Hydroxymethyl butyrate as a therapeutic supplement
Hydroxymethyl butyrate (HMB), also known as beta-hydroxy-beta-methylbutyric acid, is a natural compound produced in the human body during the breakdown of the amino acid leucine, which is abundant in muscle tissue. It has gained attention as a therapeutic supplement primarily for muscle building and recovery, especially among athletes and bodybuilders. Some studies suggest that HMB supplementation may help reduce muscle tissue breakdown, enhance recovery after intense exercise, and improve muscle function in older adults, although research findings have been mixed and often lack large-scale studies.
HMB is available in powder or pill form, typically requiring a dosage of 1 to 3 grams daily for therapeutic effects. While it can be found in small amounts in various foods like dairy products, citrus fruits, and fish, sufficient therapeutic levels are generally achieved through supplementation. It is often included in protein powders aimed at stimulating muscle growth and combating age-related muscle loss, particularly for individuals aged sixty and older.
Although HMB appears to be safe at recommended doses, it is not regulated for safety by the FDA, and users are encouraged to seek third-party evaluations for product quality. While some evidence suggests potential benefits for muscle strength and recovery, especially for those new to exercise, the overall efficacy of HMB for enhancing muscle mass and strength in younger adults remains uncertain. Further research is needed to clarify its effects and safety, particularly for diverse populations.
Hydroxymethyl butyrate as a therapeutic supplement
DEFINITION: Natural substance of the human body used as a supplement to treat specific health conditions.
PRINCIPAL PROPOSED USE: Muscle building for strength in athletes and bodybuilders
OTHER PROPOSED USE: Enhancing recovery from heavy exercise and aiding muscle function in older adults
Overview
Technically called beta-hydroxy-beta-methylbutyric acid, the chemical hydroxymethyl butyrate (HMB) is found naturally in the human body when the amino acid leucine breaks down. Leucine is found in particularly high concentrations in muscles. During athletic training, damage to the muscles leads to the breakdown of leucine and increased HMB levels.
Evidence suggests that taking HMB supplements might signal the body to slow down the destruction of muscle tissue. However, while promising, the research record is contradictory and marked by an absence of large studies.
Requirements and Sources
HMB is not an essential nutrient, so there is no established requirement. HMB is found in small amounts in citrus fruit, dairy products, cauliflower, alfalfa, grapefruit, and catfish. To get a therapeutic dosage, however, individuals need to take a supplement in powder or pill form. In supplements, the ingredient may be listed as Beta-hydroxy beta-methylbutyric free acid (HMB-FA) or Beta-hydroxy beta-methylbutyrate monohydrate (HMB-Ca or Ca-HMB). Choosing a supplement with a credential from a third-party evaluator like the United States Pharmacopeia (USP) is recommended by some medical professionals, but HMB supplements are not evaluated by the Food and Drug Administration for safety.
Therapeutic Dosages
A typical therapeutic dosage of HMB is between 1 and 3 grams (g) daily. One should not confuse HMB with gamma hydroxybutyrate (GHB), a similar supplement. GHB can cause severe sedation, especially when combined with other sedating substances, such as alcohol or antianxiety drugs.
Therapeutic Uses
After age thirty, human bodies lose between 3 and 8 percent of their muscle mass every ten years. HMB is often included in protein powder beverage mixes and supplements to stimulate cell growth and reduce natural muscle loss. Additionally, adults over age sixty need around twice as much leucine to build and maintain muscle because the body's ability to metabolize amino acids decreases with age, which causes levels of HMB to decrease.
For younger adults and bodybuilders, HMB is more effective at muscle recovery when combined with other supplements like creatine. HMB’s impact is most evident in young individuals who are new to exercise or strength training. However, the overall results of a review of fourteen clinical studies failed to find evidence of the significant benefit of HMB in individuals under forty-five. Notably, most studies primarily focus on men, so findings may not apply equally to all individuals.
According to some small double-blind trials, HMB may improve response to weight training. One small double-blind, placebo-controlled trial found hints that HMB might help prevent muscle damage during prolonged exercise, potentially enhancing recovery during athletic training; however, a follow-up study failed to find this benefit. A small study found evidence that HMB might improve aerobic exercise capacity. Weak evidence suggests that HMB might improve blood pressure and cholesterol levels.
Scientific Evidence
In a controlled study, forty-one male volunteers, nineteen to twenty-nine years old, were given either 0 g, 1.5 g, or 3 g of HMB daily for three weeks. The participants also lifted weights three days a week for ninety minutes. The results suggest that HMB can enhance strength and muscle mass in direct proportion to intake.
In another controlled study reported in the same article, thirty-two male volunteers took either 3 g of HMB daily or placebo and then lifted weights for two or three hours daily, six days a week for seven weeks. The HMB group saw a significantly greater increase in its bench-press strength than the placebo group. However, there was no significant difference in body weight or fat mass by the end of the study. Similarly, a double-blind, placebo-controlled trial of thirty-nine men and thirty-six women found that within four weeks, HMB supplementation improved response to weight training.
Two placebo-controlled studies in women found that 3 g of HMB had no effect on lean body mass and strength in sedentary women, but it did provide an additional benefit when combined with weight training. In addition, a double-blind study of thirty-one men and women, seventy years old, undergoing resistance training found significant improvements in fat-free mass attributable to the use of HMB (3 g daily). However, other small studies have found marginal or no benefits of HMB in enhancing body composition or strength.
When the results of small studies contradict one another, it often means that the studied treatment produces minimal benefits at most, which may be the case with HMB. Larger trials are necessary to determine the extent of its effect. Trials continued on HMB into the twenty-first century, focusing on the impact on body composition, muscle growth, and reduced muscle breakdown in various populations.
Studies continued to show mixed results regarding HMB’s effect on muscle growth in older populations or athletes supplemented with HMB. Studies did, however, show HMB has the potential to preserve muscle mass in patients with health conditions that cause muscle deterioration, such as HIV and cancer. Benefits were also seen in exercise adaptation, anti-inflammatory properties, and cholesterol-lowering. Further studies began to support the use of HMB supplements for muscle function, strength, and some cognitive functions in older adults and individuals experiencing malnutrition. With exercise, HMB also showed evidence of improving sarcopenia, a musculoskeletal disease. In a review of ten large-scale randomized-controlled studies concerning the benefits of HMB for older adults, results were positive in most studies with few side effects. An additional review of nine similar studies confirmed this finding. Though more research is needed, some research indicates HMB improves learning and memory.
Safety Issues
HMB seems to be safe when taken at standard doses. Clinical trials have not found any significant adverse effects with short-term HMB use. Short- and long-term toxicological studies in animals have also found no evidence of harm. However, full safety studies have not been performed, so HMB should not be used by young children, pregnant or nursing women, or those with severe liver or kidney disease, except on the advice of a physician.
As with all supplements taken in very large doses, it is important to purchase a quality product, as an impurity present even in very small percentages could add up to a real problem.
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