Technically 'beta-hydroxy beta-methylbutyric acid,' HMB is a chemical that occurs naturally in the body when the amino acid leucine breaks down.

Leucine is found in particularly high concentrations in muscles. During athletic training, damage to the muscles leads to the breakdown of leucine as well as increased HMB levels. Evidence suggests that taking HMB supplements might signal the body to slow down the destruction of muscle tissue. However, while promising, the research record at present is contradictory and marked by an absence of large studies.

HMB is found in foods of both plant and animal origin, and HMB is also normally produced in the body. (Depending on the nutritional program, from .3 grams to 1 gram of HMB is produced in the body per day.) Its precursors are the amino acid leucine and the keto acid KIC. Certain plants such as alfalfa and plant products such as corn silage appear to have relatively large concentrations of HMB. Grapefruit and catfish also contain relatively high concentrations of this nutrient. However, similar to various vitamins and other micronutrients, it is extremely difficult and impractical to consume enough of these foods on a regular basis to provide the full benefits of HMB. It is probably much more practical to use a dietary supplement containing pure HMB.

HMB is not an essential nutrient, so there is no established requirement. HMB is found in small amounts in citrus fruit and catfish. To get a therapeutic dosage, however, you need to take a supplement in powder or pill form.

Therapeutic Uses
According to most but not all of the small double-blind trials performed thus far, HMB may improve response to weight training. HMB might help prevent muscle damage during prolonged exercise. A typical therapeutic dosage of HMB is 3 g daily.

Be careful not to confuse HMB with gamma hydroxybutyrate (GHB), a similar supplement. GHB can cause severe sedation, especially when combined with other sedating substances, such as alcohol or antianxiety drugs.

Since all of the positive effects of HMB use have been linked to intense exercise, what is the rationale for using HMB on non-training days?
It's probably important to continue taking HMB even on your off days and here's why. Not only does HMB play a role in protecting your muscles from excessive damage, it may also aid in the growth and repair of muscle tissue during your days away from the gym. If you avoid taking HMB on these days, you may be missing the opportunity to boost your recuperative abilities.

However, it may make sense to take less HMB on non-training days. And here's something else to consider about taking HMB: some anecdotal and research-based information seems to indicate that it may be beneficial to take more HMB than the recommendation of three grams per day. Some athletes have experienced improved results from as much as five grams per day. Experts have speculated that the improved benefits of higher dosages may be due to the bodyweight of these weight-training athletes, as many of them weigh much more than 200 pounds. So if you're well over 200 pounds, a sample HMB dosing schedule may be trying five or six grams on training days and two to three grams on off days.

Although the total amount of HMB may be reduced on non-training days, it's important to increase the frequency of HMB supplementation to maintain a consistent blood level and thereby potentially increase its effectiveness. For example, you might try consuming a half-serving of HMB five or six times a day rather than a full serving three times a day.

I was wondering if the recommended dosage of supplements like creatine and HMB should be adjusted according to bodyweight or gender?
Although studies have not been done to answer this particular question, logic dictates that if a 200-lb guy gets good results using 3 grams of HMB a day, a 135-lb woman should get good results by using 2 grams a day.

It also seems to make sense that if a 200-lb athlete experiences positive results using a maintenance dose of creatine (6-10 grams), then a woman who weighs 135 lbs might need only 4-6 grams of creatine a day.

By the same token, atheletes who weigh over 200 lbs might benefit from taking more of these supplements to get optimal results.

Can I get the same effects of HMB by taking the amino acid leucine?
Probably not. Researchers currently believe 5% of dietary leucine is converted to HMB in the body. To make 3 grams of HMB in your body, you would have to take at least 60 grams of leucine per day, which is not practical and could cause severe stomachaches!

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