ISSN updates position on HMB for muscle health based on new research findings

The International Society of Sports Nutrition (ISSN) has published an updated Position Stand on HMB (β-Hydroxy-β-Methylbutyrate) to recognize the booming scientific research on the muscle health ingredient.

Reviewed by ISSN’s Research Committee, Position Stands are comprehensive, evidence-based papers that review research sources behind certain ingredients, such as HMB, protein, caffeine and creatine. 

“The volume of research has increased exponentially since the last Position Stand was published in 2013,” says author John A. Rathmacher, Ph.D., director of Clinical Research and Laboratory Services at MTI BioTech. 

“Now there are two to three papers a month related to HMB, focusing on everything from the mechanism of action to newer publications on its benefits for older adults and aging athletes, mitigating muscle loss and its positive impact on muscle function and strength.”

HMB Position Stand

ISSN’s Research Committee approved 12 points about HMB regarding its effects, safety, mode of action and health benefits. 

The paper published in the Journal of the International Society of Sports Nutrition details that HMB is a metabolite of the amino acid leucine naturally produced in humans and other animals. The research covers two forms of HMB: Calcium HMB (HMB-Ca) and a free acid form of HMB (HMB-FA). 

“HMB-FA appears to lead to increased appearance of HMB in the bloodstream when compared to HMB-Ca, though recent results are mixed,” reads the paper. 

Both HMB forms are safe for oral supplementation in humans for up to one year. Research finds no adverse effects of HMB-CA and HMB-FA on human glucose tolerance and insulin sensitivity. Moreover, HMB may be connected to improvements in glucose metabolism in younger adults. 

The researchers explain that HMB’s primary mode of action “appears to be through its dual mechanism to enhance muscle protein synthesis and suppress muscle protein breakdown. HMB’s activation of mTORC1 is independent of the leucine-sensing pathway.”

Health benefits

The ISSN Position Stand covers various muscle health and exercise performance benefits based on existing research. 

For example, HMB may help reduce muscle damage and promote muscle recovery, promoting muscle growth and repair. HMB may also have anti-inflammatory effects, which could contribute to reducing muscle damage and soreness.

When consumed close to an exercise, HMB may improve muscle protein synthesis and attenuate the inflammatory response. It is linked to beneficial physiological effects in acute and chronic consumption. 

The expert author group reviewed a database of over 750 scientific references to HMB for the updated Position Stand.The paper adds: “Daily HMB supplementation at 38 mg/kg body weight in combination with exercise training may potentially improve body composition through increasing lean mass and/or decreasing fat mass with benefits in participants across age, biological sex and baseline training status. The most pronounced improvements in body composition with HMB have been observed in studies with robust resistance training programs and dietary control.”

Results on HMB’s performance benefits in trained athletes are mixed but are more extensive in studies over six weeks. However, the ingredient may improve strength and power in untrained individuals, likely driven by improved recovery. 

Research suggests that HMB supplementation may positively impact aerobic performance in trained athletes, although the proposed mechanisms of the effects are unknown.

HMB also has potential in healthy aging, as it can be important to improve muscle strength, functionality and muscle quality in a non-exercising, sedentary and aging population. Though its effects with exercise are varied, this combination may benefit the treatment of age-associated sarcopenia. 

The ingredient can also help counter muscle disuse atrophy during periods of inactivity for people suffering from illness or injury. Research points to the modulation of mitochondrial dynamics and lipid metabolism as a potential mechanism of action beyond HMB’s effects on muscle protein synthesis and degradation. 

In addition, HMB efficacy may be enhanced by combining it with certain nutrients under select conditions. For example, when HMB is co-administered with the amino acids glutamine, arginine and lysine, its effect on lean body mass may increase. 

Ongoing research

The expert author group reviewed a database of over 750 scientific references to HMB for the updated Position Stand, which included research studies, original articles and reviews. These references are resources for consumers, sports nutritionists and dietitians to help them understand the science behind ingredients. 

Rathmacher says: “A lot of data has emerged over the last ten years demonstrating HMB’s synergies with other ingredients, including creatine, vitamin D, protein and certain amino acids, to both help address muscle loss and improve overall muscle health.”

Recent and upcoming research points to the ingredient’s versatility. For example, Rathmacher says clinical studies are underway on older adults in the US and other countries to assess HMB’s potential in healthy aging. 

“I can also see the value in research focusing on HMB’s ability to counter muscle atrophy due to disuse, whether in injured athletes who are starting to lose muscle mass or in seniors due to knee replacements.”