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HBM:  A Dietary Supplement for Building Muscle?

Nic Vera





Three major companies (Twinlab, MetRx, and EAS) currently market the nutritional supplement HMB, or beta-hydroxy beta-methylbutyrate ( HMB has been highly acclaimed since itís recent market debut by EAS ( Many critics have compared it to the wonder-product Creatine Monohydrate. Such a comparison undoubtedly harbors both positive and negative aspects. But nevertheless, HMB products continue to thrive in nutritional stores worldwide.

I. What is HMB?

"HMB (hydroxy-methylbutraye) is a metabolite of the amino acid Leucine and is produced naturally by the human body. HMB is produced from a metabolite of leucine, called ketoisocaproate (KIC), by the enzyme KIC-dioxygenase. And, at least in the pig, HMB is produced exclusively from leucine"(Nissen p.2095).

II. How does HMB work?

Steven Nissen and his colleagues have performed the only study to date of HMB on humans. The researchers agree that the mechanism by which HMB impacts muscle proteolysis and function is not currently known. Nevertheless there are a number of postulations. "The high substrate concentration required by the dioxygenase enzyme compared with the liver concentration of KIC suggests that HMB production in the body may be a first-order reaction controlled by enzyme and KIC concentrations. It has been calculated that, under normal conditions, about 5% of leucine oxidation proceeds via this pathway. Therefore, if humans are assumed to have enzyme actions similar to those seen in pigs, a 70-kg human would produce from .2 to .4 g HMB/day depending on the level of dietary leucine. At leucine intakes of 20-50 g/day (which are used therapeutically), the concentrations of leucine and KIC in the liver increase and could result in HMB production reaching gram quantities per day"(Nissen p.2095). Some studies involving HMB supplementation to the diet of steers and pigs have been shown to improve caracass quality. Based on these findings, it has been hypothesized that supplementing the diet with HMB may inhibit protein degradation during periods of increased proteolysis such as resistance training.

III. What are the Claims?

The three companies that currently market the product recommend 1.5-3.0 grams of HMB/day as a dietary supplement. Although the science behind the productís effectiveness is rather unclear, all three companies show few distinctions between dosages and manufacturing. Most people who have noticed the product often see HMB advertised as a protein breakdown suppressor. Researchers claim that such an advantage actually enhances the gains in muscle strength and lean mass associated with resistance training. Companies who promote the product claim that humans neither produce enough HMB in their bodies, nor do they eat such HMB-containing foods (e.g. catfish and grapefruit) regularly enough to provide the full benefits of HMB. Researchers claim that when we input extra amounts of HMB into our bodies the metabolite acts as a performance enhancer for such activities as weight lifting and sprinting. In effect, companies claim that HMB boosts strength levels, enhances gains in muscle size and strength, and prevents post-workout muscle tissue breakdown. The marketing companies do not make exactly clear how the product works, but they have formulated a few widely accepted ideas which are seen on the advertisement postings in many nutritional stores. Many of them believe that excess amounts of HMB in the body cause an interference with the bodyís natural process of protein breakdown (particularly after a workout). In doing so, HMB allows athletes to retain more protein in their system, resulting in increased energy levels and faster recovery. Of course the companies claim that this product is only beneficial to those who workout in addition to HMB supplementation. Internet advertisements claim that there are countless experiments involving placebos and HMB supplements, which have resulted in substantial performance increases in the many groups of athletes who have taken HMB along with their training regimen.

IV. First Impressions

In my search for information about HMB, I found that most of the claims and information were fairly similar. Since so few companies actually market the product such a common thread is expected. I did find it interesting however that none of the companies recognized any side effects whatsoever throughout all of the experiments and research of the product. This concern has become all too familiar in the recent explosion of nutritional products. Perhaps there is more to be discovered about HMB in cases of long-term usage.

V. What is the Research Evidence?

As I began searching for information on the 'countless studies' involving HMB and its connection to athletic performance, I noticed that it was rather difficult to pinpoint any studies involving humans. And even the studies on animals were limited. This is more than likely due to the fact that HMB is a relatively new product on the market. The one primary research report on humans that I found was a very popular one. I noticed that many of the review papers used it is a reference tool. The study was conducted by Steven Nissen, and a number of his colleagues in November 1996.

A. Nissen Study

  1. What was the question? Nissen and his colleagues wanted to know what the effects were of HMB on muscle metabolism during resistance-exercise training.
  2. What methods were used? Nissen used two studies to determine the effects that HMB had on muscular metabolism. In his first study, Nissen took a randomized sample of 41 individuals and divided them randomly into three different levels of HMB intake (0,1.5, and 3 g HMB/day) and two protein levels (117 g/day and 175 g/day). In all of the groups the subjects lifted weights for 1.5 hours and three days a week for three weeks.

  3. In the second study Nissen took another random sample of 28 individuals and divided them randomly into two levels of HMB supplementation (0 and 3 g HMB/day). In both groups, the subjects lifted weights for 2-3 hours and 6 days per week for 7 weeks.

  4. What were the results? In the first study, HMB greatly decreased the muscle proteolysis as well as the levels of plasma creatine phosphokinase. Additionally, the amount of weights lifted increased with HMB supplementation when compared with the unsupplemented group. During each week of the second study, fat-free mass was significantly increased in HMB supplemented subjects compared with the unsupplemented group. Nissen and colleagues thus concluded that supplementation with either 1.5 or 3 g HMB/day can partly prevent exercise-induced proteolysis and/or muscle damage. Additionally, the dietary supplementation of HMB can result in larger gains in muscle-mass associated with resistance training.

B. Papet Study (Papet, et al. June 1997)

  1. What was the question? I. Papet and his colleagues designed an experiment to study the effect of a high dose of HMB on the protein metabolism in growing lambs.
  2. What methods were used? Six two-month old lambs were divided into two groups. The first group was the experimental group and involved the supplementation of a high dosage of HMB and the second group was a control for the experiment using only a calcium compound. In order to effectively study the protein metabolism, Papet used three methods consecutively 2.5 months after beginning the treatment. He used whole body phenylalanine fluxes, postprandial plasma free amino acid time course, and fractional rates of protein synthesis in skeletal muscles.
  3. What were the results? From the second test, Papet and colleagues reported that feeding a high dose of HMB led to a significant increase in some plasma free amino acids compared with the controls. The first method, which tested the phenylalanine flux, proved unchanged in both groups. Similarly in the last test of fractional rates of protein synthesis, both groups showed no change upon examination of skeletal muscles. Collectively, the results manifested that a high dosage of HMB was able to modify plasma free amino acid patterns without any effect on whole-body protein turnover and skeletal muscle protein synthesis. Such an observation suggests that there are no significant protein intake and HMB interactions. This further supports the idea that the effects of HMB on metabolism are additional to and independent of protein intakes. Therefore, even though HMB is a metabolite of leucine, simply consuming more protein containing a large amount of the amino acid leucine would not be comparable to dietary HMB supplementation.

C. Van Koevering Study (Van Koevering, et al. August 1994)

  1. What was the question? Van Koevering and his colleagues designed an experiment in order to determine the effects of HMB on the performance and carcass quality of feedlot steers.
  2. What were the methods used? Van Koevering and his colleagues took a random sample of 256 crossbred steers and divided them into two groups. One group was given .03% of diet dry matter and the other was given 0%. The effects on the performance, carcass characteristics, and tissue composition were measured. Groups of 32 steers per diet were killed after 105, 119, 133, and 147 days on the feed. The HMB was fed to each group only during the final 82 days they were fed.
  3. What were the results? The researchers noticed an interaction between HMB and the time on the feed, in that feeding HMB increased daily gain of steers slaughtered at 105 days, but decreased the daily gain of steers slaughtered at 147 days. Additionally the steers fed HMB had higher carcass quality grades, as well as a higher ratio between fat muscle and skin fat. The HMB steers also had higher blood plasma concentrations of HMB and lower blood plasma concentrations of cholesterol.

VI. Primary Research Wrap-Up


Due to the fact that a limited number of HMB studies have been performed on humans, we must also consider the results of the tests on animals. Perhaps there is a connection between the noted improvements in the two animal tests and those of humans. This data alone, however, is insufficient. Since HMB is a relatively new product, one must take into consideration the possible side effects or other negative aspects of upsetting a natural balance within the body. There were a few review papers that I found expressing both skepticism and praise of HMB as a dietary supplement.

VII. Review Paper Reactions to HMB Studies/Claims

  1. Researchers, Clarkson and Rawson, published an article concerning a number of the nutritional supplements currently on the market and their effect on human muscle mass. Not surprisingly, they spent a good portion of the article on creatine, which was introduced several years ago as a body-building supplement. As a result of its tenure, creatine has much more information available regarding its functions and effectiveness. Additionally there are more studies on creatine than HMB. Nevertheless, the researchers covered most of the supplements including HMB. Although brief, Clarkson and Rawson commented on the performance of HMB as a nutritional supplement. They recognized Nissen's, "preliminary work on HMB and its support of the claim that HMB has an anticatabolic effect on the muscles"(Clarkson p.320). They also emphasized the fact, however, that only one human study is currently available, and therefore the existing data is inconclusive.
  2. Another review of HMB was done by Kreider. His study of the product was similar in fashion to that of Clarkson and Rawson, in that he took a number of dietary supplements and examined whether or not they are effective in the promotion of muscle growth with resistance exercise. He also recognized Nissen's study as well as those on the animals in his commentary. Kreider focused on the dietary supplementation of HMB and its marketers' claim that it promotes gains in fat-free mass during bouts of exercise. He uses Nissen's study to argue that HMB has been shown to positively affect athletic performance. But here again, there is little time spent on the subject of HMB and it's effectiveness. It seems appropriate that comments on the research evidence are sparse, since there is only one human study to date. As a further commentary, a researcher Mero developed an article, which focused on Leucine supplementation and intensive training. However, as yet another roadblock in the way of finding review papers focused on the study of HMB, Mero remarked that there have been very few studies done with Leucine alone. He argues that, "most studies involve leucine supplemented as part of a mixture of another compound"(Mero p.351). The conclusions are therefore not likely to reflect the performance of HMB alone. And again, Mero (like the other authors) referred to Nissen's study as being the only controlled manifestation of HMB's performance on resistance-trained human beings.
  3. VIII. Are There Any Confounding Variables in the HMB Study on Humans?

    Since there is only one concrete study of the effects of HMB on the athletic performance of human beings, confounding variables are of great importance. If a lurking variable were to skew the results of Nissen's study then the base of support for the companies claims would be unsubstantiated. Therefore I proceeded with caution when formulating a final opinion on the effectiveness of HMB. In reading through Kreider's review paper on Nissen's study, I found a possible lurking variable. Kreider realized that in the one study that reported significant gains in fat-free mass in resistance-trained athletes, "HMB was added to a popular carbohydrate/protein vitamin/mineral fortified meal replacement supplement"(Kreider p.107). Therefore it is unclear whether HMB supplementation and/or some other combination of nutrients was responsible for the gains in fat-free mass observed. This is undoubtedly an important consideration in reviewing the study, which has the potential to be the basis for a concerned consumer's opinion.

    IX. Final Impression

    After reviewing the sparse and conflicting information regarding the effectiveness, I came to the conclusion that there is simply not enough concrete evidence to support the claim that HMB promotes the growth of lean muscle mass and reduces proteolysis. This is not to say that the product is unsafe, especially since, to my knowledge, there have been no contradicting studies or documented side effects from the product. I did, however, discover a few of the underhanded marketing techniques used by the companies. They claimed that there were countless research studies, which proved HMB's validity as an effective nutritional supplement. This was not nearly the case. The simple fact that a resourceful university library produced only one study involving HMB on humans, is evidence enough to argue that the promoters are over-generalizing the facts behind the study of the product. The companies backing HMB have made a number of claims that their product is beneficial to resistance-trained athletes. So far there have been no concrete indications suggesting otherwise.

    X. References

    1. Nissen S; Sharp R; Ray M; Rathmacher JA; Rice D; Fuller JC Jr; Connelly AS; Abumrad N, "Effect of Leucine Metabolite Beta-Hydroxy-Beta-Methylbutyrate on Muscle Metabolism During Resistance-Exercise Training"  Journal of Applied Physiology (November 1996): 2095-2104
    2. Clarkson PM; Rawson ES, "Nutritional Supplements to Increase Muscle Mass" Clinical Review of Food, Science and Nutrition (July 1999): 317-328
    3.  Kreider RB, "Dietary Supplements and the Promotion of Muscle Growth with Resistance Exercise" Sports Medicine (February 1999): 97-110
    4. Mero A, "Leucine Supplementation and Intensive Training" Sports Medicine (June 1999): 347-358
    5. Papet I; Ostaszewski P; Glomot F; Obled C; Faure M; Bayle G; Nissen S; Arnal M; Grizard J, "The Effect of a High Dose of HMB on Protein Metabolism in Growing Lambs"
    6. British Journal of Nutrition (June 1997): 885-896
    7. Van Koevering MT; Dolezal HG; Gill DR; Owens FN; Strasia CA; Buchanan DS; Lake R; Nissen S, "Effects of Beta-Hydroxy-Beta-Methylbutyrate on Performance and Carcass Quality of Feedlot Steers" Journal of Animal Sciences (August 1994): 1927-1935



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