Arthritis / Glucosamine and chondroitin: dose, efficacy and contraindications

By Cristiano Antonino On Jun 7, 2023

Glucosamine (also glucosamine) is an aminopolysaccharide involved in the synthesis of glycosylated proteins and lipids

It was first identified in 1876 by a German surgeon, Georg Ledderhose, but it took until 1939 for its stereochemistry to be fully understood thanks to the work of Walter Norman Haworth, a British chemist.

Glucosamine is a substance abundantly present in the shells of crustaceans and it is from these shells that it is commercially produced by hydrolysis.

Glucosamine is involved in the production of glycosaminoglycans, which are essential for cartilage.

Like many other substances, with aging, the amount of glucosamine produced by the body decreases and obviously the cartilage degrades.

Research has shown that supplementing with glucosamine is able to block osteoarthritis in 85% of cases.

No major side effects were recorded from oral administration of glucosamine.

Types of glucosamine

There are various forms of glucosamine; among the best known we can mention glucosamine sulphate, glucosamine hydrochloride and n-acetylglucosamine.

These various forms are very similar to each other, but there is no certainty that, if they are taken as food supplements, they will have the same effects.

Scientific research has focused more on glucosamine sulphate.

As a rule, glucosamine sulphate supplements are used in the therapy of osteoarthritis and arthritis.

In many formulations, glucosamine sulphate is associated with other substances such as, for example, chondroitin sulphate, methylsulfonylmethane (MSM) and shark cartilage.

Glucosamine and chondroitin

Among the most frequent associations is that between glucosamine and chondroitin; the reason is to be found in the fact that, according to what has been reported by some research, the effectiveness of glucosamine would be greater if it is associated with chondroitin, a substance that attracts and retains the water needed to nourish and lubricate the joints.

In reality, this position is not shared by all the authors and other researches seem to show that the role of chondroitin is marginal, even taking into account the side effects (digestive disorders, vertigo, dermatitis and some rare cases of Quincke’s edema).

Glucosamine: does it work against osteoarthritis?

Although glucosamine is often presented as the anti-arthritis pill, it must be said that in reality we are still very far from a real cure for arthritic pathology: the effect of glucosamine exists, but it limits itself to blocking the pathology.

It is therefore essential for prevention, but we cannot yet speak of efficacy at a curative level.

However, this issue is further explored in the next paragraph.

Even if the rumors of the anti-arthritis effect have been overemphasized, they have had the merit of letting the general public know that osteoarthritis can be fought, slowed down and made to regress slightly with the use of simple food supplements.

Glucosamine has also been suggested in the treatment of glaucoma and even as a slimming substance, but at present there is no scientific evidence of its effectiveness in this regard.

Glucosamine: is it effective?

The NMCD (Natural Medicines Comprehensive Database) provides ratings on natural medicines based on available scientific evidence; the assessment is based on a scale ranging from 1 to 7 (1=effective, 2=probably effective, 3=possibly effective, 4=possibly ineffective, 5=probably ineffective, 6=ineffective, 7=insufficient evidence to evaluate the ‘effectiveness).

According to the NMCD, glucosamine sulfate is considered likely to be effective (scale value 2) with respect to knee osteoarthritis; possible efficacy also with regard to femoral arthrosis and that of the spine.

With regard to knee arthrosis, some studies have shown a remarkable analgesic effect, comparable to that of ibuprofen and piroxicam, even if not in terms of rapidity of effect; moreover, the effectiveness seems to refer above all to cases of non-serious arthrosis; it should also be noted that some subjects have not reported benefits from taking glucosamine sulphate.

It is believed that glucosamine is able to slow down the tearing of the joints in those suffering from osteoarthritis who take glucosamine for long periods of time.

Glucosamine sulphate is considered, again based on the NMCD scale, perhaps effective in the treatment of arthritis of the temporomandibular joint, a rather annoying inflammatory process which, in addition to pain, creates chewing problems and difficulty in articulating words correctly.

Glucosamine: administration and dosage

In general, glucosamine supplementation (3 annual cycles) is recommended for individuals who practice physical activity and are over 35 and for sedentary individuals over 45, with osteoarthritis at the onset.

As far as dosages are concerned, for the prevention of arthrosis the recommended doses (in subjects weighing between 54 and 90 kg) are 750 mg per day, usually divided into three doses.

In case of disease at an already advanced stage, these doses should be doubled.

During treatment, glucosamine dosages may change according to the progress of the disease.

Is glucosamine safe?

With regard to the safety issue, glucosamine sulphate is generally considered a safe supplement.

As with all food supplements, however, in some circumstances it is recommended to avoid taking them.

Some people have reported minor side effects such as heartburn, constipation, diarrhea, and nausea after taking glucosamine.

Although there is no evidence that taking glucosamine can cause problems in pregnant or breastfeeding women, such individuals should refrain from using glucosamine-based dietary supplements.

The same advice applies to those with asthma; there is, in fact, research that has shown a probable link between glucosamine intake and asthma attacks.

In the past, taking glucosamine was also not recommended for people with diabetes, but more recent and more reliable research suggests that glucosamine sulphate has no effect on blood sugar levels and, consequently, no problems of any kind should occur; however, as a precaution, diabetics taking glucosamine should always carefully check that no suspicious alterations occur following the intake of food supplements containing the substance in question.

Since some glucosamine sulphate products contain, among other things, lobster, crab or shrimp shells, some authors advise against the intake of such products for those who are allergic to shellfish.

However, it should be remembered that allergic reactions to shellfish are not related to the shells, but to the meat, so much so that, up to now, no cases of allergic reactions have been reported in subjects allergic to shellfish who take glucosamine.

Glucosamine and drugs

As regards interactions with other substances, the intake of glucosamine should be avoided by those taking warfarin, an anticoagulant, as various researches have shown that glucosamine sulphate enhances its action; moreover, incidentally, there are many supplements and herbal products that interact with warfarin and therefore should not be taken if this medicine is used.

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A certain amount of caution should also be used if you are taking paracetamol.

People undergoing chemotherapy should consult the specialist who is treating them before taking products containing glucosamine.

Notes on osteoarthritis

Millions of people suffer from osteoarthritis; some in a mild form, others in a severe and devastating form.

Some try to control it by taking anti-inflammatory drugs with heavy side effects, others are forced to resort to surgery.

In a healthy individual, the cartilage acts as a shock absorber and allows for smooth, even movement.

To perform its task it employs synovial fluid (an oily substance produced by the synovial membrane), which is absorbed and released by the cartilage (just like a sponge) during its operation.

During its life the cartilage wears out and the body repairs it. Under normal conditions there is a balance between damage and repair, in pathological conditions the damage and waste products described in the article on osteoarthritis prevail, causing the system to degenerate.

We speak of secondary arthrosis when it is the result of more or less repeated traumatic injuries (as in athletes) and primary arthrosis when it is essentially due to aging.

Overly optimistic rumors have been spreading for some years regarding the possibility of treating osteoarthritis using glucosamine; but, in reality, as can be understood from the above, things are a bit different.

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