The natural glucosamine levels in the body drop as people age, and this can lead to gradual deterioration of the joints. This is why it has become common practice to take glucosamine sulfate supplements to counteract this effect, although experts aren’t sure exactly how they work.

Glucosamine has been shown in some studies to help ease the pain of mild to moderate osteoarthritis of the knee, and it may also help with other joint pain caused by osteoarthritis.

Glucosamine has also been used to try and treat rheumatoid arthritis and other conditions, such as inflammatory bowel disease, asthma, allergies, chronic venous insufficiency, sports injuries, temporomandibular joint problems (TMJ), chronic low back pain, and many others. So far, these uses of glucosamine are not well supported by evidence from research studies.

For osteoarthritis, the typical dose of glucosamine used in most studies was 500 milligrams of glucosamine sulfate taken three times a day - but you should ask your doctor about specific dosing. Some experts recommend taking them with meals to prevent stomach upset.

Although glucosamine sulfate supplements are often manufactured from the outer shells of shellfish, there aren't any natural food sources of it.