Doctor's Best Synergistic Glucosamine Msm Formula contains Glucosamine Sulfate and Methylsulfonylmethane (MSM, from OptiMSM) to help support joint health. Glucosamine Sulfate helps support joint mobility. MSM supplies bioavailable sulfur needed to support joint health in addition to beauty benefits for hair, skin, and nails. Vitamin C is an ideal addition, to boost the body's own ability to produce and effectively use collagen, a structural protein that is an important component of joints, tendons, and skin. Vitamin C works synergistically with collagen for overall health of body functions and skin health.