Article courtesy of Muscle and Fitness Forum
Beta-hydroxy-beta-methylbutyrate, or HMB, has been touted as a potential muscle-building supplement for two decades, but it continues to confuse lifters and health enthusiasts. While some people report great gains from HMB, others get nothing out of it.
Why this discrepancy? And will HMB work for you, or is it a waste of time and money?
Gym lore may help you get an idea about what HMB can do, but only science can give you the real story. Here is what the research has to say.
Scientists first began reporting on the protein-turnover effects of the branched-chain amino acid leucine back in 1984. That’s when SO Kong and DK Layman found that leucine fed to rats could increase the rate of protein synthesis and reduce the rate of proteolysis — muscle breakdown — when the animals were starved of dietary protein for an extended period of time.
Subsequent research found that the amount of leucine needed to slow proteolysis was greater than that needed to boost synthesis, which led to speculation that a metabolite of leucine, rather than the amino itself, was responsible for the protein-sparing action.
Scientists confirmed in the 1990s that one of those leucine byproducts, HMB, could indeed reduce the rate and extent of proteolysis in humans. One of the first studies to examine this phenomenon came from Iowa State University in 1996, where researchers subjected men to intense training either three days per week for three weeks or six days per week for seven weeks. Though the muscular and systemic stressors were more severe in the second study, subjects fed HMB in both studies showed a marked decrease in proteolysis over those given a placebo.
Of course, the end goal for bodybuilders is not to simply improve their protein turnover ratio but to actually build muscle. Fortunately, many of the studies around HMB stemming from the earlier research did examine the supplement’s effects on muscle growth. In fact, even that 1996 study from Iowa State found significant mass increases with HMB use when compared to a placebo.
An early review of related studies, published in 2000 by scientists from Australia, found fairly consistent positive results in terms of muscle growth among HMB users who were previously untrained. However, of the 10 “papers” reviewed at the time, only two were full journal articles, while the others were just abstracts of preliminary studies, calling into question their usefulness.
The next few years were fairly active in terms of HMB research, and scientists from the University of Illinois put together another review in 2008.
This time, there were dozens of studies available from which to draw conclusions, and the reviewers found:
- 5 studies that showed ergogenic effects when previously untrained subjects took HMB in conjunction with a weight training program. Lifters in these experiments gained both mass and strength when using HMB as compared to a placebo.
- Experienced trainees in 9 studies also benefited from HMB supplementation. The benefits for these groups included improvements in strength, mass, and VO2 max, an indicator of cardiovascular capacity. The combination of these three areas is especially important for athletes, who typically need superb strength AND endurance, and often body mass, too.
- 4 studies found that HMB could help elderly subjects gain mass and strength, or at least make improvements in the so-called “get-up-and-go” tests.
- 11 studies that suggest improved immunity and strength for subjects with disease states that typically cause severe muscle catabolism.
- A handful of other studies which showed muscle-growth improvement for subjects who did not fit neatly into the above categories.
On the other hand, the authors reported on some eight studies which did not support the idea that HMB can improve muscle growth and strength in human subjects. Part of the reason for the discrepancy can be attributed to training intensities, as HMB appears to work best only when severe muscle trauma is part of the mix: victims of disease, new trainees, lifters engaged in new or very intense workouts.
Virtually every study into HMB has reported no negative side effects for the subjects involved. In fact, a 2000 literature review found that, not only does HMB not seem to harm humans, it also tends to lower total cholesterol, low-density lipids (LDL), and systolic blood pressure. Results across nine studies showed those effects to represent improvements of 5-10% when compared to a placebo.
The Illinois researchers found similar trends during their 2008 review. In particular, they cite six studies that show improvements in blood lipid levels or blood pressure readings among subjects taking HMB, though the reviewers note that those effects seem to be most pronounced among those who had high cholesterol or blood pressure levels to begin with.
All told, the science behind HMB paints it as a supplement that can help you build muscle and strength, provided you are training really intensely, with few side effects.
If you’re not busting your butt in the gym, though, HMB probably won’t help you much and will more likely be just a waste of money.
And, of course, you need to be careful with any substance you put in your body. Talk to your doctor before taking HMB and let him know your plans. Together, you can decide if HMB will be safe and effective for you.