L-Proline is an amino acid that is essential for the synthesis of collagen, the most abundant protein in mammals. Collagen is the main structural protein that constitutes all human connective tissues, including skin, tendons, ligaments, joints, bone, and vasculature (veins and arteries). L-Proline therefore provides building blocks that help to stabilize and strengthen the structural components of the body. Although proline can be made in the body, low protein and vegetarian diets may not provide optimal support for the production of collagen. NOW L-Proline is 100% vegetarian. Our NOW natural and organic Supplements are an effective way to ensure you and your loved ones are getting essential vitamins, minerals and nutrients for daily optimal health. Since 1968, NOW has been making top quality products that are tested to the highest standards to empower people to lead healthier lives. Our promise - what is on the label, is precisely what is in the bottle.