It’s been about three decades since the first oral joint support supplement came on the market, a chondroitin sulfate product. This was followed by glucosamine (as a sulfate or chloride) and hyaluronic acid aka hyaluronate or hyaluronan. This is the big three of ingredients targeting joint metabolism and maintenance.
Glucosamine is a central player in the metabolism of all connective tissues, including joint cartilage. It is a precursor in the synthesis of both chondroitin sulfate and hyaluronic acid. Although normally very well tolerated, insulin levels should be monitored in horses with insulin resistance receiving glucosamine. This is not because it contains glucose but because metabolites of glucosamine can send the signal a cell is “full” of glucose and can reduce insulin’s ability to stimulate glucose uptake.
Chondroitin sulfate is the major structure in components called proteoglycans which give cartilage it’s ability to resist compression, primarily by holding water within the cartilage.
Hyaluronic acid is best known as the compound that gives joint fluid its slippery feel, reducing friction within the joint. It also forms a coat around each of the cells inside joint cartilage and binds with aggrecan to form a proteoglycan which, as above, holds water inside the cartilage to keep it plump and resistant to compression.
In addition to all their effects on the structure of cartilage and joint fluid, the big three also play important roles in cellular function. They are involved in:
- Synthesis of cartilage
- Synthesis of joint fluid
- Regulation of enzyme levels and activity
- Maintenance of bone structure under the cartilage
The most recent research has even uncovered nutrigenomic effects where there is interaction directly with the DNA to influence the health of the cartilage.
This is all very interesting but it doesn’t mean much if the glucosamine, chondroitin or hyaluronic acid are not absorbed when given orally. Early critics claimed they would surely be destroyed by stomach acid. However, studies have shown all three are in fact absorbed. Even better, attaching a radioactive label that allows researchers to track their location after absorption has shown these compounds become concentrated in the joints after absorption. Radioactive glucosamine is used in human medicine to map out areas of active arthritis because it reliably accumulates there.
Research has shown that glucosamine and chondroitin together works better than either one alone. Adding hyaluronic acid directly addresses levels of this key component of both cartilage and joint fluid.
While they don’t work miracles, supplementing these key nutrients provides hard working joints with added support to maintain normal structure and function.
Eleanor Kellon, VMD