At a glance
Vitamin A is a fat-soluble vitamin and a collective term for the retinoids related to retinol.
In Vykea: retinyl ester (600 µg per sachet)
Preformed vitamin A in high doses is risky during pregnancy.

Vitamin A is a fat-soluble vitamin. The term does not refer to a single substance but to a group of related compounds known collectively as retinoids. These include retinol, its aldehyde retinal, and retinoic acid. In addition, the body can form vitamin A from certain carotenoids in plant foods, above all beta-carotene; these precursors are referred to as provitamin A. Vitamin A is important above all for vision, for skin and mucous membranes, for the immune system, iron metabolism and the control of cell specialisation. In Omnia All-In-One we use vitamin A as a retinyl ester, at 600 µg per sachet. This entry explains the forms, food sources, functions, requirements, laboratory testing, possible signs of deficiency and interactions of vitamin A.

Vitamin A occurs in several forms that differ in origin and utilisation. In animal foods, it is present mainly as preformed vitamin A, usually as retinyl esters (for example retinyl palmitate or retinyl acetate). These esters are broken down in the gut and absorbed as retinol. In the body, retinol can be converted as needed into retinal, which is required for vision, and into retinoic acid, which is involved in gene regulation.

Plant foods do not contain vitamin A directly, but in the form of provitamin A carotenoids, above all beta-carotene. The body converts these precursors into vitamin A depending on its vitamin A status. This conversion is limited and varies from person to person, which is why plant sources yield less in terms of quantity than animal sources. For comparability, the different forms are expressed in retinol activity equivalents (RAE). 1 µg RAE corresponds to one microgram of retinol, 12 µg of beta-carotene and 24 µg of other provitamin A carotenoids.

Because vitamin A is fat-soluble, it is absorbed in the gut together with dietary fats. A very low-fat diet and a deficiency of zinc or iron can impair its utilisation. Omnia uses vitamin A as a retinyl ester.

Preformed vitamin A (retinol and its esters) is found mainly in animal foods. Liver is particularly rich in it, and cod liver oil, egg yolk, butter, cheese and some fish also contribute. Provitamin A carotenoids such as beta-carotene are found mainly in brightly coloured vegetables and fruit: in carrots, sweet potatoes, pumpkin, apricots, mango and papaya, as well as in dark green leafy vegetables such as spinach and kale.

Carotenoids are better absorbed from vegetables that have been cooked and prepared with a little fat than from raw vegetables. Vitamin A and its precursors are sensitive to light and oxygen, which is why losses can occur during long storage. Regular alcohol consumption can also impair vitamin A status.

Through its various forms, vitamin A is involved in several fundamental processes:

The next section shows which of these functions are authorised as health claims.

The following health claims are authorised for vitamin A in the EU:

These claims apply to vitamin A in general and therefore also to the retinyl ester form used in Omnia.

The following values are given in retinol activity equivalents (RAE) and are taken from the D-A-CH reference values of the German Nutrition Society (DGE), which were updated for vitamin A in 2020. You will find an explanation of RAE above in the section on the forms. The values for infants are estimated values; the other figures are recommended intakes.

The nutrient reference value for labelling (NRV) is 800 µg per day. For adults, including women of childbearing age and pregnant and breastfeeding women, the European Food Safety Authority (EFSA) gives a tolerable upper intake level of 3,000 µg per day for preformed vitamin A, i.e. for retinol and retinyl esters. EFSA confirmed this upper limit in its updated assessment of 2024. It applies only to preformed vitamin A. No corresponding upper limit has been set for provitamin A carotenoids such as beta-carotene, as their conversion in the body is regulated.

In some life stages and situations, vitamin A requirements are higher or the risk of inadequate supply is greater: during growth phases, while breastfeeding, when fat absorption or absorption from the gut is impaired (for example with chronic inflammatory bowel disease, after bowel surgery or with pancreatic insufficiency), with certain liver and biliary diseases, with zinc deficiency and with regular alcohol consumption. A purely plant-based diet covers requirements exclusively through provitamin A carotenoids, whose conversion is limited, so care should be taken to ensure an adequate intake of carotene-rich foods.

In Germany, the vitamin A status of the general population is considered adequate on average. Worldwide, by contrast, vitamin A deficiency is one of the major nutrition-related health problems in some regions, especially among children.

Vitamin A is necessary for normal embryonic development, but at the same time a very high intake of preformed vitamin A during pregnancy is risky. In high doses, retinol is harmful to the foetus (teratogenic) and is associated with malformations in the unborn child. For this reason, EFSA based the tolerable upper intake level of 3,000 µg per day for preformed vitamin A specifically on protection against such malformations.

Pregnant women and women who could become pregnant are therefore advised to avoid meals containing a lot of liver and high-dose vitamin A supplements. This advice concerns preformed vitamin A (retinol and retinyl esters). This upper limit does not apply to beta-carotene as provitamin A.

Note: Whether vitamin A intake during pregnancy is advisable, and at what level, should be clarified and supervised by a doctor.

Vitamin A status is determined by a doctor from a blood sample. The usual method is to measure retinol in serum or plasma, which should be done after fasting and with the sample protected from light. However, the serum value is of limited informative value, because by far the largest part of vitamin A is stored in the liver and the blood level is kept constant over a wide range. A markedly low serum retinol level therefore only indicates a deficiency that is already advanced.

In addition, retinol-binding protein (RBP), which transports vitamin A in the blood, can be measured. The ratio of retinol to RBP allows further conclusions to be drawn about vitamin A status.

Note: Interpreting the measured values and any supplementation should be left to a doctor.

Vitamin A deficiency usually develops slowly, as the body has stores in the liver. An early and typical sign concerns vision: the eyes may be less able to adapt to darkness, a condition known as night blindness. With pronounced and longer-lasting deficiency, the mucous membranes of the eye can dry out (xerophthalmia), leading in severe cases to serious damage to the cornea.

Other possible signs are dry, scaly skin, changes in the mucous membranes and increased susceptibility to infections, because the barrier function of the mucous membranes and the body's defences may be weakened. In children, persistent deficiency can impair growth and development.

Such signs are not conclusive and can have many causes.

Note: Investigation and diagnosis should be left to a doctor.

Some active ingredients and other substances can affect vitamin A metabolism. During treatment with orally taken retinoids (for example isotretinoin), which are related to vitamin A, additional vitamin A intake should be avoided, as the effects add up and the risk of overdose increases. Certain lipid-lowering medicines and some laxatives can reduce the absorption of vitamin A. Regular alcohol consumption also impairs absorption and storage.

Note: If you take such active ingredients, you should check with a doctor before taking additional vitamin A.

In metabolism, vitamin A is linked to other nutrients: vitamin A is involved in iron metabolism, and zinc is needed for vitamin A metabolism (more on this in the section on the interplay with zinc below). Because vitamin A is fat-soluble, taking it with a meal containing fat supports absorption.

Vitamin A can enter the body by two routes: as preformed vitamin A (retinol and retinyl esters) from animal foods and as provitamin A in the form of carotenoids, above all beta-carotene, from plant foods. In the body, beta-carotene is converted into vitamin A according to need. This regulation is the reason why no tolerable upper intake level has been set for beta-carotene in the same sense as for preformed vitamin A. However, smokers are advised to exercise caution with very high doses of beta-carotene from isolated supplements. In Omnia, vitamin A is present as a retinyl ester, i.e. as preformed vitamin A.

Vitamin A and zinc interlock closely in metabolism. Zinc is needed for vitamin A metabolism and is involved at two key points. Firstly, it is involved in the formation of retinol-binding protein, the transport protein that delivers vitamin A from the liver to the tissues. Secondly, zinc is involved in the turnover of vitamin A in the visual cycle, as the conversion of retinol into retinal, which is needed for vision, takes place via a zinc-dependent enzyme (a retinol dehydrogenase).

It follows from this interplay that zinc deficiency can impair vitamin A metabolism. Reviews describe that inadequate zinc status can be accompanied by reduced retinol levels in the blood, which is attributed, among other things, to reduced formation of retinol-binding protein in the liver. Cell-based studies support this relationship and show that the availability of zinc influences the formation of retinol-binding protein in liver cells. These are general relationships from nutritional science, not a promise of effect for any individual product.

You can find more about the partner nutrient in the Zinc entry.

Vitamin A is contained in Omnia All-In-One:

The amount stated is given in retinol activity equivalents (RAE). The % of NRV is based on the labelling value of 800 µg. Because vitamin A is fat-soluble, we recommend taking it with a meal to support absorption. The amount stated is well below the tolerable upper intake level of 3,000 µg per day for preformed vitamin A given by EFSA for adults; however, if you use several supplements at the same time, always take your total intake into account. One daily dose corresponds to one sachet.

Food supplements are not a substitute for a balanced, varied diet and a healthy lifestyle.

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