The effect of glucosamine on glucose metabolism in humans: a systematic review of the literature.

OBJECTIVE Glucosamine is commonly used for the treatment of osteoarthritis. It is available as an over the counter preparation and also as a prescription pharmaceutical. There is concern from animal experiments that glucosamine may alter glucose metabolism through the hexosamine biosynthetic pathway. The objective of this systematic review is to determine if exogenous glucosamine adversely affects glucose metabolism in humans. This review does not separate out the effects on glucose metabolism of the various glucosamine preparations. METHOD An English-language literature search of MEDLINE, EMBASE and EBM Reviews (1950-February 2009) was conducted. The bibliographies of selected papers were manually searched for additional references. Two reviewers independently analyzed studies for quality and content using a standardized data extraction form. RESULTS Eleven studies were included. Six studies were randomized controlled trials and the remaining five were prospective studies with or without controls. Four of the studies found decreased insulin sensitivity or increased fasting glucose in subjects taking glucosamine. Three of these were clinical studies using oral glucosamine. Studies that included subjects with baseline impaired glucose tolerance or insulin resistance were more likely to detect an effect on glucose metabolism than studies without such subjects. CONCLUSION Clinical studies, including three using oral glucosamine, have provided mixed evidence about the effect of exogenous glucosamine on glucose metabolism in humans. Therefore, more studies are needed, particularly including subjects at high risk for impairments in glucose homeostasis, before a definite conclusion can be made.