stomach is sensitive).
- Dose 2: 1g 60–90 min before training (critical timing — the anti-catabolic window).
- Dose 3: 1g with dinner.
- On non-training days, 3 doses throughout the day (morning, lunch, dinner).
When the effect is greater
- Beginners or untrained individuals (large effect).
- Moderate-to-severe caloric deficit (large effect).
- Very high training volumes (moderate effect).
- Endurance athletes in peak phases (moderate effect on CK/LDH).
When the effect is smaller
- Advanced athlete in maintenance, with well-calibrated nutrition — the effect is small.
- In a caloric surplus — other strategies (protein + creatine) already saturate the gains.
💡 Synergy: HMB + Creatine + Whey is the best-studied "anti-catabolic tripod". The three act on different pathways (HMB inhibits breakdown, creatine increases ATP synthesis, whey supplies leucine/amino acids).
Safety
Exceptional. Doses of up to 6g/day are well tolerated in long-term studies. No clinically relevant adverse effects. Not banned by WADA.
Product in use: Growth Supplements HMB
HMB by Growth Supplements is the most affordable Brazilian option. 90 capsules with HMB-Ca (calcium HMB) — the standard form.
- Label dosage: 3 capsules/day (~333 mg HMB per capsule × 3 = 1 g HMB/day)
- Bottle lasts: 30 days at the label dose
- Average price: R$46,90 (ranges R$37–62 across stores)
- Cost/day (label): R$1,55
⚠️ ANVISA caps it at 3g/day but the product label carries the conservative recommendation (1g/day, within the "1g per 25kg" limit). To reach the scientific target of 3g/day (based on international RCTs), you would need 9 capsules/day — the bottle lasts ~10 days, cost ~R$4,69/day. For most users, 1g already provides a significant benefit, especially in a caloric deficit.