Muscle weakness and falls

Even if the muscle impairment secondary to hypovitaminosis D has been known since the seventeenth century in children affected by rickets, we had to wait for the discovery of the presence of the vitamin D receptor (VDR) in the human skeletal muscle cells to witness a remarkable growth of knowledge concerning the action of vitamin D on muscle. The effects of the binding of vitamin D to its receptor are (1) the stimulation of skeletal muscle growth and differentiation via gene transcription (long-term mechanism), (2) the activation of second messenger calcium-mediated system that regulates intracellular calcium levels and modulates muscle contraction (short-term mechanism), and (3) the inhibition of fat infiltration in skeletal muscle, thus improving physical performance. The prevalence of vitamin D deficiency increases with age contributing to muscle wasting and skeletal fragility. Therefore, along with the bone evaluation, a comprehensive assessment of skeletal muscle mass and functioning, including the measurement of appendicular lean mass (ALM) by dual-energy X-ray absorptiometry (DXA), muscle weakness by handgrip strength and knee extension strength, and physical performance through validated outcome measures, should be performed. Data about the efficacy of vitamin D or its derivatives in the improvement of skeletal muscle health are conflicting. The most relevant evidences regard the beneficial effects on muscle function and fall risk prevention. It has been demonstrated that vitamin D enhances the effectiveness of therapeutic interventions, such as exercise and dietary supplements, in terms of muscle strength and physical performance. Serum 25(OH)D levels should be higher than 30 ng/mL or higher than 40 ng/mL if we wish to improve muscle function. Therefore a supplementation of at least 2000 IU/day of vitamin D should be prescribed.

Even if the muscle impairment secondary to hypovitaminosis D has been known since the seventeenth century in children affected by rickets, we had to wait for the discovery of the presence of the vitamin D receptor (VDR) in the human skeletal muscle cells to witness a remarkable growth of knowledge concerning the action of vitamin D on muscle. The effects of the binding of vitamin D to its receptor are (1) the stimulation of skeletal muscle growth and differentiation via gene transcription (long-term mechanism), (2) the activation of second messenger calcium-mediated system that regulates intracellular calcium levels and modulates muscle contraction (short-term mechanism), and (3) the inhibition of fat infiltration in skeletal muscle, thus improving physical performance. The prevalence of vitamin D deficiency increases with age contributing to muscle wasting and skeletal fragility. Therefore, along with the bone evaluation, a comprehensive assessment of skeletal muscle mass and functioning, including the measurement of appendicular lean mass (ALM) by dual-energy X-ray absorptiometry (DXA), muscle weakness by handgrip strength and knee extension strength, and physical performance through validated outcome measures, should be performed. Data about the efficacy of vitamin D or its derivatives in the improvement of skeletal muscle health are conflicting. The most relevant evidences regard the beneficial effects on muscle function and fall risk prevention. It has been demonstrated that vitamin D enhances the effectiveness of therapeutic interventions, such as exercise and dietary supplements, in terms of muscle strength and physical performance. Serum 25(OH)D levels should be higher than 30 ng/mL or higher than 40 ng/mL if we wish to improve muscle function. Therefore a supplementation of at least 2000 IU/day of vitamin D should be prescribed.