Everything you need to know about vitamin A

Vitamin A - also known as retinol - has caused a real hype in recent years, especially in skincare. However, the vitamin also has an effect on many other bodily processes.

What is vitamin A?

This is a collective term for fat-soluble compounds that fulfil important biological functions. It includes various forms such as retinol, retinal, retinoic acid and provitamins such as beta-carotene. The two main forms are retinol (the active form of the vitamin) and carotenoids (the vitamin A precursor, also known as a provitamin). The body converts these into retinol in order to utilise it. Retinol has an effect on vision, the immune system, cell growth, skin health and reproduction.

What is a provitamin?

A provitamin is a precursor of a vitamin that can be converted into the actual active form in the body.

A well-known example is beta-carotene, which functions as provitamin A. In the body, it is converted into vitamin A (retinol), making it an important source of this vitamin. When the organism needs retinol, it can convert the stored vitaminoid to cover the vitamin A requirement.

Provitamins are often found in natural foods and contribute to the vitamin supply. They are a kind of "stockpile" that can be converted into the corresponding active vitamin when needed.

What is vitamin A good for?

Retinol is responsible for a number of vital functions and has various effects:

Sight: Retinal, a natural form of vitamin A, plays a key role in maintaining good vision, especially in the eye's adaptation to different light conditions and the formation of visual pigments. Retinal is also known as retinaldehyde: retinal is one of the bioactive forms of the vitamin in the body and a component of the visual pigment, rhodopsin, found in the rods of the retina of the eye [1].

Immune system: Retinol is important for the normal function of the immune system and helps to support the barrier function of the skin and mucous membranes, which protect against infection [2].

Cell growth and development: It is crucial for cell growth, differentiation and development of tissues, including the formation and maintenance of healthy tissue [3].

Skin health: Retinol promotes skin health by supporting the regeneration of skin cells and promoting the formation of collagen [4].

Reproduction: It is important for normal reproductive function in both men and women, including the development of sperm and supporting embryonic development [5,6].

Antioxidant properties: Retinol acts as an antioxidant that can protect cells from oxidative stress by neutralising free radicals, which may also contribute to heart health [7].

A balanced vitamin A level is therefore essential for maintaining health and supporting various vital bodily functions.

What does vitamin A actually do to the face?

Retinol has various positive effects on the skin on the face:

Skin regeneration: Retinol and retinoic acid promote cell renewal. It can improve skin texture by removing dead skin cells and stimulating the production of new, healthy cells [4].

Reducing fine lines and wrinkles on the skin: Retinol is often used in anti-ageing products as it can help reduce fine lines and wrinkles. It can increase collagen production, resulting in firmer and more elastic skin. Using retinol can improve the texture of the skin by refining the appearance of pores and smoothing imperfections in the skin [4,8].

Treatment of acne: Retinoids, chemical compounds structurally related to retinol, can help treat acne by reducing the clogging of the skin's pores, reducing inflammation and inhibiting the growth of acne-causing bacteria [9].

Evening out pigmentation: Retinol can help reduce hyperpigmentation, such as sun spots or age spots on the skin, by regulating the production of melanin [10].

It is important to note that highly concentrated retinol products can sometimes cause skin irritation, especially on sensitive skin. Therefore, the use and concentration of retinol-containing products should be customised and carried out under the advice of a dermatologist.

We have summarised further information on vitamins for the skin for you in this article.

How does a vitamin A deficiency manifest itself?

A lack of retinol can manifest itself physically in various ways:

Vision problems: Night blindness is often the earliest sign of a vitamin A deficiency. Those affected have difficulty orientating themselves in low light conditions or see poorly in the dark [1,11].

Dry skin: Reduced production of skin oils due to the vitamin deficiency can lead to dry skin, particularly on the elbows, hands and feet [11].

Susceptibility to infections: A weakened immune system can lead to increased infections of the respiratory tract, eyes or gastrointestinal tract [11].

Hair loss: The vitamin is important for healthy hair growth. A deficiency can lead to hair loss or brittle hair [12].

Slowed growth and development: In children, a deficiency can affect growth and development, which can lead to delays in physical and mental development [11].

Increased risk of reproductive problems: Vitamin A deficiency can affect reproductive function and lead to problems such as infertility in women [5,11].

Severe vitamin A deficiency can cause serious health problems, but it is important to note that excessive vitamin A consumption can also be harmful to health. Symptoms of deficiency can vary depending on the severity and diagnosis should always be made by a doctor

Where is a lot of vitamin A found?

The vitamin is found in food in two forms: as retinol in animal foods and as a carotenoid (a vitaminoid, the precursor of vitamins) in plant foods. Here are some food sources of vitamin A to cover the daily requirement:

Animal sources: Liver is one of the richest sources of vitamin A among foods. Foods such as milk, cheese and egg yolk also contain it, albeit in smaller quantities compared to liver. Some types of fish such as salmon, mackerel and tuna also contain this vitamin, but in smaller quantities compared to liver. Eating a balanced diet that includes a variety of foods can help maintain adequate vitamin A levels.

Plant sources: It is important to note that animal foods such as liver, dairy products and egg yolk directly contain vitamin A in the form of retinol, while plant foods primarily provide precursors such as beta-carotene, which can be converted into vitamin A in the body.

Which fruit and vegetables have the most vitamin A or beta-carotene?

Different types of fruit and vegetables contain different amounts of the vitamin and its precursors, the carotenoids. Here are some plant-based foods that are particularly good sources of provitamin A or vitamin A: Sweet potatoes are an excellent food source of beta-carotene, which is converted into the vitamin by the body. One portion of sweet potatoes covers a considerable part of the daily requirement of the vitamin. Carrots are also known for their high beta-carotene content, which is also converted into retinol. Raw or cooked, carrots are a good source of vitamin A (in the form of beta-carotene). Other vegetables that are a good source: Spinach, pumpkin and kale. Among fruits, these foods are particularly rich in beta-carotene: mangoes, apricots. Cantaloupe melons and peaches.

Regularly consuming a variety of these fruits and vegetables can help prevent vitamin A deficiency, meet daily requirements and promote a balanced diet with many different foods.

Maximum amount of vitamin A per day

The German Nutrition Society (DGE) issues recommendations for the daily intake of nutrients, including the daily vitamin A requirement. The recommended intake values vary depending on age group and gender. Here are the recommended intakes for the vitamin according to the DGE recommendations [13]:

Infants (0-4 months): 400 micrograms (mcg) per day
Infants (4-12 months): 500 mcg per day
Children (1-4 years): 300 mcg per day
Children (4-7 years): 400 mcg per day
Children (7-10 years): 500 mcg per day
Adolescents (10-19 years): 700-800 mcg per day
Adults (19 years and older): 800 mcg per day for men and 700 mcg per day for women

The DGE issues these recommendations as guidelines for a balanced diet. It is important to note that individual needs may vary depending on health status, pregnancy, breastfeeding or other factors. A varied diet that includes different sources can help to achieve the recommended intake values.

How else can you support your vitamin A intake through your diet?

Proper preparation plays an important role for foods with a high beta-carotene or vitamin A content. Some preparation methods can increase the bioavailability of the vitamin. For example, cooking vegetables in fat can improve the absorption of this fat-soluble vitamin. This is because fat-soluble vitamins dissolve in fat but not in water. This has an impact on their processing and how they are transported in different tissues.

To optimise the absorption of fat-soluble vitamins such as vitamin A, it is important to consume them together with fat sources. This facilitates their absorption in the intestine and the subsequent utilisation of vitamin A in the body.

In addition, excessive alcohol consumption should be avoided, as this can lead to liver damage, which in turn can impair storage and conversion.

What should you look out for in food supplements?

When using dietary supplements, it is important to pay attention to various aspects to ensure their effectiveness and safety: Choose products from trustworthy manufacturers that offer high-quality and tested dietary supplements. Check that the products have been independently tested for purity and quality. Make sure that the ingredients of the supplements are clearly listed and that the dosage corresponds to the recommended requirements or individual needs. Consider possible interactions with medication or other food supplements. Find out whether the food supplement is compatible with other substances you are taking and consult a doctor or pharmacist if you have any concerns.

Sources:
[1] https://www.mdpi.com/1422-0067/23/3/1014
[2] https://www. ncbi.nlm.nih.gov/pmc/articles/PMC6162863/
[3] https://www.jbc.org/article/S0021-9258(18)35934-9/pdf
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6791161/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257687/
[6] https://pubmed.ncbi.nlm.nih.gov/7832047/
[7] https://pubmed.ncbi.nlm.nih.gov/10218665/
[8] https://pubmed.ncbi.nlm.nih.gov/17515510/
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574737/
[10] https://pubmed.ncbi.nlm.nih.gov/32428912/
[11] https://www.webmd. com/vitamins-and-supplements/what-is-vitamin-a-deficiency
[12] https://www.theindependentpharmacy.co.uk/hair-loss/guides/10-vitamin-deficiencies-that-are-linked-to-hair-loss
[13] https://www.dge.de/gesunde-ernaehrung/faq/ausgewaehlte-fragen-und-antworten-zu-vitamin-a/