For many years, veterinarians routinely gave glucosamine to racehorses to help preserve their joints over years of pounding the track. Now scientists are studying whether glucosamine, a compound that your body uses to make cartilage, can help people as well.
For more than 40 years, European researchers have been studying whether taking glucosamine in supplement form can help relieve arthritis pain and rebuild eroded cartilage. Although the evidence looked promising in the 1990s, several recent show that glucosamine and chondroitin -- a combination taken by millions -- do nothing to relieve arthritis pain.
A 2018 meta-analysis found no significant pain relief. And in a 2010 analysis of data from 10 previous studies, researchers at the University of Bern, Switzerland, concluded that the supplements performed no better than placebos (sugar pills) in thwarting pain. The researchers said that if patients found benefits in taking glucosamine and chondroitin, they need not stop. There was no harm found. But they recommended against patients beginning a regimen.
Other studies have backed up those conclusions. In a 2005 analysis, researchers at Queen's University in Ontario, Canada, found that glucosamine showed no benefit, either in controlling pain or in joint function for patients with osteoarthritis.
What are the types of glucosamine?
There are three salt forms (types) of glucosamine: Glucosamine sulfate, glucosamine hydrochloride and n-acetyl glucosamine. Glucosamine sulfate is the best studied of the three. Older studies in humans found glucosamine sulfate reduced pain and improved function in people with knee osteoarthritis.
In some studies it worked as well as non-steroidal anti-inflammatory drugs (NSAIDs). At least two studies found it helped maintain knee cartilage, something NSAIDs don't do. However, one study found it didn't help a group of older, heavy men who had knee osteoarthritis for more than 10 years. There is limited evidence from human trials that glucosamine sulfate may help with osteoarthritis in other joints.
Glucosamine hydrochloride did not reduce pain in one 8-week study of people with knee osteoarthritis. A combination of glucosamine hydrochloride, chondroitin sulfate and manganese reduced knee osteoarthritis pain in two human studies. But it is unclear if the benefit was from one, two or all three ingredients. N-acetyl glucosamine has not been studied in human osteoarthritis.
How does it work?
The theory is that people with arthritis may not produce enough glucosamine, and that taking glucosamine supplements might help restore the cartilage that has eroded away between arthritic joints. In one study, researchers traced radioactively labeled glucosamine in the body and found that joint cartilage was indeed absorbing it. Some researchers speculate that the sulfate portion of glucosamine sulfate may be important for its anti-arthritis effects.
How safe is it?
In studies, glucosamine rarely caused side effects, and then only mild ones such as nausea, diarrhea, constipation, and heartburn. However, no studies of glucosamine on pregnant women, children, and the very elderly have been done, so those populations should avoid glucosamine unless it is recommended by a doctor. Researchers speculate that glucosamine may be less risky than NSAIDs, which can cause stomach bleeding and even liver or kidney damage with long-term use. Glucosamine sulfate has been used safely in human studies lasting up to three years.
Some glucosamine products are made from the shells of shellfish, so people with shellfish allergy should talk with their doctor before trying it. Also, evidence suggests that glucosamine may cause insulin resistance, so people with diabetes should talk with their doctor before using glucosamine.
How is it taken?
There are many glucosamine products available containing one or more of the three salt forms. Look for products that contain only glucosamine sulfate, the salt form shown to help knee osteoarthritis in people. A typical dose is 500 milligrams (mg) three times daily, or 1500 mg once daily.
One combination product, Cosamin DS (containing glucosamine hydrochloride, chondroitin sulfate and manganese) seems to help reduce knee arthritis pain. Keep in mind, the government doesn't regulate supplements as strictly as it does drugs, so quality and potency can vary from product to product. In rare cases, products may be contaminated with undesirable substances. If you decide to take glucosamine, ask a pharmacist or naturopath to recommend a reputable brand.
The Latest on Glucosamine/Chondroitin Suuplments, Harvard Health Letter, September 2019
"Glucosamine therapy for treating osteoarthritis," April 18, 2005, National Institutes of Health
Reginster JY, et al. Long-term effects of glucosamine sulphate on osteoarthritis progression: a randomised, placebo-controlled clinical trial. Lancet 2001;357(9252):251-56.
Carol J. Henderson, PhD, RD, Dietary Outcomes in Osteoarthritis Disease Management.