MSM is a naturally-occurring compound that provides sulfur for many important physiological functions in the human body. MSM and related compounds provide nearly 85% of the sulfur found in all living organisms. Sulfur comprises approximately 0.25% of body weight and is present at significant amounts in nerve tissue, muscle tissue, skin, hair and bones. MSM is found in fresh fruits, vegetables, seafood and meats. MSM levels decline with age which means that supplementation becomes more important as you grow older.