Hydroxymethyl Butyrate (HMB)
• Beta-Hydroxy Beta-Methylbutyric Acid
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.
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.
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 anti-anxiety drugs.
According to some but not all of the small double-blind trials performed thus far, HMB may improve response to weight training.
One small double-blind,
What Is the Scientific Evidence for Hydroxymethyl Butyrate?
In a controlled study, 41 male volunteers age 19 to 29 years old were given either 0 g, 1.5 g, or 3 g of HMB daily for 3 weeks. 12
In another controlled study reported in the same article, 32 male volunteers took either 3 g of HMB daily or placebo, and then lifted weights for 2 or 3 hours daily, 6 days a week for 7 weeks. The HMB group saw a significantly greater increase in its bench-press strength than the placebo group. However, there was no significant difference in body weight or fat mass by the end of the study.
Similarly, a double-blind, placebo-controlled trial of 39 men and 36 women found that over a period of 4 weeks, HMB supplementation improved response to weight training.
Two placebo-controlled studies in women found that 3 g of HMB had no effect on lean body mass and strength in sedentary women, but it did provide an additional benefit when combined with weight training.
However, other small studies have found marginal or no benefits with HMB for enhancing body composition or strength.
When the results of small studies contradict one another, it often means that the studied treatment produces minimal benefits at most, and this may be the case with HMB. Larger trials will be necessary to truly determine the extent of its effect.
HMB seems to be safe when taken at standard doses. 18
As with all supplements taken in very large doses, it is important to purchase a quality product, as an impurity present even in very small percentages could add up to a real problem.
2. Ostaszewski P, Kostiuk S, Balasinska B, et al. The effect of leucine metabolite 3-hydroxy-3-methylbutyrate (HMB) on muscle protein synthesis and protein breakdown in chick and rat muscle [abstract]. J Anim Sci. 1996;74(suppl 1):138.
11. Ostaszewski P, Kostiuk S, Balasinska B, et al. The effect of leucine metabolite 3-hydroxy-3-methylbutyrate (HMB) on muscle protein synthesis and protein breakdown in chick and rat muscle [abstract]. J Anim Sci. 1996;74(suppl 1):138.
21. Jowko E, Ostaszewski P, Jank M, et al. Creatine and beta-hydroxy-beta-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program. Nutrition. 2001;17:558-566.
22. Slater G, Jenkins D, Logan P, et al. Beta-hydroxy-beta-methylbutyrate (HMB) supplementation does not affect changes in strength or body composition during resistance training in trained men. Int J Sport Nutr Exerc Metab. 2001;11:384-396.
23. Ransone J, Neighbors K, Lefavi R, et al. The Effect of beta-Hydroxy beta-Methylbutyrate on Muscular Strength and Body Composition in Collegiate Football Players. J Strength Cond Res. 2003;17:34-39.
25. Hoffman JR, Cooper J, Wendell M, et al. Effects of beta-Hydroxy beta-Methylbutyrate on power performance and indices of muscle damage and stress during high-intensity training. J Strength Cond Res. 2004;18:747-52.
26. Lamboley CR, Royer D, Dionne IJ. Effects of beta-hydroxy-beta-methylbutyrate on aerobic-performance components and body composition in college students. Int J Sport Nutr Exerc Metab. 2007;17:56-69.
Last reviewed April 2009 by EBSCO CAM Review Board
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