By di Fondazione Valter Longo Onlus
Vitamin A is indispensable for the human organism, in which it present in the form of retinol. In nature, it exists in two forms: carotenoids (of vegetable origin) and retinoids (of animal origin). It is a fat-soluble vitamin that accumulates in the liver and is absorbed by the intestine.
WHAT VITAMIN A IS USED FOR/ USES OF VITAMIN A
Essential for a healthy sight, vitamin A (in the form of retinol) together with its precursors (carotenoids) is one of the components of rhodopsin: a light-sensitive pigment, present on the retina in the rods (organelles capable of capturing light). Retinol, therefore, plays an indispensable role in the mechanism of sight, especially night vision. Furthermore, vitamin A is involved in the regulation of the process of cell growth and differentiation. This is why it is essential in the early years of development, as well as for the wellbeing of tissues and organs. It is good for the skin because, in addition to promoting cellular regeneration, it regulates membrane permeability and tissue elasticity. Moreover, it is essential for the teeth and bones. Scientific evidence demonstrates the anti-oxidant role of vitamin A as antitumor. Its anti-oxidant power also acts in strengthening the immune system, as well as protecting the cardiovascular system and constitutes an excellent barrier to possible pulmonary infections.
EXCESSIVE OR NON SUFFICENT DOSES OF VITAMIN A
The daily requirement ranges from 3 to 10 mg per day, depending on the time of development, age, gender and specific conditions. In infants 4.5%; in children and teenagers from 3 to 7 mg. In adult males, the recommended dose is 7 mg; while in adult females it is 6 mg, in pregnancy 7 mg and during breast feeding 10mg. Deficiency or excess of vitamin A during gestation can cause fetus malformation and subsequent growth and development difficulties in pediatric age including acquired blindness. The lack of vitamin A in the organism, in fact, leads to vision problems, which initially manifest themselves with difficulty in twilight vision, up to causing blindness in the most serious cases. Other symptoms linked to vitamin A deficiency are immune system dysfunctions and increased sensitivity to infection.
In case of excessive vitamin A intake, it can lead to intoxications, with the appearance of various symptoms. Migraines, loss of coordination, visual disturbances, nausea and vomiting, for severe toxicity. Muscle pain, fatigue, loss of appetite, anemia, headache, irritability, blurred vision, for chronic toxicity. Seeing as how it accumulates in the liver, if in excess it can also cause permanent damage to liver and spleen.
IN WHICH FOODS IS VITAMIN A FOUND
Vitamin A, in the form of retinol, is found in products of animal origin, such as liver, oily fish (herring, salmon, tuna, cod liver oil), milk, cheese, butter, yogurt and egg yolk. Among vegetables, however, vitamin A is found in the form of carotenoids (such as beta-carotene) in particular in yellow, orange, and red colored vegetables. Amongst vegetables, we find it in carrots, pumpkin, peppers, tomatoes and sweet potatoes. In colored fruit, however, vitamin A is found in apricots, peaches, loquat, melon, watermelon, cherries, berries, mango and papaya. Vitamin A is also found in green vegetables such as spinach, chicory, parsley, broccoli and spirulina seaweed, but also in savoy cabbage, cabbage, Brussels sprouts, zucchini, celery, garlic, beans and, in part, also in whole grains (in particular in the wheat germ). Among the dried fruit, we find vitamin A in pistachios. Soybean oil also has a good content of vitamin A. Vitamin A is sensitive to heat and light, it degrades during the cooking process, so it is recommended to take fresh and seasonal foods, as well as eating raw fruit and vegetables. Furthermore, being fat-soluble, it is recommended to dress the vegetables with raw extra virgin olive oil.
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