Methylsulfonylmethane

Methylsulfonylmethane (MSM) is an organosulfur compound with the formula (CH3)2SO2. It is also known by several other names including DMSO2, methyl sulfone, and dimethyl sulfone. This colorless solid features the sulfonyl functional group and is considered relatively inert chemically. It occurs naturally in some primitive plants, is present in small amounts in many foods and beverages, and is marketed as a dietary supplement. It is also commonly found in the atmosphere above marine areas, where it is used as a carbon source by the airborne bacteria Afipia.

Structure and chemical properties
MSM and the corresponding sulfoxide dimethyl sulfoxide ((CH3)2SO, DMSO) have different physical properties. MSM is a white crystalline solid at STP (m.p. = 109 °C) whereas DMSO is a liquid under standard conditions. The sulfoxide is a highly polar aprotic solvent and is miscible with water; it is also an excellent ligand. MSM is less reactive than DMSO because the S-atom of the sulfone is already in its highest oxidation state (VI). Indeed oxidation of the sulfoxide produces the sulfone, both under laboratory conditions and metabolically.

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 in organic synthesis. For example, displacement of aryl chlorides by potassium fluoride can be usefully conducted in molten MSM. With a pKa of 31, it can be deprotonated with sodium amide, and the conjugate base is an effective nucleophile.

Other uses
Although no medical uses for MSM have been approved by any government, a variety of health benefits have been claimed and studied. Stanley W. Jacob reported having administered MSM to over 18,000 patients with a variety of ailments; he co-authored a book promoting MSM with a variety of claims, including a utility as a natural source of "biologically active sulfur," suggesting that people are deficient in such forms of sulfur in their dietary intake. There is no Dietary Reference Intake (DRI) or Daily Value established for sulfur and sufficient dietary sources are readily available in onions, garlic and cruciferous vegetables and in protein-containing foods, including nuts, seeds, milk and eggs (whites and yolks).

The claims for the need for sulfur supplementation originate with Robert Herschler, a biochemist who patented "Dietary and pharmaceutical uses of methylsulfonylmethane and compositions comprising it" in 1982; he claimed that MSM was useful in stress, mucous-membrane inflammation, allergies and gastrointestinal conditions.

MSM is sold as a dietary supplement and marketed with a variety of claims, often in combination with glucosamine and/or chondroitin for helping to treat or prevent osteoarthritis. According to one review, "The benefits claimed [for MSM] far exceed the number of scientific studies. It is hard to build a strong case for its use other than for treating arthritis problems."

Moreover, in cases involving topical therapeutics, the role of MSM as an active agent, per se, versus its having a role in promoting skin permeation (in manner, akin to its solvent relative DMSO) must be characterized/controlled. The biochemical effects of supplemental methylsulfonylmethane are poorly understood. Some researchers have suggested that MSM has anti-inflammatory effects. The spectrum of biological effects of dimethyl sulfoxide (DMSO) and MSM differ, but those of DMSO may be mediated, at least in part, by MSM.

Herschler's patent documents, and much of the alternative medical literature supporting MSM use, claim that "the average diet is deficient in methylsulfonylmethane because it is readily lost during conventional food processing, such as frying, dehydrating, dilution with synthetic fillers and other poorly nutritional additives, cooking, radiation or pasteurizing, and long-term storage". According to Quackwatch, "this statement is absurd, because the amount of sulfur in protein foods is not affected by processing. Since Americans tend to consume more protein than they need, "sulfur deficiency" is very unlikely and would not occur without obvious evidence of severe malnutrition. If it could occur, the remedy would be to eat adequate protein, not to supplement with MSM".

FDA enforcement action
In October 2000, the United States Food and Drug Administration warned one MSM promoter, Karl Loren, to cease and desist from making therapeutic claims for MSM, as the marketing of drugs without the approval of the FDA is illegal.

Evidence from clinical trials
Small-scale studies of possible treatments with MSM have been conducted on both animals and humans. These studies of MSM have suggested some benefits, particularly for treatment of osteoarthritis. An extensive list of MSM and DSMO peer reviewed studies is included in S. Parcelli's article "Sulfur in Human Nutrition and Applications in Medicine", Parcell, S., Alternative Medicine Review, 2002; 7(1):22-44.

Osteoarthritis
A review by S. Brien, P. Prescott, N. Bashir, H. Lewith, and G. Lewith of the two small randomized controlled trials of methylsulfonylmethane in osteoarthritis knee pain relief "reported significant improvement in pain outcomes in the treatment group compared to comparator treatments; however, methodological issues and concerns over optimal dosage and treatment period were highlighted."

The two trials included 168 people, of whom 52 received the drug. The review authors state: "No definitive conclusion can currently be drawn" and there is "no definitive evidence that MSM is superior to placebo in the treatment of mild to moderate osteoarthritis of the knee." While one of the two studies suggests that taking MSM for 12 weeks or less may be safe, "further research is needed to assess its safety for long-term use." Side effects of MSM ingestion include stomach upset, diarrhoea, and headache. In the absence of studies into dosage, longer-term safety, and definitive efficacy trials, MSM must be considered experimental and should not be self-administered or prescribed outside clinical trials.

After several reports that MSM helped arthritis in animal models, one study by P.R. Usha et al. had suggested that 1.5 g per day MSM (alone or in combination with glucosamine sulfate) was helpful in relieving symptoms of knee osteoarthritis.

Kim et al. conducted a second 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 intention to treat analysis was performed. Patients who took MSM reported reduced pain and improved physical function, but no evidence was found of a more general anti-inflammatory effect; there were no significant changes in two measures of systemic inflammation: C-reactive protein level and erythrocyte sedimentation rate.

Interstitial cystitis
In 1978, the FDA approved dimethyl sulfoxide (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.

Other conditions
Barrager et al. evaluated the efficacy of MSM for hay fever. Fifty-five subjects consumed 2.6 g of MSM per day for 30 days. This study was not blinded and did not include controls; while an improvement in symptoms was observed compared to initial baseline, no significant changes were observed in two indicators of inflammation (C-reactive protein and immunoglobulin E levels).

Blum & Blum also conducted a double-blind, placebo-controlled clinical trial of an MSM-containing throat spray to reduce snoring.

Pharmacology and toxicity
The (dose at which 50% of test subjects are killed by the high dosage) 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.

Nuclear magnetic resonance (NMR) studies have demonstrated that oral doses of MSM are absorbed into the blood and cross the blood–brain barrier. 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.

Published clinical trials of MSM did not report any serious side effects, but there are no peer-reviewed data on the effects of its long-term use in humans.