VDR and sarcopenia: For example, both polymorphisms in the vitamin D receptor gene (Roth et al., 2004) and low serum vitamin D levels have been implicated in sarcopenia (Visser et al., 2003) and in increased myofibrillar protein degradation at younger ages (Wassner et al., 1983), suggesting that polymorphisms in the vitamin D receptor probably lead to its partial inactivation.