Collagen is most commonly found in the skin, bones and connective tissue within the body, providing structural support, strength and a degree of elasticity (in combination with elastin). Collagen is also required in the replacement and restoration of dead skin cells. Some collagens also function as protective coverings for delicate organs in the body such as the kidneys. Collagen production naturally declines with age, reducing the structural integrity of the skin and leading to sagging skin, the formation of lines and wrinkles and the weakening of cartilage in joints. While young, the body consistently produces collagen, but collagen synthesis begins to decline around the age of 40, with a dramatic reduction in synthesis in women after menopause. By the age of 60 there is typically a considerable decline in collagen production. Learn more about collagen.