HMB is a metabolite of leucine and alpha-ketoisocaproate that has gained popularity as an ergogenic supplement for athletes.
It prevents muscle damage caused by mechanical stimuli and stimulates muscle protein synthesis.
It accelerates the recovery process post-exercise.[1] [2] [3]
Health Benefits of HMB Supplements
The key benefits of HMB supplements include increasing fat-free mass, muscle strength, power, and reducing muscle damage in untrained and trained individuals. It might increase muscle mass and decrease muscular atrophy in older adults. It may reduce muscle wasting associated with chronic conditions and lower cardiovascular risk factors.
1. HMB supplements improve markers of resistance training
Studies showed that HMB supplementation reduced markers of muscle damage, increased lean body mass gain, and strength following resistance training.[4][5] [6]
HMB supplements increase fat-free mass and muscle strength during resistance training
HMB supplements increased skeletal muscle mass and improved muscle strength during resistance training.[7] [8]
In a study involving untrained individuals, HMB supplementation increased fat-free mass and decreased plasma creatine phosphokinase activity during eight weeks of resistance training.[9] [10]
A combination of 3-10 g/day of creatine monohydrate and 3g/day of HMB increased muscle strength and anaerobic performance. It increased fat-free mass after four weeks.[11] [12]
Another study showed that HMB-FA+ATP enhanced lean body mass, power, and strength (1.3%) during the overreaching phase of exercise.[13]
What it means: HMB supplements alone or combined with creatine, ATP increased muscle strength and fat-free mass following resistance training. Additional research studies are required to examine the molecular mechanisms by which HMB supplements increased exercise performance.
2. HMB supplements reduce muscle damage
Studies showed that HMB supplements reduced exercise-induced muscle damage.[14] [15]
A study showed that HMB supplementation (1.5 or 3 g) increased fat-free mass, total strength, and prevented exercise-induced muscle damage.[16]
HMG supplementation decreased creatine phosphokinase, LDH, and prevented exercise-induced muscle damage after a prolonged run.[17]
Another study showed that a combination of HMB and alpha-ketoisocaproic acid for 14 days before exercise lowered symptoms of exercise-induced muscle damage in non-resistance trained adults.[18]
However, in one study, short term supplementation of HMB (40mg/kg body weight/day) did not reduce symptoms of eccentric muscle damage.[19]
What it means: Some studies showed that HMB supplements alone and in combination with alpha-ketoisocaproic acid prevented muscle damage during resistance training. Further studies will determine the molecular mechanisms involved in treating muscle damage by HMB supplements.
3. HMB supplements may enhance threshold and power during resistance training
HMB supplements may enhance time to reach the threshold and anaerobic peak power during resistance training.[20]
In a study involving trained athletes, 12 weeks of HMB supplementation increased time to reach the threshold, anaerobic peak power, maximum speed, and lactate concentration.[21]
A study showed that HMB supplementation increased refusal time to continue in progressive time, maximum load, and peak power.[22]
A study showed that 3g/day of HMB supplementation increased peak and mean anaerobic power during resistance training in volleyball players.[23]
What it means: Studies showed that HMB supplementation might increase anaerobic peak power and time to reach the threshold during resistance training. Further prospective studies will determine the effectiveness of HMB supplements in increasing power output during resistance training.
4. HMB supplements may increase muscle mass and decrease muscle atrophy in older adults
Studies showed that HMB supplementation might enhance muscle mass, strength, and reduce muscle atrophy in elderly subjects.[24] [25]
A randomized controlled study showed that HMB supplementation prevented the decrease in lean body mass and muscle atrophy over bed rest in healthy older adults.[26] [27] [28]
A study showed that HMB supplementation increased fat-free mass gain in elderly adults during resistance training.[29]
In a double-blind study, supplementation of HMB, arginine, and lysine improved muscle strength in women with a mean age of 76.7years. [30]
What it means: Studies have shown that HMB supplements may increase muscle mass, strength, and protein synthesis in the elderly subjects during resistance training. It may preserve muscle mass during bed rest. Additional studies are required to confirm the role of HMB supplements to treat sarcopenia.
5. HMB supplements with arginine and glutamine may lower muscle wasting in patients with AIDS and cancer
Studies showed that HMB supplements with glutamine and arginine might reduce muscle wasting, protein breakdown in cancer, and AIDS patients.[31] [32] [33]
A study showed that a combination of HMG, Arg, and Gln decreased lean tissue loss and improved immune status in AIDS patients.[34]
A combination of HMB, arginine, and glutamine improved emotional profile, increased RBCs, immune cells, and reduced muscle wasting associated with AIDS and cancer.[35]
What it means: Some studies showed that HMB supplements in combination with arginine and glutamine might reduce muscle wasting associated with AIDS and cancer. More randomized controlled studies are required to determine if HMB supplements can be used to treat cachexia.
6. HMB supplements may reduce cholesterol levels
Early studies showed that HMB supplements might reduce cardiovascular risk factors, including LDL cholesterol, total cholesterol, and blood pressure.[36]
Studies showed that HMB supplementation decreased total cholesterol and LDL cholesterol levels. It also reduced systolic blood pressure. [37]
Another study showed that short term HMB supplementation during energy restriction reduced body fat in judo athletes. However, it increased total cholesterol levels.[38]
What it means: Preliminary study showed that HMB supplementation might reduce cholesterol levels and blood pressure. However, the studies assessing the effect of HMB supplements on reducing cardiovascular risk factors are scarce and, therefore, warrants more investigation.
Precautions
Possible Side effects of HMB Supplements
HMB supplements are possibly safe when taken by mouth for a short term. Doses up to 3g per day seems to be safe.
Safety aspects
There is no reliable information about the safety of HMB supplements during pregnancy and breastfeeding. Therefore, avoid taking HMB supplements during these times.
Possible Drug Interactions with HMB
There is no well-documented interaction of HMB supplements with other drugs.[39]
Dosage
There is no adequate information about the optimal recommended dose of HMB supplements. The clinical studies used HMB in the range of 1-3g/day for reducing muscle mass loss.[40]
FAQs
HMB supplements may show anabolic (increase muscle mass) and anti-catabolic effects (decrease muscle damage). The different possible mechanisms of these supplements are inhibiting protein degradation, reducing cell apoptosis, increasing muscle protein synthesis, stimulating growth hormone/insulin-like growth factor-1, and enhancing proliferation of muscle stem cells. [41] [42] [43]. However, more studies are required to confirm the mechanisms.
Rheumatoid arthritis is an inflammatory condition that resulted in consequent muscle wasting called cachexia. A study showed that a combination of HMG, glutamine, and arginine increased fat-free mass, lean mass, and total body protein. It reversed cachexia in rheumatoid arthritis patients. [44] Further controlled studies are necessary to confirm the effects of HMB supplements in treating rheumatoid cachexia.
A study showed that 61-week oral supplementation of HMB improved the volumetric bone mineral density of the lumbar spine.[45] Another turkey study showed that HMB supplementation for long term improved vBMD and mechanical properties of the skeletal system.[46] Future additional studies are required to evaluate if HMB supplements can influence bone tissue metabolism and treat osteoporosis.
Summary
HMB, a leucine metabolite, is a supplement marketed to prevent muscle damage and increase power during resistance training in physically active and untrained adults. It is also studied for its role in increasing muscle mass and reducing muscle wasting during cancer, AIDS, and bedrest in adults.
The human studies analyzing the benefits of HMB supplements have mixed results. Therefore, future well-designed studies will assess the potency of HMB supplements as an anti-catabolic agent.