This nutrient brings light into the darkness

What is vitamin A?

Vitamin A is an essential fat‑soluble nutrient made up of several chemically distinct compounds that together exert characteristic biological effects in the body. The physiologically most important form is retinol, which is stored in the body and can be converted, as needed, into other active forms such as retinal or retinoic acid. Retinol is stored as retinyl esters, which are found only in animal foods.

In addition to this so‑called preformed vitamin A, there are plant precursors known as provitamin A carotenoids. The best known is β‑carotene, which the body can convert into active vitamin A. However, this conversion varies greatly between individuals and depends on factors such as genetics, health status and fat intake. Especially in vegetarian or vegan diets, these carotenoids play an important role in ensuring adequate vitamin A supply.

What does the body need vitamin A for?

Vitamin A fulfils many vital functions in the body. One of its most important roles is in low‑light vision: as retinal it is part of the visual pigment in the retina responsible for light‑dark perception. Vitamin A also supports the immune system by strengthening the barrier function of the skin and mucous membranes and by influencing the development of immune cells – an important foundation for defence against pathogens.

Vitamin A is indispensable for cell division and tissue maturation. It helps cells to specialise and remain functional, particularly in skin, mucous membranes, bone and teeth. In the skin, retinol is converted to retinoic acid, which contributes to renewal of skin structure and is valued for its regenerative effects in cosmetic preparations.

Vitamin A also plays a significant role in reproduction: it influences the production of sex hormones and is involved in sperm development as well as processes related to pregnancy and embryonic development. The provitamin form, beta‑carotene, additionally acts as an antioxidant and helps neutralise cell‑damaging free radicals.

Furthermore, vitamin A supports iron metabolism by promoting the formation of red blood cells, regulating the availability of iron stores and contributing to the fight against infection‑related anaemia. In this way it contributes at multiple levels to the overall health and performance of the organism.

What causes vitamin A deficiency?

Vitamin A deficiency can have several causes. In many cases it stems from a chronically unbalanced diet that contains only small amounts of vitamin A‑rich foods or their precursors. Deficiencies are especially common in regions where people rely mainly on nutrient‑poor staple foods such as white rice or maize and lack fatty or vitamin‑rich products.

Even with adequate dietary intake, a deficit can occur if the body cannot absorb or utilise the vitamin properly. This particularly affects people with gastrointestinal conditions such as chronic inflammatory bowel disease, coeliac disease or cystic fibrosis. Such disorders impair absorption of fat‑soluble vitamins in the small intestine.

A deficit can also arise after surgery, for example following gastric bypass or bowel resection, when significant portions of the digestive tract are bypassed. Other risk factors include liver or pancreatic disease, as these organs play central roles in storage and utilisation of vitamin A and in fat digestion. If their function is impaired, vitamin A availability can be substantially reduced.

How does vitamin A deficiency present?

Vitamin A deficiency can manifest in many ways because this nutrient is central to numerous bodily functions. The most noticeable signs concern vision: it often begins with difficulties seeing at dusk (night blindness). Foamy deposits on the conjunctiva (Bitot’s spots) or marked dryness of the eyes may also occur. In severe cases, blindness can result. The skin is affected too: it often becomes rough, dry and scaly or shows increased keratinisation. Hair loss may also be increased.

Deficiency also affects the mucous membranes, which dry out when supply is inadequate and become more susceptible to infection. The risk of respiratory infections, mouth and gum inflammation or genital fungal infections increases. Smell and taste can also be impaired. Many affected people suffer from general fatigue, concentration problems and an increased risk of infections owing to a weakened immune system.

Fertility may also be impaired: in men sperm production can decrease, and in women cycle disturbances or changes in the genital mucosa may occur. During pregnancy, vitamin A deficiency carries a risk of birth defects in the unborn child. Children who are undernourished often show growth retardation or dental development problems. A deficit can also negatively affect iron metabolism and lead to anaemia.

Severe deficiency can cause changes to bone or cartilage, for example uncontrolled bone growth in inappropriate places. Symptoms are varied and not always clear. A reliable diagnosis can only be made by a medical examination.

Can you overdose on vitamin A?

Yes, an overdose of vitamin A is possible, particularly with high‑dose supplements or consumption of large amounts of certain animal products such as liver. This is especially critical with synthetic retinol or isolated beta‑carotene, as high doses can pose health risks. Natural carotenoids from plant sources are generally safe, while artificially produced forms may increase the risk of serious adverse outcomes in certain groups, such as smokers or cardiovascular patients.

Acute poisoning becomes apparent quickly with symptoms such as nausea, dizziness or visual disturbances, while long‑term overconsumption may lead to skin changes, joint pain or liver problems. Pregnant women should be particularly cautious, as excess retinol can endanger fetal development. In general, anyone considering vitamin A supplements should discuss intake in advance with a healthcare professional.

How much vitamin A is needed per day?

Daily vitamin A requirements depend on age, sex and individual circumstances. On average, adult women need about 700 micrograms retinol equivalent per day, men about 850 micrograms. During pregnancy requirements rise to about 800 micrograms and during lactation to about 1'300 micrograms per day.

Beta‑carotene, the plant precursor of vitamin A, also plays an important role: a daily intake of about 2 milligrams is considered appropriate. Certain groups, such as smokers, people with chronic liver disease, rheumatic patients or persons exposed to heavy air pollution, may require higher intake.

For healthy adults, a regular intake of up to 3'000 µg retinol equivalent per day is considered safe. Supplements should nevertheless be used judiciously. Pregnant women in particular are advised to consult a physician before taking supplements.

How to meet your vitamin A needs: practical tips

• Include liver and liver pâté regularly, as they contain extremely high amounts of directly available vitamin A. Just 30 grams of calf liver pâté can exceed an adult's daily requirement.
• Add yellow and orange vegetables such as carrots, pumpkin and sweet potatoes to your meals. They are rich in beta‑carotene, which the body can convert to vitamin A. It is best to cook these vegetables lightly and add some fat.
• Also make a habit of eating vitamin A‑rich vegetables like kale, spinach or lamb's lettuce. They are an important plant source of beta‑carotene – especially in vegetarian or vegan diets.
• Combine raw vegetables such as bell pepper or lamb's lettuce with a fatty dressing to improve carotenoid absorption. Rapeseed or olive oil work well.
• Eggs are easy to include in everyday meals and the yolk is a good source of natural retinol. Eat them regularly, for example as a breakfast egg or in salads.
• Avoid prolonged heat exposure when preparing vitamin A‑rich foods, as both retinol and beta‑carotene are heat‑sensitive. Steaming is often better than boiling.
• Store sensitive foods such as kale or liver in a cool, dark, dry place to preserve vitamin A content, since light and oxygen promote its breakdown.
• If you eat fish, choose types such as eel, salmon or tuna as a source of animal vitamin A. Fatty species are particularly suitable.
• If you follow a vegetarian diet, include dairy products like camembert or butter, which contain usable vitamin A and are versatile, for example as a spread or in sauces.
• Avoid taking supplements with isolated vitamin A without medical advice, as overdose can be harmful. Overdosing via natural foods is unlikely.
• Cantaloupe melon, apricots or mangoes make good fruity additions to main meals or snacks to help cover provitamin A intake from fruit. Combining them with yoghurt or nuts helps increase fat intake.
• To prevent liver damage, headaches and vision disturbances, follow reference values for vitamin A to avoid hypervitaminosis.

Whether as retinol or beta‑carotene: vitamin A is crucial for a functioning immune system and good vision. A conscious choice of foods is therefore essential.