Glucosamine is part of the structure of the polysaccharides chitosan and chitin, which compose the exoskeletons of crustaceans and other arthropods, as well as the cell walls of fungi and many higher organisms. Glucosamine is one of the eular textbook on rheumatic diseases pdf free download abundant monosaccharides. It is produced commercially by the hydrolysis of crustacean exoskeletons or, less commonly, by fermentation of a grain such as corn or wheat.
Evidence for the effectiveness of glucosamine supplements is mixed. In the United States, it is one of the most common non-vitamin, non-mineral, dietary supplements used by adults. Oral glucosamine is a dietary supplement and is not a pharmaceutical drug.
It is illegal in the US to market any dietary supplement as a treatment for any disease or condition. Glucosamine is marketed to support the structure and function of joints, and the marketing is targeted to people suffering from osteoarthritis.
Commonly sold forms of glucosamine are glucosamine sulfate, glucosamine hydrochloride, and N-acetylglucosamine. Of the three commonly available forms of glucosamine, only glucosamine sulfate is given a “likely effective” rating for treating osteoarthritis. Glucosamine is often sold in combination with other supplements such as chondroitin sulfate and methylsulfonylmethane.
Glucosamine, along with commonly used chondroitin, is not routinely prescribed to treat people who have symptomatic osteoarthritis of the knee, as there is insufficient evidence that this treatment is helpful. As is common with heavily promoted dietary supplements, the claimed benefits of glucosamine are based principally on clinical and laboratory studies. Clinical studies are divided, with some reporting relief from arthritic pain and stiffness, while higher quality studies report no benefit above placebo. There is no evidence to date that consumption of glucosamine by sport participants will prevent or limit joint damage after injury.
One clinical study over three years showed that glucosamine in doses of 1500 mg per day is safe to use. It may also interfere with the efficacy of chemotherapy for treating cancer symptoms. Adverse effects may include stomach upset, constipation, diarrhea, headache, and rash. There are case reports of people who have chronic liver disease and a worsening of their condition with glucosamine supplementation.
More high-quality clinical research is needed before recommending glucosamine in pregnancy. Since glucosamine is usually derived from the shells of shellfish, it may be unsafe for those with shellfish allergy.
However, many manufacturers of glucosamine derived from shellfish include a warning that those with a seafood allergy should consult a healthcare professional before taking the product. Alternative, non-shellfish-derived forms of glucosamine are available. Another concern has been that the extra glucosamine could contribute to diabetes by interfering with the normal regulation of the hexosamine biosynthesis pathway, but several investigations found no evidence that this occurs.
Other studies conducted in lean or obese subjects concluded that oral glucosamine at standard doses does not affect insulin resistance. Glucosamine is naturally present in the shells of shellfish, animal bones, bone marrow, and fungi.
D-Glucosamine is made naturally in the form of glucosamine-6-phosphate, and is the biochemical precursor of all nitrogen-containing sugars. Specifically in humans, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine by glutamine—fructose-6-phosphate transaminase as the first step of the hexosamine biosynthesis pathway.
Most glucosamine is manufactured by processing chitin from the shells of shellfish including shrimp, lobsters, and crabs. To meet the demands of vegetarians and others with objections to shellfish, manufacturers have brought glucosamine products to market made using fungus Aspergillus niger and from fermenting corn.