1.5–3 g/day.
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Methylsulfonylmethane, known almost universally by its acronym MSM, is an organic sulfur compound naturally present in plant and animal foods in very small concentrations, and in significant amounts as an isolated supplement at doses of grams per day; it is the oxidized metabolite of dimethyl sulfoxide (DMSO), a solvent with a long history of clinical and veterinary use, and it forms part of the natural dietary supply of sulfur, a structural element essential for the synthesis of sulfur-containing amino acids, glutathione, keratin, and the components of the extracellular matrix of cartilage and connective tissue.
The popularity of MSM as a joint and anti-inflammatory supplement grew enormously from the 1990s onward, driven by popular books and by veterinary clinical observation with DMSO; although the human clinical evidence is moderate and heterogeneous, there is a growing body of randomized trials confirming modest but replicable effects in osteoarthritis and, to a lesser extent, in post-exercise musculoskeletal pain and in some chronic inflammatory conditions.
The indication with the best clinical evidence is symptomatic osteoarthritis, especially of the knee: several randomized trials have shown significant reductions in pain and stiffness scores (WOMAC, VAS) with doses of 3-6 grams daily for 12-24 weeks, with an efficacy profile lower than that of pharmacological anti-inflammatories but sufficient as an adjunct or as an alternative for people with a contraindication to conventional anti-inflammatories because of gastrointestinal, renal, or cardiovascular risk.
A randomized trial published in 2006 with 50 patients with knee osteoarthritis showed that 6 grams of MSM daily for 12 weeks significantly reduced pain and improved physical function compared with placebo; combinations of MSM with glucosamine and chondroitin (the three classic joint supplements) appear to offer additive benefits in some studies, a multimodal strategy common in clinical practice.
In delayed-onset muscle soreness (DOMS), several small studies have shown significant reductions in pain and in markers of muscle damage (creatine kinase, lactate dehydrogenase) with supplementation at 3 grams daily for several days before and after intense exercise; the effects are modest but consistent with a general anti-inflammatory and antioxidant profile.
In seasonal allergic rhinitis, a randomized trial with 50 patients showed significant improvements in nasal and ocular symptoms with 2.6 grams of MSM daily for 30 days, a less classic indication but with a plausible mechanism via modulation of the histamine-mediated inflammatory response.
The doses studied range from 1,500 to 6,000 milligrams daily, divided into two or three doses with meals to improve digestive tolerance; the effect on joint pain and stiffness appears gradually, typically from the fourth week onward, and requires maintaining treatment for at least 12 weeks to assess the full response; combinations with glucosamine/chondroitin or with curcumin are common in commercial joint formulations.
It is one of the supplements with the best safety profile: practically no adverse effects at the doses studied and no specific contraindications; the adverse effects described are rare and mild (digestive discomfort, headache, fatigue at the start of treatment that usually disappears on its own); people taking anticoagulants such as warfarin should exercise theoretical caution because of a possible mild potentiation that has been described; in pregnancy and breastfeeding the data are limited, although no relevant adverse effects have been described with use at usual doses.
Information, not medical advice. Scientific evidence reflects the quality of the studies.