myHMB Science and
Clinical Research

This publication is the International Society of Sports Nutrition position stand on the efficacy of HMB use in sports nutrition and combines a comprehensive review of HMB with the official position of the ISSN on HMB use.  The position statements included in this paper were reviewed and approved by the Research Committee of the ISSN. Based upon this comprehensive review of HMB literature, the primary position statements were that HMB enhances muscle recovery by attenuating muscle damage; HMB increases muscle hypertrophy, strength, and power in trained and untrained populations when the appropriate exercise protocol is applied; HMB efficacy is manifested in young and old; and HMB is safe to consume.

Two groups of older men and women (> 65 years of age) were studied for 24 weeks.  One group was sedentary and one group underwent resistance training. Within each group participants were also randomized to either a placebo or HMB treatment. The researchers concluded that resistance training was an effective intervention for improving muscle strength and function in older adults, but may be of limited benefit in the population as a whole because of compliance issues.  The study also showed that HMB improves strength and muscle quality in sedentary older adults. Therefore, HMB may be a nutritional intervention to prevent sarcopenia in older adults.

In this study older men and women (average age ~67 years) were randomized to receive either HMB or placebo treatments during 10 days of bed rest.  While the placebo group lost lean body mass due to this period of inactivity, the HMB group maintained lean body mass. In conclusion, during at least a 10 day period of inactivity, HMB preserves lean body mass in healthy older adults.

Skeletal muscle protein turnover was measured in healthy young men in response to an oral dose of either 2.4 g of HMB in free acid form or 3.4 g of leucine. While both HMB and leucine stimulated muscle protein synthesis, HMB was also shown to attenuate muscle protein breakdown (-57%). The authors concluded that HMB induces anabolic effects in skeletal muscle that are distinct and/or additive to the effects of leucine.

The effects of HMB free acid supplementation and cold water immersion (CWI) on immune response after intense resistance training was studied in forty male subjects. Supplementation with HMB free acid reduced the pro-inflammatory cytokine TNF- immediately post exercise and its receptor expression (TNFR1) during the recovery period compared with placebo or CWI. The researchers concluded that HMB free acid may attenuate the immune response to resistance exercise which may then lead to reduced recovery time.

This study in trained athletes demonstrated that HMB free acid taken before a muscle-damaging, resistance-training session decreases muscle damage and improves perceived readiness to train in the next session. Thus, the athletes were able to recover quicker and train harder sooner with HMB free acid supplementation.

In this review of data from studies supplementing HMB, 13 studies in healthy trained individuals, 11 studies in healthy untrained individuals, and 9 studies in patients with chronic diseases were examined.  The authors concluded that these studies demonstrated the HMB was effective in preventing muscle damage after exercise in both trained and untrained individuals, as well as in preventing muscle loss during chronic disease.  Additionally, the authors described the safety profile of HMB supplementation as “unequivocal”.

This review discusses studies which have shown that HMB can improve protein turnover and attenuate muscle loss in the elderly and in the clinical setting.  The authors suggest a mechanism whereby HMB inhibits inflammation and muscle apoptosis in these populations, as well as improving protein synthesis and decreasing protein degradation, which results in increasing lean mass.

This paper reviews the mechanisms of action of HMB and discusses these in relation to the metabolic pathways causing cancer cachexia.  The authors conclude that based upon the available literature, HMB may be a potential nutritional component in therapies targeted to attenuate cancer cachexia.