Introduction
Osteoarthritis is associated with factors such as ageing,
obesity and physical injury (sport or otherwise), all
of which can contribute to degeneration of joint cartilage. Commonly,
analgesics (aspirin, paracetamol or more potent drugs such as
morphine) and anti- inflammatory agents (e.g. ibuprofen) are used
in the management of osteoarthritis. However, studies have shown
that glucosamine sulphate can provide relief from arthritic pain
related symptoms but without the side effects of commonly used
drug therapies.
Although glucosamine sulphate is approved as a prescription drug
for osteoarthritis in some European Union countries, there is
still uncertainty about glucosamine's efficiency in the medical
community in the UK and USA. This article aims to highlight why
this uncertainty exists and to present an overview of this dietary
supplement.
What is Glucosamine Sulphate?
Glucosamine is a combination of a protein and a sugar and is
substance that occurs naturally in the connective tissues and
cartilage joints. Most, if not all, scientific studies with glucosamine
refer to the formulation of glucosamine sulphate
and when sold as a dietary supplement this is usually combined
with Chondroitin Sulphate. Chondroitin is found
in and around the cartilage cells and it has been suggested that
this supplement may help repair some of the damaged joint.
Osteoarthritis is not yet fully understood but it is thought
to be the destruction of cartilage, possibly due to loss of collagen
and proteoglycans. It has been suggested that glucosamine helps
regenerate damaged cartilage as glucosamine is needed to make
proteins (proteoglycans), which are the building blocks of cartilage.
Along with collagen (a fibrous protein that makes up the connective
tissue), these proteins provide the strength and support of the
joint. Glucosamine also pulls water into the cartilage (to maintain
the 70% water content of cartliage) producing a gel like sac providing
cushioning and flexibility in the joint. Therefore, in essence
supplementation is thought to magnify the bodies natural level
of glucosamine.
The supplements sold are execrated from animal tissue with glucosamine
taken from crab, lobster or shrimp shells, although it can also
be chemically synthesized. It is typically sold as oral tablets
or capsules with the most common commercial compounds being glucosamine
sulphate, N-actyl-glucosamine and glucosamine hydrochloride. Chondroitin
sulphate is extracted from animal cartilage such as tracheas or
shark cartilage.
What is the evidence?
A study published in the Lancet (medical journal) in 2001 show
that glucosamine effectively controlled osteoarthritis symptoms
and even suggested that it produced some reversal of the disease
process. More recently (2003) scientists reviewed the reported
effects of 15 studies using either glucosamine or/and chondroitin
on osteoarthritis of the knee and found treatment with either
glucosamine or glucosamine plus chondroitin to be effective. This
study even concluded that supplementation will improve joint mobility
for 1 in 5 patients and may slow narrowing of joint spaces. However,
the authors of this review study and other review studies have
noted a likely publication bias but also some degree of efficiency
appears prominent for these preparations.
Furthermore, all these clinical studies of glucosamine in arthritis
of the knee or hip, note that:
- Onset of reduced symptoms does not occur for several weeks
after starting glucosamine
- Benefits persist for several weeks or months after glucosamine
is discontinued
- No reports that continued use reduces the impact or efficiency
However, caution is recommended for long-term use as although
there is no basis for concern currently, it would not be surprising
some eventually emerge.
The evidence appears promising, so why is there reserves
about its efficiency?
Systematic reviews of studies have found that many of the clinical
trials testing complementary or alternative medicines have major
flaws. These are due to bias from large company sponsorship, poor
quality of research and small number of people being tested in
the studies.
As almost all original glucosamine studies suffered from problems
with bias and quality, all the results must be treated with caution
until larger better-designed studies are carried out to allow
an authorised recommendation. However, due to the large amount
of research pointing towards glucosamine being a safe and effective
treatment many medically qualified persons do recommend its use
for osteoarthritis sufferers.
Are there any studies currently happening without major
flaws in its design?
The answer to this is yes but unfortunately it will be another
couple of years before the results will be published. The study
is called The
Glucosamine-Chondroitin Arthritis Intervention Trial (GAIT)
and it is the first multicentre clinical trail in the US to test
the effects of glucosamine and chondroitin supplements for treatment
of knee osteoarthritis. The study is currently testing whether
glucosamine and chondroitin, used separately or in combination,
are effective in reducing pain and improving functional ability
in patients with knee osteoarthritis.
An additional study is to assess whether glucosamine and chondroitin
can reduce or halt the progression of knee osteoarthritis and
the fundamental task of this study is to put to rest if Glucosamine
and Chronditin are effective or not.
Is it beneficial for athletes with injuries of the joint to
use?
A study in the British Journal Sport Medicine (2003) gave subjects
with regular knee pain, 12 weeks of a glucosamine supplement (2000mg
per day). The results suggested that a glucosamine supplement
can provide some degree of pain relief and improved mobility in
subjects who experience regular, chronic knee pain due to cartilage
damage and/or possible osteoarthritis. 88% of the glucosamine
group did report less knee pain, however there were no objective
improvements between groups in the functional tests. This study
supports the findings from other reports but you should note that
this study was not specific to athletes and it was only self reported
improvements in knee pain.
Are there any side effects or cautions?
- As yet minimal side effects have been noted in rare reports
in complementary medicine books and websites. These include
skin rashes, headaches, downiness and mild stomach symptoms
such as diarrhoea and flatulence. The long-term effects from
use of glucosamine are not yet know.
- People who are allergic to the chitin in shellfish from which
glucosamine is extracted should be wary. Although, most allergies
are caused by proteins in shellfish and not the chitin (the
carbohydrate from which glucosamine is extracted) such individuals
should always consult with their doctor.
- Children, and women who are pregnant or breastfeeding should
avoid using glucosamine, as the effects are not known in these
populations.
- There has been a concern raised whether glucosamine raises
blood sugar levels in diabetics. Although the evidence for this
is inconclusive, do check with your doctor if you have impaired
glucose intolerance or are diabetic.
If I decide to take glucosamine &/or chrondition sulphate
supplement what do I look for?
Dietary supplements are unregulated therefore the quality and
contents will vary. If you do decide to take these I would recommend
that you:
- Consult your doctor (your pain may not be caused by osteoarthritis
or joint pain) and you may be on medications and your doctor
does not want you to add this.
- Choose products that are sold by large well established companies.
- Read the product to make sure the list makes sense to you.
The amount used in studies is 1500mg-2000mg per day and in studies
of chondroitin sulphate 1200 mg per day. If you don’t experience
any difference in symptoms within 3 months, you will probably
not get any relief from the supplements.
Summary
- If you are to use glucosamine sulphate you should understand
that research on the effectiveness
of glucosamine is still inconclusive.
- Athletes with cartilage damage should keep in mind that there
is no evidence that this supplement works in athletes with cartilage
damage. Therefore its use is mainly due to media reports and
'hear say' in athletic populations. Check with a sports medicine
doctor to see if you have appropriate clinical signs and symptoms.
- As yet there are minimal known side effects but the long-term
effects are not yet known.
- You should inform your doctor especially if you are taking
other drugs due to potential drug-drug interactions or have
a medical condition (see cautions).
Definitions (Oxford Medical Dictionary (1998) & Oxford Dictionary
of Chemistry (1996))
Osteoarthritis - A degenerative disease of
joints resulting from wear of the articular cartilage. The joints
are painful and stiff with restricted movement. It is recognized
on x-ray by narrowing of the joint space (due to loss of cartilage).
People who suffer from severe cartilage damage of the joints can
progress to this degenerative condition.
Chondroitin Sulphate – A combination of
a protein and a sugar that forms an important constituent of cartilage,
bone and other connective tissues.
Connective tissue - Protects and connects cells
or organs. All types of connective tissue contain protein fibres
that are either tough or elastic.
Cartilage – A tough connective tissue.
In some joints it is the main cushion between the bones. In joints
with synovial sacs (see below), it covers the ends of the bones
and is called articular cartilage.
Synovial sac- A cushioning bag of lubricating
fluid of elastic connective tissue. For example, there is a synovial
sac in the knee joint.
References
Blakeley JA & Iberia VEO (2004). Glucosamine & Osteoarthritis.
American Journal of Nursing; 104 (2): 54-59.
Braham R, Dawson B, Goodman C (2003). The effect of glucosamine
supplementation on people experiencing regular knee pain. British
Journal of Sports Medicine; 37:45-49.
Chard J, Dieppe P (2001). Glucosamine for osteoarthritis: magic,
hype, or confusion? British Medical Journal; 322: 1439-1440.
McAlindon TE, La valley MP, Gulin JP, Felson DT (2000). Glucosamine
and chondroitin for treatment of osteoarthritis. Journal of American
Medical Association; 283 (11): 1469-475
Nahin RL, Straus SE (2001). Research into complementary and alternative
medicine: problems and potential. British Medical Journal; 322:
161-164.
Ricky F, et al (2003). Structural and symptomatic efficacy of
glucosamine and chondroitin in knee osteoarthritis. A comprehensive
meta-analysis. Archives of Internal Medicine; 163 (13): 1514-1522.
Rovati L C, Annefeld M, Giacovelli G, Schmid K, Setnikar I (1999).
Correspondence: Glucosamine in osteoarthritis. Lancet; 354 (6):
1641-1642.
Web sites
The
Arthritis Foundation
The National
(American) Center for Complementary and Alternative Medicine
Australia
Institute of Sport – Sports Supplement Program 2004
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