chondroitin sulfate
Meaning of chondroitin sulfate: A long sugar chain bristling with negative charge, which drags in water and lets cartilage spring back after every step.
Definition of chondroitin sulfate
Chondroitin sulfate is a long unbranched chain built from a repeating pair of sugars, with sulfate groups attached along its length. It is the most abundant chain of its kind in cartilage, where great numbers of them are fixed to a protein core and hold water within the tissue. It occurs in bone, skin, blood vessel walls and the cornea too, and is sold as a joint supplement.
What does it do in cartilage?
It holds water, and the way it does so is mechanical. Sulfate groups give the chain a dense negative charge along its whole length, so neighboring chains push each other apart and pull water in between them. Hundreds of these chains stand out from a single protein core like the bristles of a bottle brush, and those brushes are anchored into a mesh of collagen. Weight on the joint squeezes water out of the mesh, the tissue flattens, and when the load lifts the charge draws the water straight back. Losing these chains is one of the earliest changes in a worn joint, and it is why cartilage that has thinned no longer recovers its shape.
Does swallowing it repair a joint?
The evidence has not supported the simple version of that idea. A chain this large is broken into fragments in the gut, so what is absorbed is not the intact molecule that was swallowed, and there is no mechanism carrying those fragments to a particular joint. Large trials of the supplement, alone and paired with glucosamine, have mostly found no clear advantage over placebo for knee pain overall, while some analyses report a modest effect and the results continue to conflict. Preparations are made from cattle windpipe or shark cartilage and vary in content between brands.
How does it compare with related chains?
| Chain | Where it concentrates | Distinguishing feature |
|---|---|---|
| Chondroitin sulfate | Cartilage, bone, cornea, vessel walls | The most abundant of them in cartilage |
| Keratan sulfate | Cartilage and cornea | Sits on the same protein core alongside it |
| Hyaluronan | Joint fluid and skin | Carries no sulfate and no protein core |
| Heparan sulfate | Cell surfaces and basement membranes | Kin to the anticoagulant heparin |
All belong to the group called glycosaminoglycan. The family resemblance to heparin is the reason a bleeding risk is raised when the supplement is taken alongside drugs that thin the blood. Inherited faults in the enzymes that dismantle these chains cause them to pile up inside cells, producing the group of childhood disorders known as the mucopolysaccharidoses.
Also known as
Used in a sentence
Chondroitin sulfate content of the cartilage matrix was reduced in the affected joint.
Good to know
The molecule is broken up during digestion, so swallowing it does not deliver the intact chain to cartilage, and its structural kinship with heparin is the basis of the bleeding concern raised alongside blood-thinning drugs.
Word origin
Where “chondroitin sulfate” comes from
From the Greek chondros, meaning cartilage or gristle, with sulfate naming the groups attached along the chain.