Chondroitin sulfate is a glycosaminoglycan formed naturally by the body for the synthesis and maintenance of connective tissue. Glycosaminoglycans, formerly termed mucopolysaccharides, are an integral component of all connective tissues. Connective tissues have various functions in the body. They support internal organs and connect bones to each other (ligaments), form bone, cartilage, and the walls of blood vessels, attach muscles to bones (tendons), and replace tissues that have been damaged. The two primary components of connective tissue are collagen and proteoglycans. Collagen is the strong, fibrous protein that physically connects our tissues. Proteoglycans are large carbohydrate-rich structures, resembling a bottle-brush in three-dimensional structure, i.e. a central protein rod with many strings of glucosamine-containing glycosaminoglycans extending outwards. Proteoglycans hold large amounts of water forming a stiff gel by virtue of their dense negative charges from sulfates. Proteoglycans link to collagen fibers to help form connective tissues. They provide resiliency, load distribution, shock-absorbing, compressive, and lubricating properties to connective tissues and joints. Chondroitin sulfate is supportive and protective of connective tissues in numerous ways. It is an excellent source of n-acetylgalactoaminoglycan for the synthesis and protection of proteoglycans associated with cartilage tissues. Chondroitin sulfate also protects existing cartilage by reducing water loss from the proteoglycan-formed gel and by inhibiting enzymatic breakdown of cartilage. It is not yet clear to what degree chondroitin sulfate is absorbed. Of concern is the size of the chondroitin sulfate molecule — in particular if it is too large to cross the intestinal lining. However, studies finding elevated plasma values of chondroitin sulfate following oral administration, in addition to studies demonstrating the benefits of orally administered chondroitin sulfate, support the bioavailability of this supplement.