|Molecular formula||C10H18CaO6.H2O or C10H20CaO7|
|Molar mass||292.34 [g/mol]|
|Solubility in water||soluble|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Calcium β-hydroxy-β-methylbutyrate or calcium HMB is a nutritional supplement, which represents a calcium salt of beta-hydroxy beta-methylbutyrate (HMB). The latter is a leucine metabolite produced in the body through oxidation of the ketoacid of leucine (ketoisocaproate, KIC). Because leucine plays an important regulatory role in protein metabolism and due to the conversion of leucine to KIC, several researchers  have presumed that KIC was the active ingredient responsible for most of the beneficial effects of leucine on protein metabolism. In addition to its effects on protein metabolism, some studies demonstrated a major role for added leucine and leucine metabolites (HMB, β-hydroxy butyrate – BHB, β-hydroxy methyl glutarate – HMG) in modulating the immunocompetence cells, especially of lymphocyte activity. According to the results, the only direct leucine metabolite to affect lymphocyte blastogenesis was HMB.
Physical and chemical properties
Calcium beta-hydroxy beta-methylbutyrate, as a dietary supplement, may affect protein synthesis. During resistance training, calcium beta-HMB has been reported to reduce muscle catabolism, promote fat loss, increase strength and fat-free mass in athletic and nonathletic populations. However, it is less clear whether HMB supplementation promotes these adaptations in trained athletes. A study made by several scientists examined the effects of HMB (as the calcium salt) supplementation during resistance training (6.9±0.7 hr × wk(-1)) on markers of catabolism, body composition and strength in experienced resistance-trained males. In a randomized manner, 40 experienced resistance-trained athletes were matched and assigned to supplement their diet for 28 days with a fortified carbohydrate/protein powder containing either 0, 3 or 6 g × d(-1) of calcium HMB. Fasting venous blood and urine samples, dual energy X-ray absorptiometer-determined body composition, and isotonic bench press and leg press one repetition maximums (1 RM) were determined prior to and following 28 days of supplementation. The result of HMB supplementation was significant increases in serum and urinary HMB concentrations. However, the study demonstrated no statistically significant differences in general markers of whole body anabolic/catabolic status, muscle and liver enzyme efflux, fat/bone-free mass, fat mass, percent body fat, or 1 RM strength. Results indicate that 28 days of the use of HMB supplementation during resistance-training does not significantly reduce catabolism or affect training-induced changes in body composition and strength in resistance-trained males.
As to other possible benefits of calcium HMB, the supplement is proved to be an efficient phosphate binder in vitro, which may predict its effective role in vivo to treat such conditions as uremia.
Calcium beta-hydroxy-beta-methyl butyrate is of interest as a dietary supplement and a possible component of functional and medical foods. According to several studies on rats, CaHMB proved to be non-toxic and no adverse effects of this compound were observed.
According to a study in 2000, the subjects tolerated the supplementation protocol well with no reports of medical problems/symptoms in post-study questionnaires administered in a blinded manner. In addition, no significant medical complications were observed and/or treated by the athletic training staff during the study.
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- Baxter JH, Carlos JL, Thurmond J, Rehani RN, Bultman J, Frost D (December 2005). "Dietary toxicity of calcium beta-hydroxy-beta-methyl butyrate (CaHMB)". Food and Chemical Toxicology 43 (12): 1731–41. doi:10.1016/j.fct.2005.05.016. PMID 16006030.
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