HMB

HMB, or beta-hydroxy-beta-methylbutyrate, is a compound the body makes from leucine, one of the essential amino acids. It has been researched for more than 25 years for its relationship with muscle protein turnover.

What is HMB?

When the body metabolises leucine, only about 5% is converted into HMB. To get the 3 g a day used in studies from food, you would need to eat about 60 g of leucine, an amount a normal diet does not reach.

In supplements it is used mainly as the calcium salt (Ca-HMB), the form most used in clinical research. When reading labels and studies, check whether the dose is expressed as Ca-HMB or HMB, as the figures are not equivalent: in Muscle Guard, 3.9 g of Ca-HMB (myHMB®) provides 3 g of HMB.

How does it work?

• Protein turnover: muscle renews itself continuously, making new proteins while others are broken down. In a human metabolic study, a dose of HMB increased muscle protein synthesis and reduced its breakdown in the following hours (Wilkinson 2013).
• Synthesis signals: it activates the mTOR pathway, one of the main cellular routes that switch on protein production, in a similar way to leucine.
• Muscle breakdown: it has been described as moderating the activity of the ubiquitin-proteasome system, one of the pathways muscle uses to break down proteins.

What does the science say?

Older adults

A meta-analysis of trials in older adults found greater preservation of muscle mass with HMB than with placebo (Wu 2015). Results depend on context: age, diet, activity level and starting point all influence the response.

Periods of inactivity

In a trial with older adults on 10 days of bed rest, those who took 3 g of Ca-HMB a day lost less lean mass than the placebo group (Deutz 2013). It is a small study, so the result needs to be confirmed in larger trials.

People already doing strength training

In young people who train, a meta-analysis found no additional improvements in strength or body composition when HMB was added to training (Jakubowski 2020). When there is a strong, regular training stimulus, there is less room for improvement.

Dose and how to take it

• The dose most used in studies is 3 g of HMB a day, about 38 mg per kg of body weight (Wilson 2013).
• There is no solid evidence that one time of day is better than another: what matters is taking it consistently.
• Muscle Guard provides the 3 g of HMB in a single stick a day, together with 1 g of taurine and vitamins D3 and K2.

Safety

• In clinical trials, HMB has been well tolerated at 3 g a day, including in long-term studies (Nissen 2000).
• There is not enough data in pregnancy and breastfeeding. Muscle Guard should not be taken during pregnancy.
• If you have kidney disease, are under medical treatment or take several medicines, check with your healthcare professional first.

Frequently asked questions

Is HMB the same as leucine?

No. HMB is a product of leucine metabolism. Leucine is an amino acid that forms part of proteins; HMB is formed from it in small amounts.

HMB or creatine?

They do not have the same goal. Creatine is well studied in short, high-intensity efforts, while HMB has been researched mainly in preserving muscle mass in situations with a higher risk of loss. They can be taken together.

Does HMB replace protein?

No. Protein provides the amino acids muscle needs to renew itself; HMB, when used, complements a diet with enough protein and strength exercise. We explain it in more detail in our article HMB: what it is, what it does and when it can help.

References

1. Wilkinson DJ, Hossain T, Hill DS, et al. Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism. J Physiol. 2013;591(11):2911-2923.
2. Wu H, Xia Y, Jiang J, et al. Effect of beta-hydroxy-beta-methylbutyrate supplementation on muscle loss in older adults: a systematic review and meta-analysis. Arch Gerontol Geriatr. 2015;61(2):168-175.
3. Deutz NE, Pereira SL, Hays NP, et al. Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults. Clin Nutr. 2013;32(5):704-712.
4. Jakubowski JS, Nunes EA, Teixeira FJ, et al. Supplementation with the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) does not improve resistance exercise-induced changes in body composition or strength in young subjects: a systematic review and meta-analysis. Nutrients. 2020;12(5):1523.
5. Wilson JM, Fitschen PJ, Campbell B, et al. International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB). J Int Soc Sports Nutr. 2013;10(1):6.
6. Nissen S, Sharp RL, Panton L, et al. β-hydroxy-β-methylbutyrate (HMB) supplementation in humans is safe and may decrease cardiovascular risk factors. J Nutr. 2000;130(8):1937-1945.