There is not officially a collagen RDA, but it is believed by some people that the modern diet is deficient in collagen (or collagen amino acid precursors). Some people take collagen supplement with the objective to counteract the natural decline in production with age. Collagen is not only used in the skin, but also by the vascular system for structure and flexibility.

As for absorption, some peptides do survive the trip through the stomach. Collagen powder is a convenient way to get the amino acids in the correct proportions that can replace less convenient methods like bone broths. Protein powders do not have the correct ratio.