Glucosamine is a natural compound found in the human body; more specifically, it is an amino monosaccharide (a nitrogen-containing sugar) that is thought to play a role in cartilage formation and repair and may also have anti-inflammatory capabilities. It is sold as a nutritional or dietary supplement in three forms: glucosamine hydrochloride (glucosamine HCl), glucosamine sulfate, and N-acetyl-glucosamine (NAG). Most of the medical research has been done on the first two forms, particularly glucosamine sulfate.
When taken as an oral supplement, glucosamine is sometimes used in the treatment of osteoarthritis. Osteoarthritis is the most common type of arthritis. According to the U.S. Centers for Disease Control and Prevention (CDC), more than 30 million people in the United States suffer from osteoarthritis. Also called degenerative joint disease, osteoarthritis is caused by deterioration or loss of cartilage in one or more joints of the body. The symptoms of the condition range from mild pain and stiffness to complete loss of use of the joint, and it may or may not have an identifiable cause; people aged 60 years or older often develop osteoarthritis.
Unlike the less common rheumatoid arthritis, osteoarthritis is not marked by inflammation. Whereas osteoarthritis is commonly associated with being overweight, cartilage deterioration can be caused by excessive wear and tear on the joints, which may be due to excessive physical exercise or exertion. Many athletes take glucosamine supplements to help prevent cartilage damage.
The use of glucosamine in osteoarthritis therapy is considered generally safe among medical professionals; however, it is not completely accepted within the medical community as being effective for osteoarthritis treatment and is considered an alternative medicine. In the United States, the Food and Drug Administration (FDA) has not approved the use of glucosamine for medical use in humans. It is classified as a dietary supplement, so FDA approval is not needed as long as companies do not advertise it as a treatment for a medical condition. In Europe, however, glucosamine sulfate is approved as a medical drug.
Besides osteoarthritis, glucosamine is also used to relieve symptoms of leg pain, rheumatoid arthritis, chronic venous insufficiency, diabetes and related conditions, inflammatory bowel disease (such as ulcerative colitis and Crohn's disease), and temporomandibular joint (TMJ) disorders. Scientific results show some positive evidence for the effective use of glucosamine for osteoarthritis; however, scientific evidence is much more unclear regarding the other diseases.
Glucosamine is also known as 2-amino-2-deoxyglucose, 2-amino-2-deoxy-beta-D-glucopyranose, and chitosamine. The chemical symbol for glucosamine is C6H13NO5. Glucosamine is taken from the shells of crabs, lobsters, and shrimp. Within these shellfish, glucosamine is made naturally in the form of glucosamine-6-phosphate, which eventually makes glycosaminoglycans, among other substances. Since glucosamine-6-phosphate helps to regulate the production of joint cartilage and glycosaminoglycans are a major component of cartilage, glucosamine may help to rebuild cartilage and treat arthritis. Whether these glucosamine processes could be involved in human arthritis remains undecided in the medical community. Not all medical professionals believe glucosamine is effective.
The two most commonly sold forms of glucosamine are glucosamine sulfate and glucosamine hydrochloride. Glucosamine is often sold in combination with other supplements, such as chondroitin sulfate (a sulfated glycosaminoglycan composed of a chain of alternating sugars) and methylsulfonylmethane (MSM, an organic sulfur compound within the chemical class of sulfones). Glucosamine is found in various forms when sold commercially, including capsules (500 mg, 550 mg, 750 mg, and 1,000 mg), liquid (500 mg per five mL), tablets (340 mg, 500 mg, and 1,000 mg), and powder.
When glucosamine is taken orally into the body (as a pill), according to conclusions from scientifically based animal studies, it is absorbed into the small intestine. It then travels into the liver where most of it is metabolized. Based on these studies, some of it does apparently go to the cartilage; however, it is not known how much is actually transmitted to the joints. It is primarily removed from the body through urine.
In 2002, the National Institutes of Health sponsored a large, multi-institutional clinical trial to test the effects of chondroitin sulfate, glucosamine, and the combination of the two on knee osteoarthritis. (Chondroitin is a carbohydrate that is a component of cartilage. It is thought to help promote water retention and elasticity in cartilage and help prevent enzymes from destroying cartilage.) The study was one of the largest of its kind at that time with respect to research into the two substances.
The study found that patients taking glucosamine, chondroitin sulfate, or a combination of the two had no significant decrease in mild osteoarthritis symptoms when compared to taking a placebo. Patients who took celecoxib had the most significant decrease in the severity of their symptoms. However, glucosamine and chondroitin sulfate together did seem to help people with moderate-to-severe pain, as compared to a placebo.
Since then, other studies have been conducted on the efficacy of glucosamine, chondroitin, and their combination, including two follow-up GAIT studies. The first, concluded in 2008, had participants in the original GAIT study continue taking supplements for a total of two years. The goal was to assess the progression of cartilage deterioration. Although those taking only glucosamine showed the least amount of cartilage loss after two years, the researchers noted no significant differences between taking glucosamine supplements, prescription medications, or a placebo.
Another study, published in the September 2010 issue of the British Journal of Medicine, analyzed ten published trials to determine if glucosamine, chondroitin, or a combination of the two, helped to relieve pain. A total of 3,803 patients, with painful symptoms from hip or knee osteoarthritis, had participated in the studies. Dr. Peter Jüni and his colleagues at the University of Bern (Switzerland) found glucosamine, chondroitin, and their combination did not reduce joint pain or slow cartilage loss when compared to placebo.
Subsequently, the reliability of the data from the Jüni-led meta-analysis study was questioned. Glucosamine is one of the most common nonmineral, non-vitamin dietary supplements used by adults. However, precaution should be used when taking it, because its level of effectiveness and safeness are not completely understood. Still, several medical organizations recommend glucosamine. For instance, the OsteoArthritis Research Society International (OARSI) states that “glucosamine and chondroitin sulphate may be effective in providing symptomatic pain relief in patients with knee osteoarthritis.”
In a 2015 review of the literature published through 2013, the authors found that chondroitin, alone or combined with glucosamine, was better than a placebo at improving osteoarthritis pain, and that the benefit was small to moderate. The authors observed, however, that most of the studies they surveyed were of low quality.
A 2018 survey of studies on the use of glucosamine for TMJ osteoarthritis found that glucosamine was as effective as ibuprofen in the short term, but was not better than a placebo over six weeks.
No official recommended dosage for glucosamine has been established. Typical doses for adults range from 500 to 2,000 milligrams (0.5 grams) daily, either taken once or divided through the day. As of 2018, very little research had been done on the use of glucosamine in children, and there was no recommended dosage for people under the age of 18.
The amount of glucosamine varies with the supplemental form. Pure glucosamine hydrochloride is at a concentration of about 83% in the glucosamine base; pure glucosamine sulfate is approximately 65%, and pure N-acetyl glucosamine is around 75%.
High doses of glucosamine have been known to cause gastric upsets and diarrhea.
If choosing to take glucosamine, consumers should take it for at least six to eight weeks. It generally takes this amount of time before any noticeable effects are felt. If a reduction of symptoms is not noticed at the end of this period of time, the Arthritis Foundation states that glucosamine will probably not help.
The Arthritis Foundation recommends that consumers using glucosamine buy from established companies, because they can more easily be held accountable for their products. The foundation also advises consumers to read product labels carefully, ask the pharmacist questions when necessary, and consult with their doctors before taking glucosamine. Without consent from the prescribing physician, glucosamine should not be used as a replacement for any prescription medicines already being taken.
Because glucosamine is not approved by the FDA, a product's safety and formulation is determined solely by the manufacturer. Quality and content may vary among manufacturers. Tests have been performed by ConsumerLab.com
Medical research has not been comprehensive enough to determine whether it is safe for pregnant or breastfeeding women to take glucosamine. Until more is known in the scientific community, most medical professionals do not recommend taking glucosamine during pregnancy or while breastfeeding.
The use of alcohol, tranquilizers, sedatives, anticonvulsant drugs, antianxiety drugs, muscle relaxants, and/or antihistamine medicines may intensify the side effect of drowsiness sometimes felt with glucosamine, adversely affecting the user's concentration.
Because glucosamine is derived from the shellfish, people with shellfish allergies or iodine hypersensitivity may not want to take glucosamine. According to the U.S. National Institutes of Health (NIH), throat swelling may occur if people with shellfish allergies react negatively to glucosamine. It is important to note that people with shellfish allergies are usually allergic to the skin (protein) of shellfish, and not to the actual shells (chitin). According to a 2004 article from the Journal of Allergy and Clinical Immunology, most people with shellfish allergies can safely take glucosamine. As of 2018, no research reported any risk, but it is wise to ask a physician before taking any new medicines.
Glucosamine taken above recommended dosages could decrease the effectiveness of insulin or other drugs that control blood sugar levels in diabetes. According to the NIH, some studies show a connection, whereas other studies do not; it is, however, considered a possible risk by the medical community.
Clinical studies have consistently shown that glucosamine is safe when used as directed. According to the NIH, possible side effects may include drowsiness, headache, upset stomach, insomnia, skin reactions, light sensitivity, and nail toughening. Rare symptoms include abdominal pain, appetite loss, vomiting, nausea, intestinal gas, heartburn, and diarrhea.
People who are overweight or have diabetes or liver disease should check their blood sugar levels more frequently when taking glucosamine because it is an amino sugar.
Reports from the NIH suggest that glucosamine may also increase the risk of bleeding, especially when taking aspirin, blood thinners, anti-platelet drugs, and nonsteroidal anti-inflammatory drugs. If taking blood-thinning medication or daily aspirin therapy, blood-clotting time should be tested frequently.
People with asthma should be cautious about taking glucosamine. The use of glucosamine has been possibly linked to an increase in the frequency and severity of asthma attacks, although no concrete studies have shown that glucosamine could cause an asthma episode. Patients should always consult with their doctor before taking any new drugs or supplements, including glucosamine.
See also Arthritis diet ; Crohn's disease .
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William Arthur Atkins
Revised by Amy Hackney Blackwell, PhD