Effects of a Supplement Enriched in Hydroxymethylbutyrate and Vitamin D on Muscle Strength in Hip Fracture

Hip Fractures

Hip fractures, Ageing, Sarcopenia, Function

The purpose of this study is to determine whether a nutritional supplement high in protein and energy, and enriched with hydroxymethylbutyrate (HMB) and vitamin D is more effective than a standard nutritional supplement high in protein and energy in improving muscle strength in elderly patients with hip fracture.

Hip fractures are the cause of substantial morbidity and mortality in elderly people. Nine months after hip fracture, patients still have a poorer quality of life compared to control subjects matched for age and sex. After a hip fracture, many patients fail to return to their homes and their previous state of mobility. Acute hospital costs generated by this condition are substantial, although the costs in rehabilitation and special care in long-term community are even greater. Patients with hip fracture are most likely to be frail elderly, and they are usually malnourished when the fracture occurs. Moreover, physiological aging is accompanied by functional losses and changes in the various organs and systems, including the musculoskeletal system, in which there is a progressive reduction of muscle mass, called sarcopenia. Approximately 30% of muscle mass is lost between the fifth and eighth decades of life and the percentage of muscle loss can reach 15% per decade after 70 years of age. Having established a correlation between the loss of muscle mass and loss of strength, sarcopenia has been associated with a risk of functional disability twice in men and thrice in women. Hydroxymethylbutyrate (HMB) is a leucine metabolite produced in small quantities (0.3-0.4 g/d). Leucine effects on muscle metabolism appear to be due, in part, to HMB. In vitro experiments have observed that HMB attenuates proteolysis processes through the inhibition of various catabolic pathways and could stimulate protein synthesis. There are some evidences that administration of HMB in the elderly results in increases in muscle strength and functionality enhancements, compared to a control group. In elderly people, low levels of vitamin D have been associated, among others, to decreased muscle strength, falls and fractures. The elderly have an increased risk of developing vitamin D deficiency due to less sun exposure, a decrease in the absorption and changes in the metabolism of this vitamin. Because muscle weakness is a clinical feature of vitamin D deficiency, it has been postulated that its deficiency could precipitate and increase muscle weakness and functional decline in older people. Therefore, the study raises the possibility that an intervention consisting of a high protein, high calorie oral nutritional supplement enriched with HMB and vitamin D is more effective than a standard high protein, high calorie oral nutritional supplement in improving muscle strength.

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