Collagen is a protein that's mainly found in skin, hair, nails, and other connective tissues in the body, making it the most abundant protein in humans. It's slightly different to whey and casein protein because it has a high level of the amino acids, glycine, proline, hydroxyproline and arginine.
As we age, collagen production naturally declines by around 1.5% every year, leading to weakened muscles and joints, as well as visible signs of ageing like sagging skin, wrinkles and thinner hair.