Vitamin A

Vitamin A, depending on its chemical structure, is called retinol, retinal, or retinoid.

Vitamin A is found in animal-derived foods – fish oils, butter, egg yolk, cod liver, beef liver, milk, cream, and cheese.

Beta-carotene is mostly found in carrots, pumpkins, tomatoes, cabbages, spinach, broccoli, and other green vegetables, as well as apricots.

Since vitamin A is absorbed with fats, it is advisable to consume carrots or their juice with a little oil or fat.

Skin. Vitamin A is essential for cell growth and multiplication. It ensures the normal condition of epithelial tissues (skin and mucous membranes). A deficiency in vitamin A causes the skin and mucous membranes to dry out, leading to cracks in the skin and a significant decrease in resistance to infections.

Vision. Absorbed vitamin A or carotenoids are converted into retinol in tissues, which is then converted into retinal or retinoic acid. Retinal is important for vision function, while retinoic acid is needed for intracellular retinoic acid receptors.

Vitamin A is used for rhodopsin synthesis in response to any light stimulus. This is especially important for people who spend a lot of time in front of televisions or computer screens, where their eyes need to react to contrasting light stimuli almost every second, resulting in a high demand for vitamin A. Over millions of years, the eye has developed a dense network of blood vessels to ensure the supply of vitamin A. With each light stimulus, there is a chemical breakdown of rhodopsin molecules. Simultaneously, during biosynthesis, new rhodopsin molecules are formed from proteins and vitamin A. If there is a deficiency of vitamin A, vision inevitably begins to deteriorate. Furthermore, a lack of vitamin A causes the cells of the cornea to dry and harden, leading to the loss of the eye's protective tear film. Consequently, tear ducts become blocked, the conjunctiva (eyelid lining) dries out, increasing the risk of developing conjunctivitis.

Both vitamin deficiency and overdose can be very harmful or even fatal. A deficiency impairs night vision, causes the skin to become pale and dry. Vitamin A deficiency can result from unhealthy, inadequate nutrition, or impaired intestinal absorption.

Symptoms: digestive disorders, nausea, vomiting, vision problems, dizziness, uncoordinated movements. Severe overdose causes joint and bone pain, liver enlargement. The lethal dose varies among different animals – some animals (especially those adapted to polar conditions) can accumulate vitamin doses in their liver that are lethal to humans.