What is HMB?

But what exactly is it? If you’re wondering whether HMB might be what you’re looking for, we’ve asked our in-house sports nutrition expert Emily Foster what it is, what it does and any side effects to look out for.

HMB or Beta-Hydroxy Beta-Methylbutyrate is a chemical that’s made when your body breaks down an amino acid called leucine. HMB rolls off the tongue a little easier, so you’ll likely see it called this on the shelves, on social media and online.

To understand HMB, let’s refresh ourselves on some protein basics. Amino acids are the building blocks of protein and – of the 20 amino acids – the important one to remember here is leucine,¹ Leucine along with other amino acids form a protein, which are important to maintain and build muscle.²

“Leucine triggers the process of muscle protein synthesis. This signals the muscle cells to make new muscle proteins. This regeneration is good for building muscle and strength,” says Emily. 

When your body processes the amino acid, leucine,³ small amounts of HMB are naturally produced by your body, so you may not need to supplement it. However, some people choose to take it as supplement for a range of potential benefits.⁴

Given that it’s a by-product of leucine (the amino acid that directly stimulates muscle protein synthesis) it’s thought that HMB may help to reduce or prevent the breakdown of muscle.^5-7 A published paper analysed several clinical studies on the role of HMB on different types of physical performance and concluded it may reduce post exercise muscle damage.⁵ Thus, research is still on-going and further studies looking into the potential benefits of HMB in large healthy populations is one of the next steps in future research.⁷

As with any supplement, it’s essential to proceed with caution when adding HMB to your routine. While research is underway, it’s not always clear how taking new supplements will interact with the body. If you have any concerns, it’s best to speak to your doctor first.

“Creatine increases the body’s production of phosphocreatine, which is the source of energy the body uses for short, intense bursts of activity,” explains Emily. “This means that it can help your muscles produce energy during heavy lifting or high intensity exercise, such as sprints or jumps. It’s found in meat and fish, but lots of sport and fitness enthusiasts take creatine supplements.”

Your body can produce it using the amino acids glycine and arginine.¹³A popular supplement among athletes who seek to improve sport and exercise performance and speed up recovery.

Creatine is mostly known to increase physical performance in successive bursts of short-term, high intensity exercise and support muscle growth, while HMB helps to prevent muscle breakdown and support recovery after intense exercise.¹⁴

“While there isn’t currently any evidence to suggest that the two together will achieve better results, in theory they could possibly support different areas of your workout. Follow the instructions on the supplement, but creatine could support your pre-workout, while HMB comes into play afterwards,” says Emily.

As long as you are taking the suggested dosage and are being sensible with your supplements, most people can take HMB with others. However, if you are unsure or take any existing medication please speak to your doctor before taking HMB.

Generally, HMB is safe to take daily and for some it’s hard to get it through diet alone – especially as it’s found in unusual foods like grapefruit and catfish.¹⁰

On the whole, it’s thought that HMB is a reasonably safe supplement for most people.¹⁴ But it’s always a good idea to talk to your doctor before taking it, especially if you are on medication.

While clinical studies haven’t revealed concerning side effects, it’s also worth remembering that this doesn’t mean there aren’t any.^10,17

If you notice any unwanted symptoms when taking HMB, stop using your supplement and speak to your doctor about your concerns.

So, to recap, HMB has been studied for muscle strength, gains and performance. ^8-10

And as long as you’re sensible with your supps and the suggested dose, HMB is safe to take alongside your other daily vitamins – but make sure you check with your doctor if you have any concerns.

Whether you’re wondering how protein supports your sports goals or how to gain muscle safely, look out for our expert-lead exercise and sports nutrition features.