Although glucosamine was initially thought to act as a substrate of collagen, this theory has since been discredited. Instead, it appears that glucosamine interferes with the inflammatory cascade involved in the degradation of collagen in arthritic tissues by downregulating the collagen-deteriorating effects of pro-inflammatory molecules, such as interleukin 1 (IL-1).[1]
Another proposed mechanism observed in vitro is that glucosamine sulfate increases collagen expression by promoting the synthesis of glycosaminoglycans. However, it’s important to specify that the concentrations used in this research were high and may not be directly applicable to human oral consumption.[2] Additionally, clinical studies attempting to measure a serum biomarker of collagen synthesis, type II collagen synthesis (CPII), did not observe a significant effect from glucosamine treatment.[3][4]