MSM for arthritis pain: Any harm in long-term use?

Very few studies have examined long-term effects of the dietary supplement called methylsulfonylmethane (MSM). One study suggested that it's safe to take MSM for up to 30 days. But further research is needed to assess its safety for long-term use.

MSM occurs naturally in some fruits, vegetables and grains. But it's also sold as a dietary supplement. Manufacturers of these supplements have touted MSM as a treatment for a variety of conditions, including chronic pain, arthritis, headaches, asthma, sinusitis, constipation and Alzheimer's disease.

However, only a few clinical trials have looked at the possible effectiveness of MSM in treating these conditions in humans. One small study suggested that MSM may relieve pain due to osteoarthritis. A couple of other studies suggested it may reduce symptoms of hay fever (allergic rhinitis).

Although there is great interest in using MSM to treat a variety of conditions, little evidence supports either its benefits or safety. Potential side effects of taking MSM include stomach upset, diarrhea and headache.

As with most dietary supplements, research trials involving MSM have generally been small in size and of relatively short duration. Keep this in mind as you make decisions regarding the use of dietary supplements.