MSM, methyl sulfonyl methane, 99.9% pure Methyl Sulfonyl Methane (MSM) (99.5%) Vegan Source Reported Benefits of MSM supplementation: A bio-available form of organic sulfur that builds tissue throughout the body Improves mucosal surfaces in the respiratory tract therefore helps to maintain lung tissue integrity Improves structure of joint lubricating fluids to decrease pain associated with degenerative joint disease.