Methylsulfonylmethane
Methylsulfonylmethane (MSM, or dimethylsulfone) is an organic sulfur compound belonging to a class of chemicals known as sulfones.  It occurs naturally in some primitive plants and is present in small amounts in many foods and beverages.
MSM is also known as dimethylsulfone, or DMSO2, a name that reflects its close chemical relationship to dimethyl sulfoxide (DMSO), which differs only in the oxidation state of the sulfur atom. MSM is the primary metabolite of DMSO in humans, and it shares some of the properties of DMSO.
MSM is sold as a dietary supplement that is marketed with a variety of claims and is commonly used (often in combination with glucosamine and/or chondroitin) for helping to treat or prevent osteoarthritis. Retail sales of MSM as a single ingredient in dietary supplements amounted to $115 million in 2003. Clinical research on the medical use of the chemical in people is limited to a few pilot studies that have suggested beneficial effects.

# Use as a solvent
Because of its polarity and thermal stability, MSM is used industrially as a high-temperature solvent for both inorganic and organic substances.  It is used as a medium for carrying out chemical reactions in polymerization processes as well as to make pharmaceuticals, agrochemicals, paint, coating materials and biocides. According to U.S. law enforcement officials, MSM is used to dilute methamphetamine in the illegal drug trade. 

# Effects on health
The effects of supplemental methylsulfonylmethane in biology and medicine are poorly understood. Several researchers have suggested that MSM has anti-inflammatory effects (Morton et al. 1986; Childs, 1994; Murav'ev et al., 1991). Any health effects of dimethyl sulfoxide (DMSO) may be mediated, at least in part, by MSM (Williams et al, 1966; Kocsis et al, 1975). Stanley W. Jacob, M.D., of the Oregon Health and Science University, claims to have used MSM to treat over 18,000 patients with a variety of ailments (Jacob & Appleton, 2003).
There is also criticism about the efficacy of MSM. MSM is promoted as a natural source of sulfur by the supplement and health food industry, suggesting that people are deficient in sulfur intake. However, protein in the diet is an abundant source of sulfur, which is contained in the amino acids methionine and cysteine.
Clinical evidence for the usefulness of MSM is limited to animal studies and four published clinical studies in humans. These pilot studies of MSM have suggested some benefits, particularly for treatment of osteoarthritis. Further studies would be needed to test the usefulness of the chemical as a medical therapy.

## Evidence from clinical trials
- Osteoarthritis:  After several reports that MSM helped arthritis in animal models, a double-blind, placebo-controlled study suggested that 1500 mg per day MSM (alone or in combination with glucosamine sulfate) was helpful in relieving symptoms of knee osteoarthritis (Usha and Naidu 2004).  Kim et al. then conducted a double-blind clinical trial of MSM for treatment of patients with osteoarthritis of the knee. Twenty-five patients took 6 g/day MSM and 25 patients took a placebo for 12 weeks.  Ten patients did not complete the study, and intent-to-treat analysis was performed. Patients who took MSM had significantly reduced pain and improved physical functioning, without major adverse events (Kim et al). No evidence of a more general anti-inflammatory effect was found, as there were no significant changes in two measures of systemic inflammation: C-reactive protein level and erythrocyte sedimentation rate. The authors cautioned that this short pilot study did not address the long-term safety and usefulness of MSM, but suggested that physicians should consider its use for certain osteoarthritis patients, and that long-term studies should be conducted (Kim et al. 2006).
- Seasonal Allergic Rhinitis: Barrager et al. evaluated the efficacy of MSM for hayfever (Barrager et al, 2002). Twenty-five subjects consumed 2,600 mg of MSM per day for 30 days, and a significant improvement in symptoms was observed compared to those taking a placebo. However, the study was not blinded. Also, no significant changes were observed in two indicators of inflammation (C-reactive protein and immunoglobulin E levels). The authors suggest that MSM is safe for short-term use and recommend that a larger, double-blind study be performed to establish its usefulness in treating symptoms of seasonal allergic rhinitis.
- Interstitial cystitis: In 1978, the FDA approved dimethylsulfoxide (DMSO) for instillation into the bladder as a treatment for interstitial cystitis. Since DMSO is metabolized to MSM by the body, it is possible that MSM is the active ingredient in DMSO treatments (Childs 1994).
- Snoring: Blum & Blum conducted a randomized, double-blind, placebo controlled clinical trial of an MSM-containing throat spray for snoring (Blum & Blum, 2004).

## Pharmacology and toxicity
The LD50 (dose at which 50% of test subjects are killed) of MSM is greater than 17.5 grams per kilogram of body weight. In rats, no adverse events were observed after daily doses of 2 g MSM per kg of body weight. In a 90-day follow-up study rats received daily MSM doses of 1.5 g/kg, and no changes were observed in terms of symptoms, blood chemistry, or gross pathology (Horvath et al., 2002).
Nuclear magnetic resonance (NMR) studies have demonstrated that oral doses of MSM are absorbed into the blood and cross the blood-brain barrier (Rose et al., 2000; Lin et al., 2001). An NMR study has also found detectable levels of MSM normally present in the blood and cerebrospinal fluid, suggesting that it derives from dietary sources, intestinal bacterial metabolism, and the body's endogenous methanethiol metabolism (Engelke et al., 2005).
The published clinical trials of MSM did not observe any serious side-effects of treatment, but there are no peer-reviewed data on the effects of long-term use in humans.