Diet and skin aging : biochemical aspects

Skin aging is a complex biological process, generally separate in chronological aging and photo-aging, and is influenced by internal and external factors, particularly the cumulative damage resulting from exposure to ultraviolet (UV) radiation. The combined effects of these two processes affect changes in the dermal matrix typical of aging and their main clinical signs: wrinkle formation, laxity, fragility, and irregular pigmentation of aged skin. Histologically, collagen decreases, and the dermis is replaced by abnormal elastic fibres that reduce the elasticity of the skin leading to wrinkle formation. Numerous studies have been conducted to clarify the molecular mechanisms underlying these processes and the role played by nutrition on them, by using models that include cellular aging, oxidative stress, high-frequency chromosomal abnormalities, monogenic mutations, and chronic inflammation. Mainly UV radiation induces the formation of reactive oxygen species and DNA damage, leading to increased production of matrix metalloproteases that induce the degradation of the extracellular matrix and decreased production of collagen in keratinocytes and fibroblasts. Several nutrients with anti-oxidant and anti-inflammatory properties (vitamins, carotenoids, plant-based polyphenols, etc.) have been widely used in skin care as either topical agents or oral supplements in an attempt to prolong the youthful appearance of the skin. However, although many studies have shown that an imbalance in nutrition and uncorrected eating habits are important causes of skin aging, the effectiveness of these treatments has yet to be fully demonstrated. During the report, the possible molecular mechanisms of skin aging will be discussed and advances in research regarding the possible effects of diet and dietary supplementation on these mechanisms will be summarized.