- Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged > or =60 y. Bischoff-Ferrari, H.A., Dietrich, T., Orav, E.J., Hu, F.B., Zhang, Y., Karlson, E.W., Dawson-Hughes, B. Am. J. Clin. Nutr. (2004)