HMB
A general hypothesis is proposed that HMB is metabolized to HMG-CoA in tissues such as muscle, mammary tissue, and certain immune cells and is used for de novo cholesterol synthesis, which would be harmful to health, increasing cholesterol levels. In times of stimulated growth and/or differentiation. HMG-CoA may be rate-limiting for cholesterol synthesis, which could limit cell growth or function. It is proposed that feeding HMB can provide a saturating source of cytosolic HMG-CoA for cholesterol synthesis and in turn allow for maximal cell growth and function. HMB is a bioactive metabolite of the branched-chain amino acid leucine. HMB has been shown to help maintain muscle function and support muscle growth, especially for those over 65. Vitamin D3 has well-documented benefits for muscle health and healthy bone density. Now, both ingredients are available in a single, convenient supplement.
Commercial comments from Life Extension company:
HMB for muscle protein balance and exercise performance: Skeletal muscle health requires a balance between anabolism (muscle growth) and catabolism (muscle breakdown). And as we age, we become more susceptible to anabolic resistance, where our body’s ability to build new muscle slows down, even in the presence of necessary amino acids.5,6
The result is a decline in muscle mass and strength. HMB has beneficial effects on muscle mass by helping to preserve the structural integrity of your muscles and supporting muscle growth.7,8 HMB also supports exercise performance during both resistance and endurance training.9-16
HMB in clinical studies: HMB and Bed Rest: Prolonged bed rest can result in loss of muscle mass. In a randomized placebo-controlled study, men and women were confined to bed rest for 10 days, followed by eight weeks of resistance training rehabilitation. Each group took either 3 g a day of HMB or a placebo for 5 days prior to bed rest, up until the end of the study. The placebo group lost lean mass during bed rest, but those given HMB during bed rest showed no such decline.17
HMB and Resistance Training: In a randomized, placebo-controlled trial, men and women received 3 g a day of HMB, or a placebo and trained for 4 weeks. At the end of the study, the HMB group had a greater increase in upper body strength than the placebo group.13 In another clinical study, supplementation with 3 g a day of HMB for 9 weeks provided a substantial benefit to lower-body strength when combined with resistance training.
HMB and Older Adults: In a 24-week, randomized, placebo-controlled study, adults 65 years and older were divided into an exercise group and a non-exercise group. Both groups took either 3 g of HMB twice a day or a placebo. The non-exercise group that took HMB showed signs of improved muscle health — but the exercise group’s results were even better, improving measurements of muscle function and lean mass.
