Vegan Gluten Free Ultra-Pure Crystalline Sulfur Dietary Supplement OptiMSM? The Sunfood Difference? MSM is a naturally occurring form of dietary sulfur found in fresh raw foods and rain water. Sulfur is a vital mineral that is needed by the body for normal structure and function. It makes up the protein and connective tissue that comprises our body mass assists enzymes in performing chemical reactions and may help improve resistance to toxic substances. MSM can aid in rebuilding connective tissue with elastic sulfur bonds. It may also help increase flexibility as well as support recovery time from sore muscles and athletic injuries. Our Opti-MSM? is made exclusively in the USA and is the highest quality MSM available.