By di Fondazione Valter Longo Onlus
Vitamin A is fundamental for the well-being of human organism, in which it is 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 USEFUL FOR?
It is fundamental to a healthy eyesight. 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. For this reason, 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 lung 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 mg; in children and teenagers from 3 to 7 mg. In adult men, the recommended dose is 7 mg; while in adult women 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: 1) migraines, loss of coordination, visual disturbances, nausea and vomiting for severe toxicity; 2) muscle pain, fatigue, loss of appetite, anemia, headache, irritability, and blurred vision for chronic toxicity. Because it accumulates in the liver, if in excess it can also cause permanent damage to liver and spleen.
WHICH FOODS CONTATIN VITAMIN A
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, vitamin A is found in the form of carotenoids (such as beta-carotene) in particular in yellow, orange, and red vegetables. Amongst vegetables, we find it in carrots, pumpkin, peppers, tomatoes, and sweet potatoes. In fruit, vitamin A is found in apricots, peaches, melon, watermelon, cherries, berries, mango, and papaya. Vitamin A is also found in green vegetables such as spinach, chicory, parsley, broccoli, and spirulina seaweed, as well as 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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