- Carotenoids: contained in green and yellow vegetables
- Retinol esters: contained in foods of animal origin
All retinol esters are fat-soluble provitamins bound to other fats, therefore, during digestion they require "pancreatic enzymatic hydrolysis (lipase and carboxyl ester-lipase), and intestinal hydrolysis (retinyl-ester hydrolase present on the enterocyte membrane). L" absorption of retinol occurs by facilitated diffusion and depends above all on the quantity of provitamin ingested, on the lipid composition of the meal and on the concentration of bile acids poured into the intestinal lumen; there conversion of provitamin into vitamin A occurs in the intestinal lumentherefore, in the lymphatic circulation (the first way of transporting lipids) it is already available in the form of an active molecule. Retinol performs very important functions in maintaining visual integrity and cell differentiation.
at the metabolic level, more precisely in the skin. The chemical process involved is photo-dependent, that is, it can occur ONLY after sun exposure to ultraviolet (UV) rays. If the diet is deficient in provitamins or the sun exposure is insufficient, disturbances in calcium metabolism and skeletal ossification may occur.
, is the inactive molecule of the vitamin pantothenic acid; panthenol is widespread among foods and ensuring its supply with the diet is not a common problem. Being a precursor of pantothenic acid, provitamin B5 is essential for the constitution of coenzyme A, an essential component in the metabolism of carbohydrates, amino acids, fatty acids and steroid compounds. Panthenol is also commonly defined as the "beauty vitamin". thanks to the action favoring the maintenance of skin tone, elasticity and hydration, as well as in the repair of damaged hair.extremely important, without which the risk of hypovitaminosis would significantly increase.
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