Any condition of reduced protein intake, and therefore of amino acids, is detrimental to the integrity of skin. However, there are many conditions in which a normal diet is not sufficient to cover the specific requirements of protein synthesis: from intense physical exercise to chronic illness (renal or cardiac insufficiency or chronic obstructive bronchitis), amino acids requirements increase enormously, because part is consumed to repair energy debts and only what remains can be used for the synthesis of new and more efficient proteins. Also ageing increases amino acids requirements. The passing of the years not only reduces the efficiency with which dietary proteins are absorbed, but also adds up to an energy deficit related to the loss of mitochondria in the cells. Mitochondria are the small organs (organelles) in every cell that make us efficient in producing energy, and producing energy is essential for the activities and functions of cells, and thus for their survival. For example, synthesising proteins has an extremely high energy cost.

Another important moment of our life, adolescence, characterized by rapid growth, requires a lot of amino acids to adapt the growth of new skin to that of the skeleton and internal organs: stretch marks are a typical example of inadequate systems of protein synthesis and difficulty on the part of cells that produce collagen, to do everything necessary even under the stimulus of various hormones.

Another difficult moment for the integrity of skin is when it is exposed to sunlight: the synthetic needs increase in proportion to the intensity and duration of exposure to ultraviolet and infrared In this case, the activation of collagenases(the enzymes of the dermis that destroy aged or damaged collagen) is very high, and fibroblasts need amino acids to make energy and synthesis in enormous quantities, and in particular during the night, when repair is more intense and not inhibited by pro-inflammatory solar radiations.