Introduction Methylsulfonylmethane (MSM), also known as dimethyl sulfone (DMSO 2 ) and methyl sulfone, is an organic sulfur-containing compound that occurs naturally in a variety of fruits, vegetables, grains, and animals including humans. A white, odorless, slightly bitter-tasting crystalline substance containing 34-percent elemental sulfur, MSM is a normal oxidative metabolite product of dime...