Glucosamine - good for the joints?

Glucosamine is one of the most popular supplements, and has been growing in popularity in the UK recently. It is primarily used to improve symptoms of joint pain and stiffness, and is often used by those with osteoarthritis. Many other people take it when single joints become affected by injury.

What is glucosamine?

Glucosamine is an amino sugar, which as its name suggests, is a combination of glucose - a sugar, and amine - a molecule of nitrogen with hydrogen, NH2. It is produced in the body by combining glucose (blood sugar) and the amino acid, glutamine. These two nutrients are common in our diet, so it is only if our ability to join them together diminishes, that we will become deficient in glucosamine. The enzyme, glucosamine synthetase is responsible for synthesizing glucosamine from glucose and glutamine, and it is thought, that this enzyme has reduced power in the elderly1

After being synthesized from glucose and glutamine, or absorbed from the intestines, glucosamine goes on to become part of large glycans molecules that make up cartilage, joint lubricating fluids and other connective tissues throughout the body. The million dollar question is: Do some people need oral glucosamine in addition to the glucose and glutamine that they already consume as part of their normal diet?

Glucosamine can only reach damaged cartilage by diffusing through the extracellular matrix from blood vessels that are distant from the cartilage. This is because cartilage has no direct supply of blood. One reason that a person may need additional glucosamine could be that they don't naturally produce enough. Inflammation or injury could affect a joint, without the body producing enough glucosamine to make a decent job of repairing damaged cartilage. In this case supplemental glucosamine may make a difference by allowing more glucosamine to diffuse from the blood to the damaged cartilage.

Can supplemental glucosamine help the joints?

A large number of studies have been carried out with conflicting results. Some seem to show a clear benefit, while others have shown no benefit. To this should be added the clinical experience of many health professionals, who note that many of their clients find glucosamine effective at both reducing pain, and increasing functionality in damaged joints.

Positive studies.

Glucosamine was found to reduce the need for surgery after long term supplementation in people with osteo-arthritis2. This Belgium study appeared to show that there was less need for medication for osteoarthritic symptoms following glucosamine supplementation as well. In another Canadian study glucosamine was shown to normalise the activity of damaged joints in a experiment on rabbits3. This study produced evidence that glucosamine supplementation could counter the effects of early stage osteoarthritis, by normalising the amount of bone mineralisation. A 2001 study, this time on humans, showed that the structure of the joint improved or at least did not deteriorate when comparing people taking glucosamine sulphate with those on a placebo pill4. The space between knee bones was virtually maintained in those on glucosamine sulphate for 3 years, wheres those on a placebo treatment saw the space between bones diminsh by 1/3rd of a millimetre. Such results suggest that glucosamine has a real effect on the long term health of the joints in our body.

Negative studies.

There are studies that show fewer positive effects for glucosamine and a recent pooling of results from 12 selected trials in 2010 concluded that glucosamine had no positive effect. This same study cautioned that many of the positive trials were sponsored by the same supplement company, Rottepharm5.

Which type of glucosamine supplement is best?

There are three main types of glucosamine supplement.

Glucosamine sulphate.

This is the type most commonly used in trials and recomended by health authorities. However, some claim that there really is not much difference between glucosamine sulphate and glucosamine hydrochloride as the glucosamine splits away from the sulphate or hydrochoride in the acidic environment of the stomach. It has been reported to cause gastro-intestinal disturbance more often that glucosamine hydrochloride1.

Glucosamine hydrochloride.

This is the cheapest version and probably as effective as any of the others. In some people glucosamine hydrochloride may be a better bet than glucosamine sulphate. The rationale for this is that some people have more sulphate reducing bacteria in their gut than others. These bacteria produce hydrogen sulphide which is linked with cancer of the colon and ulcerative colitis1.

N-acetyl glucosamine.

This has been used to reduce symptoms of Multiple sclerosis and type 1 diabetes as well as in the treatment of osteoporosis6. N-acetyl glucosamine is basically glucosamine that has had another molecule added to it. This normally happens in the body, and is part of the process of producing the large glycans molecules that help provide the framework for our joints and the lubricating fluids which surround them. As with glucosamine, there is a possibility that the synthesis of n-acetyl glucosamine is not effective and that by supplementing n-acetyl glucosamine you bypass this inefficiency. However, n-acetyl glucosamine is the most expensive form to supplement.

In practice glucosamine is often combined with other joint supplements such as chondroitin and methyl-sulfonyl-methane (MSM). These are added to further benefit joint health. Like glucosamine these supplements are generally safe to use and may have a positive effect.


Chondroitin is a glucosaminoglycan (GAG), and is made up of repeating untis of two sugar like molecules, N-acetylgalactosamine and glucuronic acid. It is the main gel like component in joints, helping them recover their shape after compression. Like glucosamine, chondroitin can be produced in the body from blood sugar and amino acids in our diet. In theory glucosamine itself, could help form chondroitin in the body by converting to galactosamine and then being acetylated to N-acetylgalactosamine.


MSM is a source of both sulphur and methyl groups, both of which could be anti-inflammatory and helpful in conditions such as osteoarthritis. There are not many studies on MSM, but it is often combined with glucosamine and chondroitin.

For vegetarians and those allergic to shellfish vegetarian glucosamine is available in the UK from a number of outlets one of which I've listed under references at the end7.

How much should I supplement?

If you are going to supplement glucosamine it is normally taken as 3 lots of 500mg per day for an adult. It can interact with the following medications:

  • The blood thinning effect of Warfarin may be increased, so it is important to consult your doctor before combining these two.
  • Diabetes drugs such as insulin or other blood sugar lowering drugs may need their dosage to be changed if you take glucosamine.It is thought that glucosamine could raise blood sugar levels, although evidence for this is not conclusive. It is wise to monitor blood sugar levels after taking glucosamine, if you are diabetic.
  • Chemotherapy drugs such as Doxorubicin, Etoposide and Teniposide, which are designed to slow the rate at which cancers develop may interact badly with glucosamine. It is thought possible that glucosamine may have the opposite effect, although there is not a great deal of evidence for this.

DrDobbin says:

Many people experience improvement in symptoms while taking glucosamine. If the body is not making enough it is likely that supplemental glucosamine could help. It is certainly worth a try if you have a persistant problem with one or more of your joints. Give it 3 months to see if you notice an improvement. If symptoms improve it is probably worth continuing with the supplement.

It is worth bearing in mind that vitamin K should also help. It is available from green leafy vegetables such as broccoli, cabbage and spinach. It has been found that those low in vitamin K are more prone to osteoarthritis8.


1) Health Defence, Dr Paul Clayton, ISBN 0-905553-63-2