Glucosamine is a naturally occurring sugar, a glucose molecule with an amino (NH2) group substituted for a hydroxyl group on the second carbon atom. This molecule is found abundantly in nature and is an essential building block of chitin, bacterial cell walls, extracellular matrix and cartilage. Supplementation with glucosamine has been useful in promoting healthy joints as demonstrated in various studies and recently in the Archives of Internal Medicine (1).

A question arises for those people with blood sugar problems. How will glucosamine influence blood sugar and insulin levels? Several animal and in-vitro cell line experiments have suggested that glucosamine can lead to insulin resistance, a condition in which cells no longer respond properly to insulin (2). One theory to explain this potential effect involves the hexosamine pathway. Glucose is broken down for energy by a process called glycolysis. One of the intermediate compounds in this pathway is fructose-6-phosphate. Under normal conditions, a very small amount of this compound reacts with glutamine, an amino acid, and the enzyme glutamine fructose-6-phosphtate amidotransferase (GFAT) to form glucosamine-6-phosphate (3). The theory is that increased glucosamine-6-phosphate levels in the cell would signal the cell that there is too much glucose and would shut down the cell's response to insulin. The theory suggests that supplementation with glucosamine would accelerate this normal process by increasing the cellular levels of glucosamine-6-phosphate so that when stimulated by insulin, cells (thinking that they already had too much glucose) would respond slowly, if at all (4).

A few human studies have examined this issue. Monauni et al. found that even though glucosamine infusion did not affect readily releasable insulin levels, glucose stimulated insulin secretion (GSIS), the time constant of secretion, glucose utilization or intracellular metabolism, it may have had a negative impact on plasma fasting glucose levels (5). Pouwels, et al., using a similar technique, found that glucosamine had no effect on insulin-induced glucose uptake (6). A 3-year study on the effectiveness of glucosamine sulfate on osteoarthritis found that oral glucosamine supplementation actually tended to decrease fasting glucose levels (7). A recent rat experiment shows that in rats susceptible to sugar-induced insulin resistance, oral glucosamine supplementation for 9 weeks did not cause insulin resistance (8).

While some studies indicate a potential for glucosamine to be disruptive of proper glucose metabolism and insulin response, other studies produce contradictory findings and suggest that more research is needed before a final conclusion can be made in regards to oral glucosamine supplementation and insulin resistance in humans.

In the meantime, people with insulin resistance or potential problems for blood sugar control may want to have their blood glucose and insulin levels monitored while taking glucosamine. Additionally, those people with shellfish allergies should avoid glucosamine supplements as they are sourced from shellfish. Alternatives to glucosamine include:

• ArthRed™, available in both capsules and powder, is a source of hydrolyzed bovine cartilage peptides and is 97% protein
• MSM, a sulfur-containing compound
• Boswellia,an herb that has been shown to support joint comfort
• EPA/DHA essentials, an essential fatty acid supplement that may promote joint comfort