Side effects for glucosamine include nausea, heartburn, diarrhea and constipation, reports WebMD. Side effects for methysulfonylmethane, or MSM, include nausea, diarrhea, bloating, fatigue, headache, insomnia, itching and worsening of allergy symptoms.
Glucosamine, which is often harvested from shellfish, is most commonly used to treat arthritis, although researchers have found various other uses for the compound, according to WebMD. These uses include treatment of glaucoma and stimulation of weight loss. Glucosamine is important to the body for building tendons, ligaments, cartilage and joints.
Methylsulfonylmethane has a variety of uses that impact multiple regions of the body, states WebMD. It is typically used to treat chronic pain caused by inflammation. However, its alternate uses range from combating muscle spasms and hair loss to diminishing scar tissue and stretch marks. It's even been shown to be useful in treating Alzheimer's disease, as well as prostate and breast cancer. Methylsulfonylmethane is believed to work by providing sulfur for the synthesis of other chemicals in the body.
Glucosamine and methylsulfonylmethane are both naturally occurring compounds, although they can be synthesized in laboratories, explains WebMD. Both compounds are well known for their health benefits and are considered safe to use for up to two months and three months, respectively. They are believed by some to work best in conjunction, and as a result can often be found together in dietary supplements.