Vitamins are organic compounds required in small amounts for the body metabolism, for growth and general wellbeing. Since the body cannot synthesize them, they have to be taken with food. No food can provide all vitamins, which is why a varied diet is needed to ensure a complete intake of these micronutrients.
Advances in Dairy Products, First Edition.
Edited by Francesco Conto, Matteo A. Del Nobile, Michele Faccia, Angelo V. Zambrini, and Amalia Conte. © 2018 John Wiley & Sons Ltd. Published 2018 by John Wiley & Sons Ltd.
Depending on their solubility in water or fat, vitamins are classified as:
- • Fat-soluble vitamins (A, D, E and K)
- • Water-soluble vitamins (B group: Bi, B2, B6, B12; vitamin C, folic acid, biotin, pantothenic acid, and niacin)
Vitamin A (retinol)
Vitamin A is a superior alcohol found as retinol in foods from animal sources. In plant- derived foods it is present as provitamin A or as carotenoids (alpha, beta, and gamma), which our organism is able to transform into vitamin A. Beta-carotene is the most biologically active form.
This vitamin has different functions: It is essential for vision, especially at night and for cell differentiation; as a consequence it is necessary for the immune system growth, development and maintenance. It is also fundamental for the integrity of epithelial cells and of mucous membranes; moreover, it has a central role in the development of lymphocytes. Vitamin A deficiency implies the reduction in the lymphocytes capacity of destroying bacteria (Wintergerst, 2007); in young infants and children its lack has been associated with increased infectious morbidity, including respiratory infection and diarrhea (Mayo-Wilson, 2011).
Some observational studies in adults have investigated the association between vitamin A and cancer (Gonzalez, 2011), cardiovascular diseases (Fletcher, 2003) and age- related eye illnesses, including cataract, age-related maculopathy and glaucoma (Cumming, 2000). Over the last few years, an excess of vitamin A has been related to negative effects, such as a possible increase in the risk of hip fracture. (Ai Min Wu, 2014).