Collagen supplementation has been found to decrease pain and improve stiffness in osteoarthritis (1). Collagen supplementation may also help to keep connective tissues in tendons and ligaments strong in active people who frequently use them. This is great news for athletes prone to injury in agility sports or running etc. Collagen may also increase recovery of connective tissues following injury.
There is some evidence that collagen supplementation increases skin elasticity and promotes skin hydration (2). This could lead to an improved appearance in lines and wrinkles. However, most of the research currently showing favourable results for collagen supplements has been paid for by the collagen supplement industry, using poor study designs. Therefore we are in need of some more scientifically robust and less biased research for definitive answers.
There is some evidence that collagen supplementation can improve bone mineral density, meaning the thickness and strength of the bone, in post menapausal women (3). This is significant as bone density becomes increasingly difficult to maintain for aging women and can have huge health implications.