Vitamin A Deficiency: Most Effective Supplements

Vitamin A, also known as retinol, is a fat-soluble vitamin essential for numerous biological functions. Discovered in 1913, it was the first vitamin identified, which is why it was assigned the first letter of the alphabet. Vitamin A exists in different forms in the body, such as retinol (vision), retinal (retina), retinoic acid (bones and mucous membranes), and retinyl palmitate (storage in the liver). It is essential for vision, particularly the eye's adaptation to darkness, as well as for cell growth, reproduction, and regulation of the immune system.

Essential Role of Vitamin A

Vitamin A plays a central role in cell growth and differentiation, as well as in the transcription of certain genes and the synthesis of specific proteins. It also contributes to the formation of teeth, bones, and skin, and to the maintenance of the mucous membranes of the eyes, respiratory and urinary tracts, and intestines, which constitute the first line of defense against infections. Additionally, it promotes iron absorption and participates in the regulation of inflammatory responses due to its antioxidant action.

Dietary Sources of Vitamin A

The body can obtain vitamin A directly from animal-derived foods such as liver, eggs, and dairy products. It can also convert certain carotenoids found in plants, like carrots and spinach, into vitamin A. Carotenoids, with beta-carotene being the most well-known, are considered provitamins A because they can be converted into vitamin A by the body. The main dietary sources also include cod liver oil, green leafy vegetables, and certain fruits like apricots and melons.

Vitamin A Deficiency: Causes and Consequences

A deficiency in vitamin A, although rare in developed countries, can lead to severe consequences. In parts of the world where nutritional intake is insufficient, vitamin A deficiency is a major cause of childhood blindness and mortality. This deficiency can be primary, due to insufficient diet, or secondary, resulting from disorders affecting the absorption, storage, or transport of vitamin A. Symptoms include vision impairment, particularly night blindness, dry eyes, dry skin and brittle hair, as well as decreased immune function, increasing the risk of repeated infections. In developed countries, deficiency is generally seen in individuals with conditions that compromise fat absorption, such as cystic fibrosis, Crohn's disease, or in those suffering from chronic intestinal malabsorption. In children, severe deficiency can cause growth delays and serious complications, including vision reduction that can lead to blindness if untreated.

Recommendations and Precautions

To prevent a vitamin A deficiency, it is advised to regularly consume foods rich in retinol and beta-carotene. Sufficient protein and zinc intake is also essential for vitamin A metabolism, while vitamin E can enhance its absorption and storage. It is important to note that an excess of vitamin A can cause toxicity, particularly at the liver level. Pregnant women should exercise caution, as excess vitamin A can be dangerous for fetal development. In contrast, beta-carotene does not present the same risks, since the body only converts the necessary amount into vitamin A, thereby avoiding excessive storage. To ensure adequate vitamin A intake, it is recommended to consume about 0.8 mg per day for an adult, according to European guidelines.