Base Knowledge: HMB

This supplement is shown to prevent muscle wasting in old folks--but can it help athletes?

Today, let’s discuss hydroxymethylbutyrate—or HMB to its friends. Admittedly, this is a neck-snapping pivot from last week’s aromatic subject matter, but stick around. I spoke with a trio of scientific experts who have published hundreds of papers on sports supplementation, so this week’s newsletter contains legit answers and actual journalism. More or less.

What is HMB?

Protein is made of amino acids. Loosely defined as “the body’s building blocks,” amino acids play all sorts of roles. We use 20 amino acids, but we’re not capable of producing nine of them, so we need them in our diet. These are the “essential amino acids.”

Three of these essential amino acids have an extra branch on their chemical structure, earning them the title “branched chain amino acids.” BCAAs play a special role in muscle repair and recovery—although I think they’re overrated as a supplement, considering you can get all the BCAAs you need from whole protein sources.

The rock star of the BCAAs is leucine since it’s especially good at stimulating muscle protein synthesis (building and repairing muscle). It can also ward off the kind of muscle breakdown that, for example, happens when you age.

HMB is a metabolite of leucine. Metabolites are substances made when the body breaks down food, drugs, chemicals, and (sometimes) its own tissue. They play different roles associated with metabolism. HMB is a big part why leucine works.

In case you’re wondering why you shouldn’t just use leucine, to get the 3-gram dose of HMB shown to be effective means consuming 60 grams of leucine—or 600 grams of high-quality protein—or 100 eggs. Good luck with that.

Does HMB work?

When it comes to helping older people ward off sarcopenia and maintain or build muscle, the research is compelling. A 2022 meta-study looking at a combined 896 elderly subjects found the benefits of using HMB to be “statistically significant.”

But if you don’t happen to be old and you’re wondering if it’ll help with your workout, things get a little tricky. If you’re under 50, you eat right, and you don’t destroy yourself on a regular basis, probably not.

“There's a lot more evidence to suggest that HMB could help to stave off age-related decline in metabolic health and muscle mass,” Dr. Chad Kerksick, FISSN, CISSN, Associate Professor of Exercise Science at Lindenwood University told me. “But it's pretty well-accepted that, for healthy populations who are resistance training while getting enough calories and enough protein in their diet, adding HMB is very likely not going to add much to their regimen.”

HMB doesn’t prevent the “tear it down and build it back stronger” kind of acute breakdown that happens when you push muscle hard during a workout. Instead, it prevents muscles from wasting away due to more insipid stressors—aging, for example. In these situations, it’s thought to have anti-catabolic (anti-breakdown) properties.

But there are other stressors beside aging, such as eating at a calorie deficit—where your body might start cannibalizing muscle to use as fuel. Or destroying yourself on regular 126-mile bike rides or 16-mile runs—where you’re probably overtraining, under-eating, and not allowing enough time for your muscles to recover. In these circumstances, HMB might potentially help.

“When we're not properly fueled, like during very heavy periods of training or for weight class athletes going through purposeful periods of energy deprivation, these are very catabolic environments,” said Kerksick. “In these situations, it makes sense why adding in HMB might help to avoid the loss of muscle tissue—but that's speculation on my part.”

Dr. Ralf Jäger, MBA, FISSN, co-founder of consulting firm Increnovo, is a little more positive about HMB, but ultimately agrees it’s not for everyone. “If you're a person that works out a lot and doesn't get enough recovery, then yes, absolutely,” he said. “If you're an older athlete, yes, absolutely. If you're a 20-year-old kid that just wants to put on some pounds, I would just stick with creatine and protein.”

An HMB and creatine cocktail.

A few of my cyclist readers inquired about the combination of HMB and creatine. (Shout out to Todd and Patrick! Endurance nerds in the house!)

It sounds obviously beneficial—theoretically speaking. “With creatine, you have more available energy, so you should be able to train harder,” proposed Jäger. “If you add HMB to that, because you are working hard, it helps you to recover faster so you have less muscle damage. So as a consequence, if you combine the two, creatine allows you to push harder and HMB allows you to keep the muscle mass and recover faster.”

“They should be synergistic. ‘Should’ is the key word,” said Douglas Kalman, PhD, RD, FISSN, co-founder of Substantiation Sciences. “There's only been a handful of studies that looked at HMB plus creatine in various athletic settings and unfortunately, the majority of them do not show any synergistic effects beyond either alone.

“But that doesn't mean that these two ingredients may not have synergy. That may mean the types of studies and the study designs may have not asked the right questions to elicit whether there is some type of additive effect.”

One 2020 placebo-controlled, double-blind study did show an effect—heads up, endurance athletes—on elite male rowers training to exhaustion. After 10-weeks, the HMB and creatine combo was shown to “have a synergistic effect on aerobic power during an incremental test but had no influence muscle mass (sic).”

That is to say, the rowers didn’t get buffer, but they did get tougher.

HMB isn’t a slam dunk like some other supplements, but it certainly interesting. As a aging athlete prone to self flagellation, I’ll probably give it a try at some point.

And, Todd and Patrick, if you’re still reading, because I mentioned you by name and spoke with THREE very fancy scientists to answer your question, it would be awesome if you shared this post in your social media. (Hint, hint.)