Collagen peptides are small pieces of protein from animal collagen, which is a naturally occurring protein in humans and animals. Collagen is found in skin, cartilage, bone, and other areas of the body. Collagen peptides are made by breaking down whole collagen proteins into smaller pieces, which are more easily absorbed by the body. When taken by mouth, collagen peptides seem to build up in the skin and cartilage, which may help improve some skin and joint conditions. Collagen peptides are used for aging skin and osteoarthritis. They are also used for osteoporosis, brittle nails, muscle strength, and many other purposes, but there is no good scientific evidence to support most of these uses. Collagen supplementation may help address the body’s natural decline in collagen production as we age. Collagen peptides come in both pill and powdered forms and are typically made from bovine (beef) or porcine (pork) sources. Marine collagen supplements, made from fish skin or scales, are also available.