Vitamin A: Need, effect & deficiency

Vitamin A is a fat-soluble substance that is found in two main forms:

• as retinol found in animal products and

• as provitamin A (beta-carotene), found in plant-based foods.

While retinol can be used directly by the body, provitamin A (beta-carotene) must first be converted into the active vitamin A form.

Vitamin A is particularly present in high concentrations in liver and products containing liver. Other animal foods such as eggs and some fish (e.g. eel) also contain significant amounts of the vitamin.

In plant-based foods, vitamin A is not directly present, but rather in the form of provitamins such as beta-carotene and alpha-carotene, which the body uses as vitamin precursors. Some of these provitamins are already converted into vitamin A in the small intestine (approx. 17%). The other part is further metabolised into vitamin A by the liver, lungs, kidney and muscle cells after absorption into the body. Key plant sources of provitamin A carotenoids include vegetables such as carrots, pumpkin, red peppers, lamb’s lettuce, spinach and kale. People who rarely consume vitamin A-rich animal foods (e.g. liver) in particular should use these plant-based sources of vitamin A. In this case, it is necessary that the meal also contains fat to allow the vitamin to be absorbed into the body. Animal foods usually provide enough fat, so extra fat is not required.

An adequate supply of vitamin A is also possible in a purely plant-based diet, provided there are no digestive problems or fat digestion disorders and there are also sufficient active conversion enzymes. Furthermore, an adequate thyroid function is also crucial for the efficient conversion of provitamin A carotenoids to vitamin A.

Vitamin A is involved in numerous metabolic processes. The best known function is probably its role in vision. It is a component of the visual pigment rhodopsin, which makes it possible to see in poor light. In addition, vitamin A supports the growth and differentiation of cells that are important for the renewal of the skin and mucous membranes. Our immune defence also benefits from strengthening the external body barriers. In addition, vitamin A supports the innate and acquired immune system by promoting the formation of white blood cells and thus helping to fight off infections. The fat-soluble vitamin also plays a role in maintaining the higher functions in the central nervous system. Adequate vitamin intake also promotes fertility. On the one hand, it contributes to the formation of the two sex hormones testosterone and oestrogen; on the other hand, it is also important for sperm production and quality as well as for egg cell, placental and embryonic development.

The daily need for vitamin A depends on age, gender and individual circumstances. The recommended daily dose for adults is:

• Men: 850 μg retinol equivalent (RE)

• Women: 700 μg RE

Pregnant and breastfeeding women have an increased need for vitamin A to support the healthy development of the child. Similarly, people with certain diseases that affect fat absorption may have a higher need.

Vitamin A plays a role in the desire to have children. It helps in the production of testosterone as well as in the development of sperm cells and the placenta. However, even during pregnancy, a sufficient vitamin A supply is particularly important, as it affects cell division and the normal development of the embryo.

However, caution should also be exercised: Excessive intake of vitamin A, especially in the form of retinol, can be harmful during pregnancy. Therefore, women in this phase should pay particular attention to a balanced intake of food and should only take vitamin A preparations after consultation with their doctor.

Vitamin A is equally important for children as it promotes growth and vision. Children between the first and fourth years of age require approximately 300 μg retinol equivalent (RE) per day, while older children and adolescents require between 350 and 950 μg RE, depending on age and gender.

Vitamin A deficiency is common in developing countries, but can also occur in developed countries if the diet is permanently one-sided or certain diseases impair vitamin absorption. Typical symptoms of vitamin A deficiency include night blindness, increased susceptibility to infection, dry skin and corneal changes in the eye. In children, a deficiency often manifests as growth disorders and an increased susceptibility to disease.

Supplementation may make sense for people who do not consume sufficient vitamin A through their diet or who have an increased need. There are various forms of food supplements, including vitamin A capsules, drops or multivitamins. It is important not to exceed the recommended dose.