Benefits
Osteoarthritis pain and function
Several small randomized trials in knee osteoarthritis report modest improvements in pain or physical function with MSM, but a pooled analysis of three higher-quality trials, two testing the related compound DMSO and only one testing MSM, found no statistically significant effect on pain. Effect sizes are small, and MSM is best viewed as optional adjunct support rather than a proven treatment.
Exercise soreness and recovery
In a placebo-controlled half-marathon trial in 22 runners, 3 g/day MSM did not significantly reduce blood markers of muscle damage (creatine kinase, lactate dehydrogenase) or oxidative stress, and the lower post-exercise muscle and joint soreness in the MSM group did not reach statistical significance. Two small placebo-controlled reports in 18 men who ran 14 km found lower creatine kinase and oxidative-stress markers with MSM.
Sulfur for connective tissue
MSM provides bioavailable sulfur required for joint cartilage, collagen, and other connective tissues. This is the rationale for its joint health use, but whether MSM's sulfur improves connective tissue in people has not been shown.
Anti-inflammatory activity (mechanistic)
Anti-inflammatory activity is seen in animal and cell studies, but human oral-MSM trials have not demonstrated reductions in blood inflammatory markers such as CRP or IL-6. Any anti-inflammatory benefit in people remains unproven.
Skin, hair, and nails (limited evidence)
Sulfur is a building block for keratin (hair and nails) and collagen (skin). In one manufacturer-affiliated study, 3 g/day of oral MSM for 16 weeks reduced facial wrinkles and skin roughness versus placebo in 20 people, and a 63-person phase without placebo reported improvements at 1 or 3 g/day. No trials of oral MSM for hair or nails are cited here.
Sulfur and glutathione (mechanism only)
MSM supplies sulfur that the body can use to make glutathione, the main antioxidant inside cells. This is the proposed reason for the exercise results in the oxidative stress benefit below, but it remains a theoretical link: blood glutathione rose with MSM in one small trial and did not change in a pilot study.
Combination with glucosamine
In one randomized trial, MSM combined with glucosamine reduced knee osteoarthritis pain and swelling more than either agent alone over 12 weeks. That trial did not include chondroitin, so combinations adding chondroitin are less directly supported.
Good tolerability in short-term trials
In placebo-controlled trials lasting up to 16 weeks, MSM at 1.5 to 6 g/day was well tolerated. One 16-week trial at 6 g/day found no differences from placebo in blood counts, liver and kidney markers, weight, or blood pressure. Longer-term use has not been tested in the trials cited here.
Oxidative stress markers after hard exercise, in small trials
Two placebo-controlled reports from one research group each gave 18 young men 50 mg/kg/day MSM or placebo for 10 days before a 14 km run. MSM kept malondialdehyde, protein carbonyls and oxidized glutathione lower, raised reduced glutathione, and raised total antioxidant capacity. In a half-marathon trial in 22 runners, 3 g/day did not lower oxidative-stress markers versus placebo. These are small trials of blood markers.
Mechanism of action
Sulfur donation
MSM provides sulfur that may be used to make methionine, cysteine, glutathione, and sulfur-containing structural proteins (keratin, collagen). This is the rationale for its skin, hair, nail, and antioxidant uses, but in the cited exercise trials that measured it, blood glutathione was higher with MSM in one and did not change in another. Whether extra sulfur from MSM benefits well-nourished adults has not been shown.
Anti-inflammatory signaling
MSM modulates NF-κB signaling and reduces inflammatory cytokines (TNF-α, IL-6) in animal and cell studies. No human trial of oral MSM has shown a reduction in CRP or IL-6, so this is mechanistic, not a demonstrated human effect. Mechanism plausible but clinical effect sizes modest compared to mechanism-based predictions.
Antioxidant via glutathione support
MSM is proposed to support glutathione synthesis by supplying sulfur for cysteine; glutathione is the main antioxidant inside cells. Human exercise trials are mixed. MSM did not lower oxidative-stress markers after a half-marathon, and blood glutathione did not change in a small pilot, although antioxidant capacity (TEAC) rose at 3 g/day. A small placebo-controlled trial in 18 men running 14 km reported lower oxidative-stress markers and higher glutathione with MSM.
Mucolytic activity (allergic rhinitis context)
MSM may have mild mucolytic effects, reducing mucus viscosity. Possible mechanism for upper respiratory symptom relief in seasonal allergic rhinitis. Not as well-characterized as anti-inflammatory mechanism.
Possible mast cell stabilization
Proposed mechanism for the allergy-symptom reports: MSM might stabilize mast cells and reduce histamine release. In the open-label allergy study, plasma IgE and histamine did not change (histamine was measured in only 5 people), so this remains hypothetical.
Clinical trials
Evidence review and pooled analysis of MSM and DMSO for osteoarthritis pain.
326 patients with osteoarthritis in 3 randomized trials (2 DMSO, 1 MSM)
3 high-quality clinical trials (2 DMSO, 1 MSM, total N=326). Pooled VAS pain reduction 6.34 mm (95% CI -0.49 to 13.17), neither statistically nor clinically significant. Only one trial tested MSM. The authors said evidence suggests DMSO and MSM are not clinically effective for OA pain, but no definitive conclusions can be drawn given mixed findings and inadequate dosing periods.
Randomized, double-blind, placebo-controlled trial in 118 patients with mild-moderate knee OA.
118 patients with mild-moderate knee OA
Four arms: glucosamine 500 mg, MSM 500 mg, the combination, or placebo, three times daily for 12 weeks. All three active arms improved symptoms versus placebo. The combination gave the largest drops in pain and swelling indices, acted faster than glucosamine alone, and was the only arm reported to significantly lower the Lequesne index (WOMAC was not used). Its 1.5 g/day MSM dose was lower than in the other MSM knee OA trials cited here (about 3.4 to 6 g/day).
Multicenter open-label trial in 50 subjects with SAR. MSM 2,600 mg/day for 30 days.
50 subjects with SAR
Multicenter open-label trial in 50 subjects with SAR. MSM 2,600 mg/day for 30 days. Significant reductions in upper respiratory symptoms by day 7 (p<0.01). Lower respiratory symptoms also improved by week 3. Effects sustained throughout 30-day trial. Open-label design limits causal inference but signal substantial enough to motivate randomized follow-up.
Randomized double-blind exploratory study with standardized allergen challenge methodology.
Healthy participants with a history of allergic nasal congestion
Every participant took MSM (an acute 12 g dose, then a randomly assigned 1, 3, or 6 g/day for 14 days) with no placebo group; nasal responses to an allergen challenge were compared with each person's own baseline. Daily doses cut nasal symptom scores by 53.72% and raised peak nasal inspiratory flow by 17.32%, most at 3 g/day. It adds blinding and dose randomization to the 2002 open-label trial, but without a placebo arm the findings are preliminary.
Double-blind, placebo-controlled trial of a topical silymarin plus MSM cream in 46 patients with stage I-III rosacea for 1 month.
46 patients with stage I-III rosacea
Double-blind, placebo-controlled trial of a topical silymarin plus MSM cream in 46 patients with stage I-III rosacea for 1 month. Redness, papules, itching, hydration, and skin color improved significantly. Because this is a topical two-ingredient product, it does not show what MSM alone or oral MSM does for skin.