Vitamin A, alternatively referred to as retinol, beta-carotene, axeroftol, and pro-vitamin A

Vitamin A exerts a significant impact on vision as it is a component of rhodopsin, the photosensitive pigment of the retina of the eye that enables sight in low light conditions. Without this vitamin, metabolism of proteins and steroid hormones would be impossible. It is involved in the proper functioning of cell growth processes and in the differentiation of body cells, particularly epithelial cells and bone tissue. Vitamin A is also essential for maintaining the health of bones and teeth. It has a very broad range of action and is an effective remedy against pigment spots, scars, small wounds, and bruises. Furthermore, it has been proven to prevent wrinkles, which is why it can be found in anti-wrinkle cosmetics. The human body can store large amounts of Vitamin A but can also lose it quickly. Vitamin A is fat-soluble, hence it is crucial to consume it in combination with different kinds of fats. It aids in maintaining an attractive appearance and can also help in combating acne and hair loss. It possesses antioxidant properties and protects cells from the harmful effects of free radicals. It also supports the immune system. However, it is important to note that studies show that high doses of synthetic β-carotene in both smokers and laboratory animals exposed to cigarette smoke cause an increased frequency of lung cancer. Therefore, if a product label states that it contains Vitamin A, it is usually either synthetic or occurs in the form of a provitamin, which can be converted into Vitamin A.

Many people believe that carrots are a good source of vitamin A, which is not true. In reality, carrots contain beta-carotene, also known as provitamin A, which the body must convert into vitamin A. Unfortunately, beta-carotene is only absorbed in 20-50% and not converted in a 1:1 ratio, but rather approximately 1:6 to 1:48. Vitamin A deficiency can occur in people with diabetes and those with problems related to thyroid function. Individuals who have had their gallbladder removed may also have problems with a deficiency in vitamin A. Deficiency can also occur during prolonged periods of fasting or with long-term consumption of a low-fat or fat-free diet. Symptoms of vitamin A deficiency may also occur with a zinc deficiency, which is essential for the transportation of vitamin A in the body. Symptoms of vitamin A deficiency include brittle and fragile nails, dry and brittle hair, dry and rough skin, skin rashes, decreased appetite, fatigue, increased susceptibility to infections, and visual disturbances. In the case of visual disturbances, it is worth noting that a lack of vitamin A can lead to degeneration of the tear glands, which manifests as insufficient tear production and dryness of the cornea. This can ultimately lead to blindness. Diabetics, whose wounds heal slower, should remember that a deficiency in vitamin A can lead to slower wound healing. It can also lead to fertility disorders and an increased risk of oral, throat, and lung cancer in smokers.

It is worth noting that an excess of vitamin A can induce hypervitaminosis. This can present as irritations and gastrointestinal disturbances such as vomiting, lack of appetite, or nausea. It can also lead to skin discoloration and dangerous enlargement of the liver and spleen. Furthermore, an excessive quantity of vitamin A can cause hair loss, itchiness, and dry skin.

Vitamin A and provitamin A can be found in a wide range of food products, including: pork liver, sea fish and oil derived from them, chicken eggs, particularly the yolk, fatty cheese varieties such as subcutaneous and brown cheese, carrots, lettuce, spinach, pumpkin, chicory, parsley leaves, cereal grains, broccoli, tomatoes, corn, porridge, and raspberries. It is important to note that vitamin A should be consumed with fats, as it is fat-soluble. In countries where rice is the main component of the diet, vitamin A is supplied to the body in small amounts, which can lead to deficiencies. Therefore, a special type of rice, known as 'golden rice', has been developed which contains genes from corn that encode provitamin A, in order to increase its availability. Finally, the general guidelines for vitamin A consumption are presented.