Health, resilience and youthful appearance of the skin depends, among other things, on several key classes of biological molecules, just like the quality of a house depends on the quality of bricks, beams and concrete. The most important skin molecules are collagen, elastin, glycosoaminoglycans and proteoglycans.

Collagen is a protein forming the structural grid that holds other skin structures. It plays a role somewhat similar to that of steel rods in a reinforced concrete block. It gives the skin its strength and durability. As any other protein, collagen is composed of amino acids. However, it is unusually rich in a few specific amino acids, proline, hydroxyproline, lysine and glycine. Some experts believe that foods or supplements rich in these amino acids may benefit the skin by stimulating collagen production. There is a number of other ways to stimulate collagen production, including topical vitamin C and copper peptides. Increasing collagen production is important because age-related decline in the collagen synthesis is partly responsible for the signs of skin aging such as thinning, wrinkles and sagging.

Elastin is also a protein. It is more stretchable than collagen and helps maintain skin resilience and elasticity. Elastin contains two special amino acids, desmosine and isodesmonsine. When both elastin and collagen and abundant and undamaged, the skin easily regains its shape after being stretched or folded. Just as collagen, elastin deteriorates with age, leading to wrinkles and facial sag.

Glycosoaminoglycans (GAGs) and proteoglycans are special biological polymers whose key role is to hold moisture in the skin. In essense, they are extremely effective natural moisturizers - far more effective that common cosmetic moisturizers. Hydrated GAGs and proteoglycans help the skin stay plump and fresh and provide mechanical support for skin cells. GAGs are composed of special units (mainly water-holding sugars) such as glucosamine hydrochloride, N-acetyl glucosamine, and glucosamine sulfate. These units combine to form various types of GAGs, such as hyaluronic acid, keratin sulfate, heparin, heparin sulfate, dermatin sulfate, and chondroitin sulfate. Proteoglycans are larger than GAGs and are formed when certain types of GAGs are attached to a protein backbone. Since GAGs and proteoglycans are composed largely of water-holding sugars, supplementing one's diet with these sugars may enhance the skins production of GAGs and proteoglycans. In particular, N-acetyl-D-glucosamine, D-glucosamine hydrochloride, and D-glucosamine sulfate are often used as supplemets to increase skin moisture.