One has to consider a number of issues with these supplements:




Product quality is a serious problem with these supplements. One independent product testing company,, found that several combination products of glucosamine and chondroitin were low in chondroitin sulphate (the more expensive ingredient) including one product that only had 90mg when it should have been 500mg! A study published in the Journal of Rheumatology in 2002 analysed 14 commercially available glucosamine sulphate products and found that the amount of glucosamine varied from 59% to 138% of the label amount and a Consumer Report in 2002 found a considerable variation in glucosamine and chondroitin sulphate content for a number of products.


So there is a big problem relating results of studies such as GAIT - that have used standardised, regulated glucosamine and chondroitin sulphate preparations - to anyone considering using over-the-counter glucosamine and chondroitin sulphate products that are classed as dietary supplements. In the published results of GAIT the investigators actually state that products identical to the ones used in GAIT may not be commercially available. If you can't buy the products used in the study how relevant are the results of GAIT to the person on the street with knee pain from osteoarthritis?

What type, how much and when?

Glucosamine is available in several different chemical formats. The GUIDE study, in line with several previous studies, used glucosamine sulphate whereas the GAIT study used glucosamine hydrochloride (HCL). Does this make a difference? Well there is considerable disagreement as to whether one form of glucosamine works better than the other. Glucosamine sulphate is made by chemically modifying glucosamine HCL. Some experts say they perform equally well whereas other experts based on animal studies suggest that glucosamine HCL is an 'inactive' form and that glucosamine sulphate works better.

In the GAIT study the supplements were taken three times a day whereas in GUIDE they were taken just once a day. There are suggestions that once a day gives better dosing but this hasn't been backed up scientifically to date.

Assuming you find a reliable manufacturer, what is the best way to get the glucosamine and chondroitin sulphate to your knee cartilage? Glucosamine and chondroitin sulphate supplements come in a variety of pills, capsules, powders and liquid formats. Some people find the large tablets difficult to swallow and prefer to take the supplements in a beverage form. There are an increasing number of commercial companies 'jumping on the joint health bandwagon' and marketing 'super joint care' drinks. Some medics are recommending glucosamine in a liquid format on the basis that significantly more of the glucosamine actually gets into the blood stream compared with pills. In addition some medics are not recommending glucosamine and chondroitin sulphate combinations to patients as the chondroitin sulphate is so poorly absorbed into the blood stream.

In both the GAIT and GUIDE studies 1500mg of glucosamine daily was used and in the GAIT study 1200mg of chondroitin daily was used. However, some manufacturers suggest that glucosamine and chondroitin sulphate supplements should be taken in two phases, for example -

  • A loading phase of a month of increased levels of glucosamine (up to 2250mg) and 1200mg of chondroitin sulphate.
  • A maintenance phase of 1500mg of glucosamine and 800mg of chondroitin sulphate.

Other suggestions are that glucosamine and chondroitin sulphate doses should be calculated based on a person's body weight. One recommendation is 20mg of glucosamine for every 1kg of body weight, whilst another suggestion is as follows -

  • If body weight is less than 54.5kg take 1,000mg glucosamine and 800mg chondroitin sulphate.
  • If body weight is between 54.5 and 91kg take 1,500mg glucosamine and 1,200 mg chondroitin sulphate.
  • If body weight is more than 91kg take 2,000mg glucosamine and 1,600mg chondroitin sulphate.

Are these ploys by supplement companies to sell more of their product or is there a scientific basis for these recommendations? Well, at present the evidence for doses and schedules is fairly sparse and that is one of the reasons why daily doses of 1500mg of glucosamine and 1200mg of chondroitin sulphate are common recommendations.

What about the source of these products?

Chondroitin sulphate is usually produced from cow (bovine) cartilage but can be produced from pig (porcine), chicken and even shark cartilage. Glucosamine on the other hand is derived from shellfish, usually shrimp, lobster or crab shells. There are forms that are available for vegetarians, Kosher diets and those people with shellfish allergies as chondroitin sulphate can be produced from algae or fungus and glucosamine can be produced from corn, but these products tend to be considerably more expensive than their animal counterparts. Also bear in mind that if you are taking supplements in capsule form the capsule itself is often made from bovine gelatin so check the ingredients of the capsule as well as the contents.

One of the concerns that has been raised over the ingestion of bovine chondroitin sulphate is the risk of acquiring Bovine Spongiform Encephalitis (BSE) commonly known as 'Mad Cow Disease'. BSE is associated with neural tissue and the fact that the cartilage that is used to produce chondroitin sulphate is generally taken from the cow's windpipe (trachea) and has very limited neural tissue (spinal cord, brain, nerve) would tend to indicate a very low risk of acquiring BSE from chondroitin sulphate supplements. However, the way that the chondroitin sulphate is extracted and processed doesn't guarantee the destruction of BSE if any is present. So although there are no known direct links of BSE to chondroitin sulphate supplementation if you are concerned about the risk you should look for non-bovine sources of chondroitin sulphate. Similarly, although as far as the author is aware there have been no known cases of anyone contracting Asian bird flu from glucosamine supplements, if this concerns you then look for a non-chicken source of glucosamine.


Other factors

Body Mass Index

Body mass index (BMI) is a ratio of a person's weight to height that has been recognised by the US National Institutes of Health (NIH) and The World Health Organisation as a measure of obesity. According to current health guidelines you are classed as overweight if you have a BMI of 25-29.9 and obese if you have a BMI of 30 or greater.

In the GAIT study the average BMI for the participants in the study was 31.7 and this group can therefore be given an overall classification of 'obese'. This has implications for joint pain, especially in the knee, as it is directly linked to body weight as increased weight puts increased load on the joint.

A study published in the journal Osteoarthritis and Cartilage in 2005 found that for a group of patients with knee OA and an average BMI of 35.9 a weight reduction of 10% improved patient function by 28%.

Click here to calculate your own BMI


Chondroitin sulphate production in the body can be hindered if there is a deficiency of some key vitamins and minerals, in particular manganese, vitamin C and vitamin A. As participants in the GAIT study didn't appear to undergo a dietary analysis prior to the start of the trial it is possible that some individuals may have had deficiencies in these key substances.

There was also another notable omission in the GAIT study design in that participants, according to the published report in NEJM, weren't asked if they were currently taking or had been recently taking glucosamine or chondroitin sulphate before they started the trial. It is known that glucosamine and chondroitin supplementation takes 6 to 12 weeks to reach peak effect and therefore a long wash out period is needed to avoid a carry over effect of prior use. With such widespread use of these supplements nowadays it is not unreasonable to suggest that a number of the participants were either taking or had recently taken glucosamine and/or chondroitin supplements.


Are there any risks?

The good news is that side effects of taking glucosamine and chondroitin sulphate tend to be mild and not very common. In the GAIT study a number of patients did experience mild side effects such as upset stomachs and nausea but the incidence was at the same level for all the groups including the patients who took the fake pills. There are no long-term studies looking at adverse effects of on-going glucosamine and chondroitin supplementation and there have been no reported incidences of overdose.

There has been some suggestion that glucosamine may worsen insulin resistance and although this hasn’t been proven as yet the general advice is for diabetics to carefully monitor their blood sugar levels when using glucosamine supplementation and not to start taking these supplements without consulting their doctor. Chondroitin has a similar format to blood-thinning drugs so anyone taking such medications, e.g. warfarin, should seek medical advice before taking these supplements.

Medical associations recommend that anyone who is taking any medications, has a health condition, is pregnant or is a child should speak to their doctor before starting to use glucosamine and chondroitin supplements.


What does this mean for YOU?

Glucosamine and chondroitin are extremely popular supplements that have received considerable press coverage over the last few years and there are lots of anecdotal comments flying around. Some people will swear by glucosamine and chondroitin sulphate and others have found it didn't help their knee pain and will tell you it was a waste of money. So what do the latest study results mean for you?

Well, the best that can be said at present, off the back of the results of the GAIT study, is that glucosamine and chondroitin supplementation may provide some pain relief for knee osteoarthritis sufferers especially those people with moderate to severe pain. At what cost does this pain relief come? Well, even though the side effects are relatively minor these supplements don't work for everyone and they can be expensive ($1-2 per day). If you start to take glucosamine and chondroitin sulphate and are not finding any effect on your pain after 3 months the advice at present is to stop taking them. So on one hand the risks of side effects are low but on the other hand it is difficult to assure the quality of the products as they are not produced to pharmaceutical grade in the US and UK. So if you are looking at it from a risk to benefits point of view any risk is more likely more to your wallet than to your health.

Putting things into perspective - supplements are just that. They are meant to supplement NOT replace your usual knee management strategies. Yes they may give you some additional pain relief, which is fantastic, but there are currently no studies that provide evidence that glucosamine and chondroitin sulphate actually slow down the progression of the osteoarthritis. There are other management strategies that you can adopt that are likely to offer an equal, if not greater level, of pain relief than glucosamine and chondroitin supplementation. That isn't to say that you shouldn't consider supplementation but you should view supplementation as part of your overall management plan not THE management plan.

Editor's note 17th September 2010

There has been a new review published in the British Medical Journal - see Effects of glucosamine, chondroitin, or placebo in patients with osteoarthritis of hip or knee: network meta-analysis. and which concluded that "Chondroitin, glucosamine, and their combination do not have a clinically relevant effect on perceived joint pain or on joint space narrowing" and "Estimated differences between supplements and placebo were less pronounced on average in industry independent trials, and estimated treatment effects in industry independent trials were small or absent and clinically irrelevant."

Main References

Christensen, R., Astrup,A. & Bliddal, H. (2005). Weight loss: the treatment of choice for knee osteoarthritis? A randomized trial. Osteoarthritis Cartilage. 13(1):20-7

Cibere, J. et al. (2004). Randomized, double-blind, placebo-controlled glucosamine discontinuation trial in knee osteoarthritis. Arth. & Rheum. 51(5):738-745

Clegg, D.O. et al. (2006). Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. New Eng. J. Med. 354(8):795-808

Barnhill, J.G. et al. (2006). Chondroitin product selection for the glucosamine/chondroitin arthritis intervention trial. J. Am. Pharm. Assoc. (Wash DC). 46(1):14-24

Herrero-Beaumont, G. et al. (2005). Effects of Glucosamine Sulfate on 6-Month Control of Knee Osteoarthritis Symptoms vs Placebo and Acetaminophen: Results from the Glucosamine Unum in Die Efficacy (GUIDE) Trial. Paper presented at American College of Rheumatology Annual Scientific Meeting, San Diego, USA

Hungerford, D.S. & Jones, L.C. (2003). Glucosamine and chondroitin sulfate are effective in the management of osteoarthritis. J. Arthroplasty. 18(3 Suppl 1):5-9

Mehrotra, C. et al. (2004). Arthritis, body mass index, and professional advice to lose weight: implications for clinical medicine and public health. Am. J. Prev. Med. 27(1):16-21

Russell, A.S., Aghazadeh-Habashi, A. & Jamali, F. (2002). Active ingredient consistency of commercially available glucosamine sulfate products. J. Rheum. 29:2407-2409

Persiani, S. (2005). Glucosamine oral bioavailability and plasma pharmacokinetics after increasing doses of crystalline glucosamine sulfate in man. Osteoarthritis Cartilage. 13(12):1041-9

Towheed T.E. et al. (2005). Glucosamine therapy for treating osteoarthritis. The Cochrane Database of Systematic Reviews Issue 2. Art. No.: CD002946.pub2. DOI: 10.1002/14651858.CD002946.pub2.

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