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Glucosamine is a dietary supplement that is typically produced from chitin, a compound found in the hard outer shell of crabs, lobsters, shrimp and other shellfish. This popular dietary supplement is also available in a vegetarian form. Although such corn-derived supplements may be more suitable for your diet, they present issues that are both unique to vegetarian sources and common to all forms of glucosamine.

Vegetarian Glucosamine

Glucosamine is a naturally occurring sugar in the human body that serves as one of the building blocks of joint cartilage. As a result, glucosamine supplements are typically used to help rebuild cartilage and treat arthritis. Despite mixed evidence for its effectiveness, glucosamine is one of the most commonly used dietary supplements in the U.S. These supplements typically contain shellfish, thus making them unsuitable for vegetarians and unsafe for those with allergies. Although corn-derived sources do not present such issues, the use of vegetarian glucosamine can potentially result in numerous adverse side effects.

General Side Effects

Vegetarian sources of glucosamine share numerous side effects with those derived from shellfish. As drowsiness is among the most common, you should avoid driving, operating heavy machinery or doing anything else that might be dangerous while drowsy. Other common side effects of both sources of glucosamine include constipation, diarrhea, heartburn, nausea, headaches, upset stomach and vomiting. Although these do not commonly become major issues, you should stop taking glucosamine and seek medical attention if these side effects become severe and persistent. In addition, you should avoid glucosamine entirely if you are pregnant or breast-feeding.


Despite being less allergenic than shellfish, corn is increasingly being recognized as a source of food allergies. In fact, approximately 2 percent of people report experiencing some form of allergic reaction to corn. Common symptoms of a corn allergy are similar to those of other food allergies, including hives, rashes, nausea, sinus problems, headaches, vomiting, diarrhea and breathing difficulties. As an allergic reaction to corn can result in life-threatening anaphylaxis, you should avoid vegetarian glucosamine if you have any reason to suspect that you have a corn allergy.

Other Issues

Glucosamine supplements are not regulated by the U.S. Food and Drug Administration. As a result, many glucosamine supplements do not accurately list their ingredients. In fact, research into their contents indicates that such products contain anywhere from no glucosamine to over 100 percent of the amount listed on the package. With no clear indication of the contents of such products, you should consult with a health professional before starting glucosamine supplementation to discuss the most effective and safest option for you.