What is glucosamine?

(Extraído de medicalnewstoday.com)

Glucosamine is a naturally occurring substance found in the fluid around our joints. It is naturally present in animal bones, bone marrow, shellfish and fungi. Glucosamine plays a vital role in building cartilage and is commonly consumed as a supplement by people with arthritis, especially osteoarthritis.

Glucosamine, especially glucosamine sulfate, is harvested from the shells of shellfish and put into dietary supplements. It can also be made in the laboratory.

Glucosamine can come in different forms, including:

• glucosamine sulfate
• glucosamine hydrochloride
• N-acetyl-glucosamine

Although similar, the three forms may not have the same effect when used as dietary supplements.

Most studies that have examined the potential health benefits of glucosamine have focused on glucosamine sulfate.

Glucosamine-containing dietary supplements often have other ingredients added in, including chondroitin sulfate, MSM or shark cartilage. Although some people say the combinations help, there is no scientific proof that they do, says the National Institutes of Health.

The National Institutes of Health (NIH) adds that skin creams containing glucosamine for arthritis pain probably provide relief because of other substances in them, and not the glucosamine. "There is no evidence that glucosamine can be absorbed through the skin."

The NIH also commented that some glucosamine sulfate products do not contain what their labeling states - tests showed from 0% to 100% glucosamine content. In other tests, when the label claimed the product had glucosamine hydrochloride, it was glucosamine sulfate.

 

Why do we need glucosamine?

Glucosamine is vital for building cartilage. Cartilage is a flexible, tough connective tissue found in several areas of the body. This fine, rubbery tissue functions as padding, a cushion for bones and joints.

Joint cartilage requires glucosamine because it is a precursor for glycosaminoglycans (glucosamine makes glycosaminoglycans). Glycosaminoglycans are a major component of joint cartilage.

Sulfur needs to be incorporated into cartilage in order to make and repair it. Glucosamine plays a crucial role in incorporating sulfur into cartilage.

As we age, glucosamine levels go down, which can lead to eventual joint deterioration.

 

Why do people take glucosamine supplements?

According to the National Center for Complementary and Alternative Therapy, a 2007 National Health Interview survey found that 17.7% of adults in the USA regularly took some type of dietary supplement. Of those people, 19.9% took glucosamine, the second most popular dietary supplement after fish oil/omega 3/DHA (37.4%).

Glucosamine supplements are most commonly taken by people suffering from osteoarthritis, inflammatory bowel disease (IBD) and ulcerative colitis.

Osteoarthritis

Several scientific studies have shown that glucosamine supplements may help patients with osteoarthritis (OA), especially OA of the hip or knee.

The studies found that glucosamine probably:

• Reduced osteoarthritis-related pain
• Improved function in patients with knee or hip osteoarthritis
• Reduced stiffness
• Reduced swelling in the joints
• Continued to provide relief of symptoms up to 3 months after patients stopped treatment

However, the Glucosamine/chondroitin Arthritis Intervention Trial (GAIT), which was performed at 16 sites across the United State and published in NEJM (New England Journal of Medicine found that glucosamine plus chondroitin sulfate did not provide significant relief from osteoarthritis among all 1,600 participants.

In a smaller subgroup of the study, however, patients with moderate-to-severe pain reported significant relief from the glucosamine/chondroitin combination.

In 2008, researchers reported on a 2-year ancillary study at nine sites in the USA with a subset of participants from the original trial. The results, published in Arthritis & Rheumatism showed that glucosamine and chondroitin sulfate, together or alone, fared no better than placebo in slowing loss of cartilage in knee osteoarthritis. However, the patients on placebo had a smaller loss of cartilage or joint space width than predicted.

Most studies appear to indicate that if you have osteoarthritis and your symptoms of pain are moderate-to-severe, glucosamine or a glucosamine/chondroitin combination may help, otherwise it is probably no better than placebo.

Inflammatory bowel disease (IBD) and ulcerative colitis

IBD involves long-term inflammation of part or all of the digestive tract. Examples of IBD include Crohn's disease and ulcerative colitis. IBD is painful and can be debilitating and sometimes life-threating if there are complications.

Ulcerative colitis affects part of the digestive tract while Crohn's disease can cause inflammation in any part of the lining along the digestive tract, and frequently spreads deep into affected tissue.

Researchers in a pilot study carried out at the University Department of Paediatric Gastroenterology, Royal Free, London, UK, concluded that N-acetyl glucosamine (GlcNAc), a glucosamine-like dietary supplement, showed promise as a cheap and non-toxic treatment in chronic inflammatory bowel disease for children who did not respond well to other treatments (severe treatment-resistant inflammatory bowel disease). Ten had Crohn's disease and two ulcerative colitis.

As it was a small study the investigators wrote in the journal Alimentary Pharmacology & Therapeutics (December 2000 issue) "It may have the potential to be helpful in stricturing disease. However, controlled trials and an assessment of enteric-release preparations are required to confirm its efficacy and establish indications for use."

Researchers from Juntendo University, School of Medicine, Tokyo, carried out experiments on IBD induced laboratory rats. They reported in the International Journal of Molecular Medicine that "....glucosamine could prove to be a useful agent for IBD."

Multiple sclerosis

Scientists at the University of California, Irvine, found that N-acetyl glucosamine (GlcNAc) supplements suppressed the damaging autoimmune response that occurs in MS (multiple sclerosis).

Dr. Michael Demetriou, Ani Grigorian and colleagues explained in The Journal of Biological Chemistry that GlcNAc inhibited the growth and function of abnormal T-cells that mistakenly make the MS patient's immune system attack and destroy central nervous system tissue that insulates nerves (myelin).

Dr. Demetriou said "This sugar-based supplement corrects a genetic defect that induces cells to attack the body in MS, making metabolic therapy a rational approach that differs significantly from currently available treatments."

In their experiment they used laboratory mice with MS-like autoimmune disease. The scientists found that when the mice with leg weaknesses were give GlcNAc orally, the supplement suppressed T-cell hyperactivity and autoimmune response by raising sugar modifications to the T-cell proteins, resulting in a reversal of the progression to paralysis.

A research team from the Jefferson Medical College found that OTC (over-the-counter) glucosamine helped delay the onset of MS symptoms in an animal experiment. They found it also improved the mice's ability to move and walk.

Glucosamine is used for many other conditions and illnesses. However, most studies have found they are either ineffective, no conclusion can be reached, while some warn of potential harms (as in "allergies" below). From the list below, the only one with a positive study is glucosamine use for temporomandibular joint problems:

• Sports injuries - according to a study published in the Journal of Athletic Training, "no evidence to date supports or refutes a carryover effect to the athletic population and the injuries that occur in sport".
• Chronic low back pain - a study published in the BMJ (British Medical Journal) concluded that the benefits of glucosamine for lower back pain could "neither be demonstrated nor excluded based on insufficient data and the low quality of existing studies".
• Temporomandibular joint (TMJ) problems - the Journal of Rheumatology published a study which concluded "Glucosamine (GS) and ibuprofen reduce pain levels in patients with TMJ degenerative joint disease. In the subgroup that met the initial efficacy criteria, GS had a significantly greater influence in reducing pain produced during function and effect of pain with daily activities. GS has a carryover effect".
• Venous insufficiency - there are no scientific studies to either recommend or discount glucosamine for venous insufficiency.
• Allergies - although many people anecdotally swear by glucosamine for a number of allergies, studies warn about a possible allergic reaction for some people, especially those allergic to shellfish. The Mayo Clinic warns that since glucosamine is commonly made from the shells of shellfish, individuals with shellfish allergies or iodine hypersensitivity are likely to have an allergic reaction to products containing glucosamine.
• Asthma - in fact, the journal American Family Physician warns that glucosamine should be used with caution in patients with asthma.

Glucosamine safety concerns

According to the National Institutes of Health, glucosamine is LIKELY SAFE when used properly by adults.

The NIH adds that some mild side effects have occasionally (rarely) been associated with glucosamine intake, including:

• drowsiness
• skin reactions
• headache

Pregnancy and breastfeeding - nobody knows whether glucosamine is safe for pregnant or breastfeeding mothers. Until scientific studies can conclude one way or another, the NIH recommends women do not take glucosamine while breastfeeding or during pregnancy.

Asthma - several medical journals warn that glucosamine may cause an asthma attack in some people. One report linked asthma to glucosamine intake, according to the NIH, but the researchers could not determine compellingly whether glucosamine was the culprit.

Diabetes - some earlier studies had suggested that glucosamine might raise blood glucose levels in patients with diabetes. Later studies suggested the opposite. It appears that glucosamine probably does not affect blood glucose levels in patients with type 2 diabetes.

Shellfish allergy - some glucosamine products are made from the shells of shellfish. People with shellfish allergies should be aware of this and consider asking their pharmacist for man-made glucosamine supplements. However, the NIH adds that US health authorities have received no reports of allergic reactions to glucosamine among people with shellfish allergies.

Written by Christian Nordqvist