[Advertised Claims] [Description] [Commercial Availability and General Use] [Ergogenic Effects] [Risks and Disadvantages] [Recommendations]
| Advertised
Claims |
HMB is short for ß-hydroxy-ß-methylbutyrate. It is a natural compound produced in the body and small amounts of it can be found in certain foods such as catfish and alfalfa [1].
In the body, HMB is derived from the branched-chain amino acid, leucine. A portion of the leucine within the skeletal muscles is metabolized into the intermediary product, µ -ketoisocaproate (KIC) via transamination. Dioxygenase converts KIC into HMB in the cytosolic compartment. Approximately 5% of the leucine in the body each day is converted to HMB producing about .2 to .4 g of HMB a day in a 70-kg individual [2].
Animal studies show that HMB supplementation may increase survival rates and/or increase lean body mass in domestic animals subjected to various kinds of stress. The general theory is that HMB reduces or prevents protein breakdown in these animals. Thus HMB is now available as a dietary supplement for humans, particularly bodybuilders and other athletes who are trying to increase lean body mass and muscle strength.
| Commercial
Availability and General Use HMB is sold in most major, health food stores as calcium-HMB. Cost of the supplement is approximately $30 for a 10-day supply. All genuine forms of the supplement must bear the patent number, U.S. Patent 5,348,979 on the product label. HMB is classified as a food supplement and not a drug. HMB appears to have a short half-life (2-3 hrs.) in the blood [2]. Therefore, its manufacturers recommend that HMB be ingested in several divided doses throughout the day (for example, one gram of HMB three times daily). Current research is investigating the possibility that creatine supplementation may enhance the benefits of HMB supplementation. |
Prevents muscle catabolism, speeds muscle repair, and increases lean body mass
Two of HMB’s precursors, leucine and KIC, were found to prevent or slow proteolysis in incubated muscle tissue (in vitro) [3], and KIC itself was marketed as a bodybuilding supplement. But it was later hypothesized that the downstream product, HMB, could be more effective in preventing or reducing muscle loss in humans and animals.
However, the actual mechanisms of HMB metabolism are not known. One hypothesis suggests that HMB directly inhibits the catabolism of muscle proteins during stressful events such as exercise. Another possibility is that HMB is a structural component covalently linked to tissues or cell membranes and is destroyed when under stress. Thus, supplementation with HMB may both prevent muscle breakdown as well as accelerate tissue repair after exercise [2].
Much research on HMB has been done on domestic animals such as horses or cows. The objective was to maximize weight gain in the animals (and prevent weight loss caused by stress) and to strengthen their resistance against disease. Indeed, studies showed that the mortality rates of animals decreased upon HMB supplementation. Furthermore, lean body mass increased in many of the animals, and the immune systems of many of these animals were improved as well. For example, studies reported an increased survival rate in newly hatched chicks and feedlot steers that were fed HMB [4,5]. Also, lactating sows that were fed HMB were able to produce larger amounts of milk, and the baby pigs increased in size and had a higher survival rate [6].
A study conducted by Nissen et al. reported an increase in upper and lower body strength in human subjects (untrained male volunteers aged 19-29) that took HMB. The increases in strength were proportional to the amount of HMB supplemented into the diet. Also, the study reported an increase in lean body mass that was proportional to the amount of HMB ingested [2].
Another significant finding in this study was a marked decrease in the amount of 3-methyl histidine in urine samples as well as decreased plasma concentrations of essential amino acids, creatine kinase, and lactate dehydrogenase after three weeks of supplementation. This indicated a reduction in the muscle breakdown that normally occurs during intense exercise.
For the most part, this study was well controlled However, the study was conducted over a period of only a few weeks. Since the subjects were untrained, it seems likely that most of the strength increases would be a result of neural adaptation and not necessarily an increase in muscle mass. Furthermore, the training protocol (2 warm-up sets followed by 2 sets of 3-5 reps) used in the study favors increases in strength but generally is not the one used to elicit muscle growth. A higher number of repetitions (6-12) is more likely to favor increases in muscle mass.
Other Research Investigating the Effects of HMB Supplementation on Human Subjects
Nissen et al. reported significant gains in fat-free mass and strength in 37 untrained female subjects who consumed 3.0 g HMB per day for 4 weeks. All subjects underwent a resistance training program during the study. In an earlier study conducted by Nissen and colleagues, 36 women received the same amount of HMB for 4 weeks but did not undergo a resistance-training program. No significant changes in fat-free mass or strength were reported in these subjects [7].
Kreider et al. recruited 40 resistance-trained athletes for their study. The subjects consumed a carbohydrate/protein drink along with 0, 3, or 6 g HMB per day for 28 days. The subjects were tested before and after the treatment period for body composition and strength (leg press and bench press). No significant changes were reported in body composition or strength among the three groups [8].
Vokovich et al. supplemented the diets of 15 elderly men and 16 elderly women (aged approximately 70 years) with 3 g HMB each day for 8 weeks. A significant gain (1.5%) in fat-free mass and a significant reduction (-4.1%) in fat mass was reported in the HMB-supplemented subjects. Furthermore, these subjects improved in lower body strength [9].
.
Decreases body fat and blood cholesterol levels
HMB supplementation has been reported to reduce fat mass in the body. This may be the result of increased lean body mass (lean body mass oxidizes fatty acids) although some research is investigating possible mechanisms in which HMB directly plays a role in the oxidation of fatty acids [10]. Also, feedlot steers that were fed HMB reportedly had reduced plasma cholesterol levels [5]. HMB may be converted to cholesterol in the muscles and thus may reduce plasma cholesterol levels by inhibiting the synthesis of cholesterol in the liver.
HMB and Creatine Supplementation
- Kreider et al. investigated the potential benefit of combining HMB and creatine supplementation [11]. 52 college football players participated in Kreider's study. All of the subjects were undergoing a resistance-training program and were divided into four groups in which subjects consumed one of the following for 28 days:
- 1). Placebo (carbohydrate + electrolyte solution)
- 2). Placebo + HMB (3g/d)
- 3). Placebo + creatine monohydrate (15.5 g/d)
- 4). Placebo + HMB (3g/d) + creatine monohydrate (15.5 g/d)
The subjects were measured before and after the supplementation period for body composition, maximal bench press, repetition tests for squats and power cleans, and performance on 12 sets of 6-s sprints (with 30 s recovery periods between sets) on cycle ergometers [11].
Significant gains in fat-free mass were reported in the group receiving the placebo + creatine and the group receiving placebo + creatine + HMB. However, no significant changes were reported in the group receiving the placebo + HMB. Furthermore, the gains in fat-free mass were not significantly different between the groups receiving creatine indicating that HMB did not contibute to these gains. No significant changes were reported in lifting or sprinting performance in any of the groups [11].
Risks and
Disadvantages
|
| Recommendations HMB is a relatively new supplement on the market advertised to increase muscle mass and strength when used in conjunction with a regular weight training program and an adequate protein diet. It is one of the most expensive nutrition supplements today, and so far it has received mixed reviews from users since it was introduced to the market in 1996. Many of the testimonials that endorse HMB contend that its results are not as immediately noticeable as the effects from creatine monohydrate but that in the long run, HMB produces long lasting results comparable to creatine. There is some scientific evidence to support the usefulness of HMB in both humans and animals. However, little is known about how HMB really works so methods of intake can only be vaguely recommended. Nevertheless, manufacturers of the supplement insist that it is safe to use and so far, no adverse side effects from HMB use have been shown. Of course, HMB has only been on the market for a few years, and more long-term studies must be conducted to examine any possible side effects resulting from chronic usage. Furthermore, pregnant and lactating women are not advised to use HMB because its nature is rather obscure. So the bottom line for HMB use is that the supplement may have good potential as an ergogenic aid for weightlifters and bodybuilders. However, the degree of its effectiveness and the methods of intake are still under investigation. |
Article by Richard Chiang 4/01/98
Updated 12/21/99
2. 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. J Appl Physiol. 1996;81:2095-2104.
3. Hong, S.O.C. Effects of leucine on in vitro protein synthesis and degradation in rat skeletal muscles. J Nutr.1984;114:1204-1212.
4. Nissen S, Fuller JC Jr, Sell J, Ferket PR, Rives DV. The effect of beta-hydroxy-beta-methylbutyrate on growth, mortality, and carcass qualities of broiler chickens. Poultry Sci. 1994;73:137-155.
5. Van Koevering MT, Dolezal HG, Gill DR, Owens FN, Strasia CA, Buchanan DS, Lake R, Nissen S. Effects of ß-hydroxy-ß-methyl butyrate on performance and carcass quality of feedlot steers. J Anim Sci. 1994;72: 1927-1935.
6. Nissen S, Faidley TD, Zimmerman DR, Izard R, Fisher CT. Colostral milk fat percentage and pig performance are enhanced by feeding the leucine metabolite beta-hydroxy-beta-methyl butyrate to sows. J Anim Sci. 1994;72: 2332-2337.
7. Nissen S, Panton L, Fuller J, Rice D, Ray M, Sharp R. Effect of feeding ß-hydroxy-ß-methylbutyrate (HMB) on body composition and strength of women. FASEB J. 1997;11:A150.
8. Kreider RB. Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Med. 1999;27:97-110.
9. Vukovich MD, Stubbs NB, Bohlken RM, Desch MF, Fuller JC, Rathmacher JA. The effect of dietary ß-hydroxy-ß-methyl butyrate (HMB) on strength gains and body composition changes in older adults FASEB J. 1997;11:A376.
10. Abumrad N. et al. Beta-hydroxy-beta-methylbutyrate increases fatty acid oxidation by muscle cells. FASEB J. 1997;11:A381.
- 11. HMB Website, Global Reach Internet Productions, Ames IA. http://www.global-reach. com/MTI
- Accessed March 28, 1998.
