The principle behind glucosamine supplementation is that the glucosamine is delivered to the joint space and incorporated into proteoglycans of joint cartilage to maintain structure and repair damage. Glucosamine may also stimulate chondrocytes (cartilage cells) to begin producing healthy new cartilage matrix (both collagen and proteoglycans).
There are numerous European studies showing a clear benefit of glucosamine supplements for relief of joint pain and stiffness associated with arthritis. Many of the studies have been criticized for lack of scientific control, short duration and small size, but recent meta-analyses of the smaller studies have supported the beneficial role of glucosamine supplements as a safe and effective approach to treating osteoarthritis. In general 1-3 months of glucosamine supplementation seems to be more effective than a placebo and at least as effective as analgesic and non-steroidal anti-inflammatory drugs (NSAID), like acetaminophen and ibuprofen, in reducing the joint pain of osteoarthritis. Until more rigorous studies are conducted in the United States, the Arthritis Foundation has stated that it cannot recommend glucosamine supplements as a treatment for osteoarthritis, but this stand has not stopped the Foundation from accepting financial support from the producer of the best selling brand of glucosamine supplements on the market – Rexall Sundown’s Osteo-Bi-Flex. Perhaps the supplements with the best clinical substantiation are Dona from Rotta Labs and Cosamin from NutraMax Labs.
Occasional symptoms of gastrointestinal discomfort have been noted, but no significant adverse effects have been noted with glucosamine supplementation. Although there have been no long-term safety studies conducted in humans, animal studies on glucosamine have found it to be non-toxic. Diabetics may want to exercise a degree of caution when using glucosamine supplements, as there have been several animal studies and one small human pilot study that have suggested an increase in blood sugar levels during regular glucosamine consumption (though most of the animal studies have used injections of glucosamine).
Glucosamine supplements tend to be among the more expensive products on the shelf. A one-month supply of capsules can range from $15 to well over $100. Because they have to be consumed for 1-3 months before any noticeable benefit is apparent, you may need to invest a significant amount of money before you realize any benefits. However, because arthritis pain is one of the most debilitating conditions, most people dealing with such pain would gladly invest a dollar or so per day in a supplement that relieved their discomfort and helped repair their damaged cartilage tissue. For people with existing chronic joint pain, glucosamine supplements are probably worth the significant dollar investment for the benefits that they deliver. For those individuals with intermittent joint pain or those with more mild joint stiffness, the high cost associated with glucosamine supplements may not be justified - and the money might be better spent on other more relevant supplements.
No dose-response studies have been conducted with glucosamine supplements. Virtually all oral supplementation studies on glucosamine have used 1500mg per day - usually in 3 divided doses of 500mg each. While this level appears to be an effective dose, there is no information to suggest that a higher does would work better or faster - or that a lower dose would be less effective. A common supplementation strategy, which can decrease the daily cost of supplements, is to consume 1500mg of glucosamine per day for the first 60-90 days of your regimen, followed by a reduced intake of 250-750mg per day as a "maintenance level." Following the initial 60-90 day period, dosage levels can be increased or decreased based on individual pain and stiffness levels.