Calcium Hydroxymethyl Butyrate Monohydrate
Also known as: Calcium β-hydroxy-β-methylbutyrate, Ca-HMB, β-hydroxy-β-methylbutyrate, HMB, Hydroxymethylbutyrate
Overview
Calcium β-hydroxy-β-methylbutyrate (Ca-HMB), commonly known as HMB, is a metabolite of the amino acid leucine. It is naturally produced in the body and found in small amounts in foods like grapefruit, alfalfa, and catfish. HMB is often supplemented to build muscle, prevent age-related muscle loss, and enhance athletic performance. The calcium salt form (Ca-HMB) is frequently used to improve bioavailability and stability. Research on HMB is moderately mature, with several systematic reviews and meta-analyses available. However, the quality of evidence varies, with some studies showing significant effects, particularly in specific populations, while others find no significant benefits. Overall, the evidence quality is considered moderate to low due to inconsistencies and limitations in study designs.
Benefits
HMB may increase muscle mass and slow muscle loss in older adults, although it may not offer additional benefits beyond exercise alone. Some studies suggest HMB might reduce muscle catabolism, but this effect is not consistently observed, especially in trained athletes. There is limited evidence to support the use of HMB for improving athletic performance or resistance exercise-induced changes in body composition and strength in young or trained subjects. HMB may be beneficial for preventing age-related muscle loss (sarcopenia) and potentially improving muscle mass, but its effects on physical performance are unclear. A meta-analysis found no significant effects on lipid profiles with weighted mean differences (WMDs) that were not statistically significant.
How it works
HMB is believed to act through various pathways, including the mTOR pathway, which is involved in protein synthesis, and the PI3K/Akt pathway, which can influence muscle hypertrophy and reduce muscle catabolism. HMB may interact with muscle and metabolic systems to potentially enhance protein synthesis and reduce muscle breakdown. HMB can influence the expression of ubiquitin ligases and other proteins involved in muscle metabolism. The calcium salt form (Ca-HMB) is often used to enhance bioavailability and stability compared to the free acid form.
Side effects
HMB is generally considered safe when taken orally in doses up to 3 grams daily for up to one year. There are no commonly reported side effects at the recommended doses. No significant uncommon side effects have been reported. There is limited data on rare side effects, but none have been consistently reported. There is no substantial evidence of significant drug interactions. There is insufficient information to determine safety during pregnancy or breastfeeding, so it is advised to avoid use in these conditions. Caution is advised for pregnant or breastfeeding women due to the lack of data.
Dosage
Typical doses of HMB range from 2.4 to 3 grams per day, often in the form of Ca-HMB. Doses up to 3 grams daily have been used safely for up to one year. There is no specific timing recommendation, but it is often taken before or after exercise. The calcium salt form (Ca-HMB) is recommended for better bioavailability and stability. The absorption of HMB is enhanced when taken in its calcium salt form. There are no specific cofactors required for HMB supplementation.
FAQs
Is HMB effective?
HMB may be effective for preventing age-related muscle loss but has limited evidence for other uses.
Is HMB safe?
HMB is generally considered safe at recommended doses.
When should I take HMB?
No specific timing is recommended, but it is often taken in relation to exercise.
What results can I expect from taking HMB?
Expect small to no significant effects on muscle mass, strength, or lipid profiles in most populations.
Is HMB a potent muscle builder?
HMB is often misconceived as a potent muscle builder or performance enhancer, but the evidence is more nuanced.
Research Sources
- https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2024.1451282/full – This systematic review and meta-analysis of 10 RCTs with 421 adult participants found no significant effect of HMB supplementation on total cholesterol, triglycerides, LDL-C, and HDL-C. The quality of evidence was rated as moderate to low, and the review was conducted according to PRISMA guidelines and registered with PROSPERO.
- https://pubmed.ncbi.nlm.nih.gov/10606212/ – This randomized controlled trial involving 40 experienced resistance-trained males found no significant differences in markers of catabolism, body composition, or strength after 28 days of HMB supplementation. The study was double-blind and randomized, but the small sample size and specific population limit the generalizability of the findings.
- https://www.webmd.com/vitamins/ai/ingredientmono-45/hydroxymethylbutyrate-hmb – WebMD provides general information about Hydroxymethylbutyrate (HMB), including its uses, effectiveness, side effects, interactions, and precautions. It is a general overview and not a primary research article.
- https://www.mdpi.com/2072-6643/12/5/1523 – This study investigates the effects of HMB supplementation. Further details about the study design, population, and findings would be needed to provide a more comprehensive summary.
- https://www.sciencedirect.com/science/article/pii/S127977072301014X – This systematic review examined the effects of HMB on sarcopenia and functional frailty in older adults. The review found that HMB may increase muscle mass and slow muscle loss, but its effects on physical performance remain unclear due to heterogeneity in study designs and populations.