Methylsulfonylmethane, which is often abbreviated to MSM, is a sulfurous substance that is found naturally in your body. MSM is sold as nutritional supplements for a variety of health-promoting purposes. As with any nutritional supplement you should talk to your health care practitioner before supplementing with MSM.SM and Inflammatory Disorders. Alternative medical practitioners suggest that MSM supplements help treat chronic pain and a variety of inflammatory disorders, including rheumatoid arthritis, osteoporosis, bursitis, tenosynovitis, tendinitis and eye inflammation.