People used to think that bone, body fat, and other “structural” tissues are inert rather than metabolically active. The truth is that bone is incredibly plastic, responding to activity and nutrition, and that body fat is an endocrine organ in its own right, secreting hormones and shaping the way our metabolism works. What about cartilage? Can we do anything to improve its strength and function? (This Mark's Daily Apple article was written by Mark Sisson, and is narrated by Tina Leaman)