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.