The A,B,Cs of HMB

By Lee A. Mancini, MD, CSCS, CSN

Introduction
The initials HMB stand for ß-hydroxy-ß-methylbutyrate which is a metabolite of the essential amino acid leucine. Currently an extremely popular supplement, sales of HMB in 1998 were between 50 and 60 million dollars.1 Essential amino acids are those that our bodies cannot make on their own, but rather ones that we need to consume from food sources. HMB is metabolized to hydroxymethylglutamyl-coenzyme A. This enzyme is the rate-limiting enzyme used when cholesterol synthesis is in demand. This happens when cell membranes need to be repaired during muscle damage and to enhance recovery.2 HBM is found in higher quantities in catfish, citrus fruit, and breast milk. It has been marketed as an ergogenic aid that preserves lean body mass during fat loss and as an anti-catabolic agent. An anti-catabolic agent is a substance that prevents muscle breakdown. This can be especially helpful when people are trying to lose weight and don’t want to lose hard earned muscle.

Proven Performance Effects
Men and women in their 70s took 3g/day of HMB for eight weeks. Both control and HMB supplementation groups resistance trained throughout the eight weeks. From this study the HMB group had statistically significant increases in lean body mass, decreases in fat mass, and increases in both upper and lower one repetition maximum strength over the control group.3 In other words, these 70 year olds who took HBM while lifting got stronger, dropped body fat, and gained more lean muscle mass than their counterparts who only completed the strength training. Supplementation with HMB at 1.5g/day and 3.0g/day significantly increased strength in conjunction with protein supplementation and resistance training when compared to protein supplementation and resistance training alone.4 HMB in cyclists has also been shown to increase the time to reach peak oxygen update and delay time to fatigue when compared to the control group.5 A Meta-analysis of supplementation with HMB compared nine studies that showed a statistically significant increase in lean body mass of 0.28% body mass per week and 1.40% single rep maximal strength gain per week vs. placebo groups.6

As for the recooperative abilities of HMB, there is evidence that it does decrease muscle breakdown. A study of exercise induced muscle damage after heavy resistance training showed that supplementation with 1.5g/day or 3.0g/day of HMB had significantly decreased protein breakdown and increased muscle recovery compared to the control group.7 Another study had subjects supplement 3g/day of HMB for six weeks while training for a 20K run.5 After the run, subjects from both the control and HMB groups had LDH and CPK levels drawn as they are indicators for muscle damage. The HMB group had significantly lower levels of LDH and CPK post-exercise. So in examining the evidence, HMB does preserve lean muscle mass when athletes or ordinary people are trying to lose bodyfat. It also does help people recovery from intense strength training sessions as well.

Adverse Effects
Studies have been done to see if there are any side effects to HMB supplementation. A six-week study with HMB supplementation showed no change in serum testosterone, cholesterol, triglyceride, urea, or glucose levels. There were no reported adverse effects from HMB use.1 Another safety study showed no change in renal function, LFTs, and lipid levels after using HBM for eight weeks.2 In fact, there have been no reported side effects in any studies examining the use of HMB.

Summary
HMB may help aid athletes in recovering from strenuous training sessions, may increase maximal strength, and may increase fat loss while maintaining muscle mass. It is not banned by the IOC, the NCAA, or any other sports governing body. Furthermore, studies examining short term use have found no side effects or adverse effects. The one drawback for HMB use may be its price; a one month supply of this supplement may cost 50 to 60 dollars.

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Note:  Lee A. Mancini graduated from Harvard as a two-sport athlete with honors in biology. Board certified in sports medicine and family practice, he works at the Family Health Center and UMass Sports Medicine Center in Worcester . He trains select clients as a certified strength and conditioning specialist and sports nutritionist. If you are interested in hiring him to design an individualized program, click here for our paid consultation services.

References

1. Crowe, M.J., O’Connor, D.M., & Lukins, J.E. (2003, June). The effects of ß-hydroxy-ß-methylbutryrate (HMB) and HMB/creatine supplementation on indices of health in highly trained athletes. International Journal of Sport Nutrition & Exercise Metabolism, 13(2), pp. 184-198.

2. Juhn, M.S. (2003). Popular sports supplements and ergogenic aids. Sports Medicine, 33(12), pp. 921-939.

3. Kreider, R.B. (1999, February). Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Medicine, 27(2), pp. 97-111.

4. Nissen, S., Sharp, R., & Ray, J.A. (1996). Effect of leucine metabolite ß-hydroxy-ß-methylbutyrate on muscle metabolism during resistance-exercise training. Journal of Applied Physiology, 81, pp. 2095-2104.

5. Knitter, A.E., Panton, L., Rathmacher, J.A., Petersen, A., & Sharp, R. (2000, October). Effects of ß-hydroxy-ß-methylbutyrate on muscle damage after a prolonged run. Journal of Applied Physiology, 89(4), pp. 1340-1344.

6. Nissen, S.L., & Sharp, R.L. (2003, February). Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis. Journal of Applied Physiology, 94(2), pp. 651-659.

7. Nissen, S.L., & Abumrad, N.N. (1997). Nutritional role of leucine metabolite ß-hydroxy-ß-methylbutylrate (HMB). Journal of Nutrition and Biochemistry, 8, pp. 300-311.