Supplements are made from the shells of shellfish such as lobsters and shrimp, or synthetically. Image Credit: Eugeniusz Dudzinski/iStock/GettyImages

Glucosamine sulfate supplements are taken to ease joint pain caused by osteoarthritis and rheumatoid arthritis. Natural sources of glucosamine are limited mostly to the shells of shellfish; these are commonly used to make glucosamine supplements, although supplements can also be synthesized in a laboratory.

Tip There are no natural sources of glucosamine in food. Supplements are made from the shells of shellfish such as lobsters and shrimp, or synthetically.

There are different forms of glucosamine including glucosamine sulfate, glucosamine hydrochloride and N-acetyl glucosamine. Most of the scientific research on glucosamine has involved glucosamine sulfate.

Natural Sources of Glucosamine

Glucosamine is a natural compound found in healthy cartilage — the tough tissue that cushions joints — and particularly in the fluid around the joints. For dietary supplements, it is harvested from shells of shellfish or is made synthetically in a laboratory.

There are no natural food sources of glucosamine other than shellfish shells, such as those from shrimp, lobster and crab. However, there are many supplements available. You will often see glucosamine sold in combination with chondroitin sulfate in a supplement form.

The Arthritis Foundation lists a recommended dosage of 1,500 milligrams per day, whether you take glucosamine capsules, tablets, liquid or powder (mixed into a drink).

A 2016 article published on the National Capitol Poison Control website notes that glucosamine is a dietary supplement, not a medicine, and as such the FDA does not regulate its effectiveness, safety or labeling. Some glucosamine products have been found to contain less or more glucosamine than was listed on the label. In other cases, the product was found to be contaminated, according to the article.

Glucosamine for Joints

The National Library of Medicine writes that taking glucosamine sulfate can provide some pain relief for those suffering from osteoarthritis, particularly osteoarthritis of the knees, although not enough to prevent the need of pain medication during flare ups.

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Still, evidence is inconclusive as to whether this supplement is actually effective. A July, 2016 trial studied chondroitin sulfate and glucosamine sulfate combination therapy to reduce joint pain and functional impairment in patients with symptomatic knee osteoarthritis over 6 months. The study did not find any real reduction of joint pain among users, as compared with those taking a placebo.

There are many conditions for which glucosamine sulfate supplements are recommended with little scientific backing, in addition to osteoarthritis. These include:

Joint pain caused by drugs called aromatase inhibitors (aromatase inhibitor-induced arthralgias).

Heart disease.

Knee pain.

Multiple sclerosis.

Recovery after surgery.

Stroke.

Jaw pain.

A group of eye disorders that can lead to vision loss (glaucoma).

Joint pain.

Painful bladder syndrome.

Weight loss.

Drawbacks to Glucosamine

In general, glucosamine and glucosamine supplements are believed to be safe for most people. Potential risks, according to Harvard Health Publishing, include diarrhea and abdominal pain, heartburn, drowsiness, headaches and allergic reactions, especially for people with an existing allergy to shellfish. Other side effects could include nausea, constipation or skin reactions.

In addition, there are several different kinds of glucosamine products on the market. Research showing benefits usually relates to glucosamine sulfate while, products that contain glucosamine hydrochloride are generally found to be less effective.

Dietary supplements that contain glucosamine often also contain additional ingredients. These can include chondroitin sulfate, methylsulfonylmethane (MSM) or shark cartilage, but there is, as yet, no conclusive scientific evidence that these other ingredients add any benefit to the perceived benefits of glucosamine.