What Is It?
Calcium beta-hydroxy-beta-methylbutyrate (Calcium HMB, or HMB for short) is a water soluble substance which is produced from the metabolism of the amino acid leucine. Leucine is one of three amino acids known as the Branched Chain Amino Acids (BCAAs), the other two are valine and isoleucine. BCAAs are commonly used for preventing muscle catabolism, enhancing protein synthesis, and improving exercise tolerance and performance. Of all the amino acids including the BCAAs, leucine has been found to have the greatest effect on protein synthesis.
The production of HMB begins when leucine undergoes a process known as transamination in muscle cells catalyzed by the enzyme branched chain aminotransferase (BCAT) which yields alpha-ketoisocaproate (KIC). Approximately 95% of KIC is then oxidized to isovaleryl-COA which then undergoes further metabolism. The remaining 5% of KIC undergoes oxidization catalyzed by the enzyme KIC-dioxygenase to produce HMB.
HMB was introduced to the national market in 1995 and gained enormous popularity among fitness enthusiasts, bodybuilders, and athletes however it has since faded into obscurity due to a widespread general lack of knowledge and understanding of this incredible substance. HMB stands among staples such as whey protein, glutamine, and creatine due to it’s several positive effects on protein synthesis and nitrogen balance, the immune system, cholesterol, increasing exercise performance, and metabolism of intramuscular fat (triglycerides). These effects are well established and clinically researched as HMB to this day reigns as one of the most well researched sports nutrition supplements.
It is estimated that HMB production in man is equal to 250mg to 1000mg per day depending on leucine intake. It is also found within our daily food supply. Certain foods including grapefruit, some lean meat and fish, and mother’s milk contain measurable amounts.
What Does It Do?
- Increases protein synthesis and improves nitrogen balance
- Helps prevent muscle catabolism
- Enhances the immune system
- Decreases total & LDL cholesterol, and raises HDL (good)
- Increases lactic acid threshold and VO2 Max
- Improves the metabolism of intramuscular fat
How Does It Work?
HMB is classified as an anti-proteolytic. Meaning it retards proteolysis which is the breakdown of proteins by cellular enzymes known as proteases. Administration of HMB has been shown to reduce markers of muscular damage including lactate dehydrogenase, creatine kinase, and 3-methylhistidine. Studies indicate that HMB stimulates protein synthesis through multiple mechanisms including the mTOR pathway. The mammalian target of rapamycin (mTOR) pathway plays a central role in the regulation of cell proliferation and protein synthesis. Leucine is also known to share this effect. Higher doses of HMB may also increase the production of somatomedins (IGF-1), one of the body’s most powerful muscle building compounds.
The majority of HMB is metabolized to beta-hydroxy-beta-methylglutaryl CoA (HMG-CoA) which can then be used for cholesterol synthesis through the enzyme HMG-CoA reductase. HMB-CoA reductase is rate-limiting when the demand for cholesterol in the body is high such as during periods of rapid cell growth or membrane repair. Cholesterol makes up approximately 13% of the cellular membrane. It plays an integral role in controlling the fluidity of the membrane. Damage to the cellular membrane through activities such as weight training or high intensity exercise effects the body’s demand for cholesterol. Cholesterol is also absolutely necessary for production of hormones, in particular testosterone. The ability to produce enough amounts of cholesterol under stress is extremely important for every athlete.
Athletes engaged in endurance and high intensity activities can benefit from HMB through its beneficial effect on the metabolism of intramuscular fat. HMB has also been shown to increase maximal oxygen consumption (VO2 Max), reduce metabolic acidosis and increase lactic acid threshold. Horses supplemented with HMB showed decreased muscle damage and increased aerobic performance during actual race conditions. Athletes using HMB become leaner, harder, stronger, faster and recover more efficiently than their non HMB supplemented peers.
Finally, HMB has also been found to boost the immune system. Studies in vitro and on animals has concluded that HMB increases the function and number of white blood cells. Building and maintaining a strong immune system is a key factor in athletic success.
How Safe Is it?
To this day, no known negative effects have been found from the supplementation of HMB. It is produced naturally within our own bodies and can be found within our food supply. You make it, your mom makes it, grandma makes it and your kids make it. HMB also has no contraindications.
How Should I Take It?
The general recommended dose of HMB is 3 grams. However research has shown that 38mg/kg body weight per day is optimal. HMB is a water soluble substance and therefore should be taken regularly throughout the day in divided equal doses for maximum benefit. It can be taken on an empty stomach, mixed with a juice or even better, with a protein shake. Taken before and after exercise ensures ample amounts of HMB available to the system to increase performance and decrease recovery time.
HMB taken with other supplements such as creatine and essential fatty acids such as those found in flax seed oil, hemp oil, and marine based oils will also amplify it’s positive effects. Research has shown that HMB combined with creatine produces greater results than either HMB or creatine alone. HMB also works just as well for women and women supplementing with HMB can even increase the HMB content of their breast milk, benefiting their feeding children.
HMB Studies
