HMB
Beta-Hydroxy Beta-Methylbutyrate
HMB (Beta-Hydroxy Beta-Methylbutyrate) is a metabolite of the essential amino acid leucine, produced naturally in the body in small amounts and available as a dietary supplement. It is primarily used to reduce exercise-induced muscle damage, attenuate muscle protein breakdown (anti-catabolic effect), and support lean muscle mass preservation, particularly in untrained individuals, older adults, and those in caloric deficits. Research supports modest benefits in muscle recovery and strength gains, especially in populations new to resistance training or experiencing muscle wasting conditions.
Mechanism of Action
HMB inhibits the ubiquitin-proteasome proteolytic pathway, which is a primary mechanism of muscle protein degradation, thereby reducing muscle catabolism during stress, illness, or intense exercise. It also appears to stimulate muscle protein synthesis by activating the mTOR (mechanistic target of rapamycin) signaling pathway and may upregulate IGF-1 expression in muscle tissue. Additionally, HMB has been shown to stabilize sarcolemmal membranes and reduce markers of muscle damage such as creatine kinase and lactate dehydrogenase following intense exercise.
Evidence by Health Goal(15 goals)
Dosing Protocols
With meals or approximately 30-60 minutes before exercise on training days
The 3g/day total dose is the most studied and consistently effective dose in clinical literature. Splitting into three 1g doses improves absorption and maintains steadier plasma levels. The free acid form (HMB-FA) may achieve faster peak plasma concentrations than the calcium salt form (Ca-HMB), but both appear similarly effective over time.
Safety & Side Effects
HMB has a well-established safety profile with no serious adverse events reported in clinical trials using standard doses of 3g/day for up to 12 months. It is considered safe for most healthy adults and older populations, though individuals with liver or kidney disease should consult a physician before use.
Possible Side Effects
- !Mild gastrointestinal discomfort (nausea, bloating) especially with calcium salt form at higher doses
- !Loose stools or mild diarrhea when initiating supplementation
- !Elevated LDL cholesterol reported in some studies at high doses
- !Transient increases in liver enzymes (ALT/AST) observed in isolated cases
- !Headache reported rarely in clinical trials
- !Potential mild hypotensive effect in susceptible individuals
Interactions
- -May have additive anti-catabolic effects when combined with leucine or BCAAs, potentially reducing required doses of each
- -May modestly enhance the effects of creatine monohydrate on strength and lean mass when co-administered
- -Use caution with cholesterol-lowering statins - HMB may theoretically affect the mevalonate pathway similarly to statins, though clinical significance is unclear
- -May have additive blood pressure-lowering effects when combined with antihypertensive medications - monitor blood pressure
- -Combined use with anabolic hormones (testosterone, GH) may produce synergistic lean mass effects, but clinical interaction data is limited
Cost & Where to Buy
Cost varies by form (calcium salt vs. free acid) and brand. Ca-HMB powder is the most affordable option; branded free acid formulations (e.g., BetaTOR) carry a significant price premium. Bulk powder from reputable suppliers represents the best value.
Search on Amazon