Food Allergy Nutrition

by bnpositive

Biochemistry

Glucosamine was first prepared in 1876 by Dr. Georg Ledderhose by the hydrolysis of chitin with concentrated hydrochloric acid. The stereochemistry was not fully defined until the 1939 work of Walter Haworth. D-Glucosamine is made naturally in the form of glucosamine-6-phosphate, and is the biochemical precursor of all nitrogen-containing sugars. Specifically, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine as the first step of the hexosamine biosynthesis pathway. The end-product of this pathway is UDP-N-acetylglucosamine (UDP-GlcNAc), which is then used for making glycosaminoglycans, proteoglycans, and glycolipids.

As the formation of glucosamine-6-phosphate is the first step for the synthesis of these products, glucosamine may be important in regulating their production; however, the way that the hexosamine biosynthesis pathway is actually regulated, and whether this could be involved in contributing to human disease remains unclear.

Indications

Oral glucosamine is marketed as a treatment of osteoarthritis. Commonly sold forms of glucosamine are glucosamine sulfate and glucosamine hydrochloride. Glucosamine is often sold in combination with other supplements such as chondroitin sulfate and methylsulfonylmethane.

Glucosamine may take weeks to months before improvements in symptoms are noticed.

Restoration of cartilage

A 2009 review concluded that “Little evidence suggests that glucosamine is superior to a placebo treatment in restoring articular cartilage.”

Osteoarthritis pain

A 2009 scientific review of available studies concluded that glucosamine sulfate, glucosamine hydrochloride, and chondroitin sulfate have individually shown inconsistent efficacy in decreasing OA pain, but many studies confirmed OA pain relief with glucosamine and chondroitin sulfate in combined use.

Health effects

Since glucosamine is a precursor for glycosaminoglycans, and glycosaminoglycans are a major component of joint cartilage, supplemental glucosamine may help to prevent cartilage degeneration and treat arthritis. Its use as a therapy for osteoarthritis appears safe, but there is conflicting evidence as to its effectiveness. A Cochrane 2005 meta-analysis of glucosamine for osteoarthritis found that only “Rotta” preparations (including older studies) found beneficial effects for pain and functional impairment. It also found that when only the studies using the highest-quality design were considered, there was no effect above placebo. In addition, in vitro analysis of glucosamine has revealed that glucosamine inhibits cartilage cell characteristics. Studies reporting beneficial effects have generally used glucosamine sulfate. Chondroitin sulfate is sometimes used in conjunction, and animal studies suggest that chondroitin may increase its efficacy. Two recent randomized, double-blind controlled trials have found no effect beyond placebo in reducing pain, while one found an effect beyond placebo.

Use

A typical dosage of glucosamine salt is 1,500 mg per day. Glucosamine contains an amino group that is positively charged at physiological pH. The anion included in the salt may vary. The amount of glucosamine present in 1500 mg of glucosamine salt will depend on which anion is present and whether additional salts are included in the manufacturer’s calculation. Glucosamine and chondroitin are “apparently poor candidates for transdermal [through the skin] absorption”, but glucosamine’s metabolite N-acetyl-D-glucosamine (NAG) appears to be a better candidate. The ability of NAG to permeate the skin is enhanced by ethanol and dimethyl sulfoxide (DMSO). DMSO is used to help deliver drugs in veterinary care, but is not approved for use on humans.

Glucosamine is a popular alternative medicine used by consumers for the treatment of osteoarthritis. Glucosamine is also extensively used in veterinary medicine as an unregulated but widely accepted supplement.

Contraindications

Clinical studies have consistently reported that glucosamine appears safe.

Allergy

Since glucosamine is usually derived from shellfish, those allergic to shellfish may wish to avoid it; however, since glucosamine is derived from the shells of these animals while the allergen is within the flesh of the animals, it is probably safe even for those with shellfish allergy. Alternative sources using fungal fermentation of corn are available.

Some commercially sold glucosamine supplements have other questionable ingredients added such as chinese skullcap, in addition to the more typical chondroitin, and MSM which is often seen too. “Allergic” type reaction may well be to these other ingredients and not the shellfish. People with reactions to these concoctions should also look at such things as red dyes and other needless additives. As noted above, the shellfish warning is just that warningresumably done by the lawyers and not because of a real problem.[citation needed] First hand experience with these since they first appeared in the USA has shown that the “red” pills are much more likely to cause a reaction, and the white ones do not unless chinese skullcap or other herbal additives are also included.[original research?]

Glucose metabolism

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 have found no evidence that this occurs. A review conducted by Anderson et al. in 2005 summarizes the effects of glucosamine on glucose metabolism in in vitro studies, the effects of oral administration of large doses of glucosamine in animals and the effects of glucosamine supplementation with normal recommended dosages in humans, concluding that glucosamine does not cause glucose intolerance and has no documented effects on glucose metabolism. It should be mentioned that the authors of the above mentioned review paper (Anderson et. al.) were financially supported by Cargill, Incorporated, Eddyville, IA, a manufacturer of glucosamine as mentioned in the acknowledgments section of the paper. Other studies conducted in lean or obese subjects concluded that oral glucosamine at standard doses does not cause or significantly worsen insulin resistance or endothelial dysfunction.

Legal status

United States

In the United States, glucosamine is not approved by the Food and Drug Administration for medical use in humans. Since glucosamine is classified as a dietary supplement in the US, safety and formulation are solely the responsibility of the manufacturer; evidence of safety and efficacy is not required as long as it is not advertised as a treatment for a medical condition. The U.S. National Institutes of Health is currently conducting a study of supplemental glucosamine in obese patients, since this population may be particularly sensitive to any effects of glucosamine on insulin resistance.

Europe

In Europe, glucosamine is approved as a medical drug and is sold in the form of glucosamine sulphate. In this case, evidence of safety and efficacy is required for the medical use of glucosamine and several guidelines have recommended its use as an effective and safe therapy for osteoarthritis. The Task Force of the European League Against Rheumatism (EULAR) committee has granted glucosamine sulphate a level of toxicity of 5 in a 0-100 scale, and recent OARSI (OsteoArthritis Research Society International) guidelines for hip and knee osteoarthritis also confirm its excellent safety profile.

Bioavailability and pharmacokinetics

Two recent studies confirm that glucosamine is bioavailable both systemically and at the site of action (the joint) after oral administration of crystalline glucosamine sulfate in osteoarthritis patients. Steady state glucosamine concentrations in plasma and synovial fluid were correlated and in line with those effective in selected in vitro studies.

The bioavailability of glucosamine sulfate is around 20%.

Natural sources

Glucosamine is naturally present in the shells of shellfish, animal bones and bone marrow. It is also present in some fungi, such as Aspergillus niger.

Pharmacodynamics

The possible effects of glucosamine sulfate in patients with osteoarthritis may be the result of its anti-inflammatory activity, the stimulation of the synthesis of proteoglycans, and the decrease in catabolic activity of chondrocytes inhibiting the synthesis of proteolytic enzymes and other substances that contribute to damage cartilage matrix and cause death of articular chondrocytes.

Glucosamine is an essential substrate in the natural formation of the GAG matrix.

Glucosamine is thought to stimulate synovial production of hyaluronic acid and is also claimed to inhibit cartilage degrading liposomal enzymes.

Clinical studies

There have been multiple clinical trials of glucosamine as a medical therapy for osteoarthritis, but results have been conflicting. The evidence both for and against glucosamine’s efficacy has led to debate among physicians about whether to recommend glucosamine treatment to their patients.

Multiple clinical trials in the 1980s and 1990s, all sponsored by the European patent-holder, Rottapharm, demonstrated a benefit for glucosamine. However, these studies were of poor quality due to shortcomings in their methods, including small size, short duration, poor analysis of drop-outs, and unclear procedures for blinding. Rottapharm then sponsored two large (at least 100 patients per group), three-year-long, placebo-controlled clinical trials of the Rottapharm brand of glucosamine sulfate. These studies both demonstrated a clear benefit for glucosamine treatment. There was not only an improvement in symptoms but also an improvement in joint space