The most important sources that keep the body and mental health together are vitamins. Among the fundamental vitamins, vitamin A is of great importance for the human body.
What is vitamin A? Where is it? What is vitamin A for? What are the causes of vitamin A deficiency and how do we recognize its symptoms? Read on for all the details.
Vitamin A makes up a variety of substances that have a similar physiological effect. It is distinguished in vitamin A₁ (retinol) and vitamin A₂ (retina). Both forms arise from the herbal precursor beta-carotene. Beta carotene belongs to the group of carotenoids and is also known as provitamin A.
Table of Contents
Discovery of vitamin A
Researchers Stepp, McCollum, and Hopkins discovered the vitamin in 1910. The research team collected experimental animals without vitamin A and found that they suffered from stunted growth and conjunctivitis.
The symptoms disappeared when the team fed the animals liver, butter and milk. German researcher Willhelm Stepp came up with the idea for this original experimental design. Three years later, the vitamin was first isolated by Elmer McCollum. Swiss chemist Paul Karrer discovered the chemical structure of vitamin A1 in 1931.
Although research on vitamin A began in the early 20th century, the use of the vitamin occurred earlier. The Chinese used liver and honey in 1500 BC. C. to cure night blindness. Even the ancient Egyptians knew that eating liver improves vision.
Science has now discovered that vitamin A performs many tasks in a person’s body. It is important for the eyes, skin, mucous membranes, growth, immune defense, and plays a role in the development of the embryo.
How is vitamin A absorbed and processed by the body?
Your body absorbs one of the two precursors of vitamin A through food. Beta carotene is found in plants and retinyl in animal sources. Both forms are converted to retinol in the intestine and liver.
After that, the liver stores retinol as a reserve substance or the retinol enters the bloodstream. Retinol is transported through the bloodstream to the target tissue. There, the enzymatic division of retinol into retinoic acid takes place, which is then actively present in cells.
The end products of metabolism are excreted by the kidney through the urine. Foods that contain vitamin A should be eaten with fat. Fat helps release the vitamin from food.
The most important functions of vitamin A
Vitamin A does a lot of work in your body. Here are the five most important tasks.
This vitamin is effective against night blindness and helps treat eye disorders, plays an active role against some types of cancer, and provides healthy skin, nails and hair.
1. Helps improve our vision
Vitamin A can help us significantly improve our vision. Vitamin A is a crucial component of the visual pigment rhodopsin. Rhodopsin is a protein and is found in the retina of the eyes. It is responsible for the light-dark adjustment and the perception of gray tones.
It acts as a light sensor and reacts to the smallest changes in light. When units of light (photons) hit the protein, it changes its shape. This sets off a series of biochemical processes that allow us to see better in the dark. In addition, vitamin A participates in the formation of intraocular fluid.
2. Intervenes in the construction and protection of the skin
Vitamin A participates in the development and protection of the skin: Vitamin A regulates the cell growth of the skin. Retinoids act on the epidermis (upper layer of the skin). Horny cells are produced there.
Vitamin A regulates the keratinization processes of the skin and is also used against acne. Retinol also plays a role in regulating sebum production and collagen formation. Collagen is found in the lower layers of the skin and ensures that the skin remains smooth.
You can also use vitamin A to fight skin aging: as an antioxidant, it captures free radicals and prevents wrinkles or age spots.
3. Vitamin A is the foundation of growth
Vitamin A can inhibit or promote cell growth. In addition, it influences cell differentiation. In cell differentiation, cells are structurally rebuilt so they can do their job.
Vitamin A especially differentiates the new cells of the skin and mucous membranes. It also plays a role in the development and formation of hair, eyes, lymphatics, gametes, teeth, and bones. One symptom of vitamin A deficiency is the formation of bone tissue in places where there are usually no bones. This is due to an erroneous differentiation of cells.
4. Improve our defenses
The action of vitamin A on the skin and mucous membranes protects us against harmful viruses. The skin and mucous membranes act as barriers, so viruses cannot enter the body at all.
Vitamin A is also involved in the formation and differentiation of white blood cells, whose main task is to defend against pathogens. Additionally, vitamin A affects regulatory T cells. These prevent excessive immune reactions and, therefore, autoimmune reactions.
5. Has an important role in reproduction
The vitamin regulates the formation of the sex hormones testosterone and estrogen. Testosterone in turn has a positive effect on the quality and number of sperm. Research on this topic revealed that vitamin A deficiency affects sperm production.
Additionally, vitamin A has a regulatory effect on embryonic development. It is involved in the formation of new cells and supports the development of the lungs. However, too much vitamin A in pregnancy can lead to malformations. Therefore, pregnant women should refrain from eating foods that contain a lot of vitamin A.
As you can see, vitamin A is involved in many biochemical processes in the body. Insufficient supply of the vitamin disturbs these processes and therefore damages health.
Causes of vitamin A deficiency
Vitamin A deficiency is seen when there are some nutritional deficiencies or a very unbalanced diet. However, vitamin A deficiency is not common, and it usually occurs more frequently in babies and women who have just given birth.
- Inadequate food intake.
- Fever, chronic infections.
- Thyroid gland affected.
- Cystic fibrosis disorder (a genetic disease that affects the external secretory glands).
- Celiac disease and Crohn’s disease can cause these deficiencies.
Symptoms and consequences of a vitamin A deficiency
While vitamin A is considered the eye vitamin, the symptoms of vitamin A deficiency are not just limited to the eyes. Nonspecific symptoms appear first, as with most symptoms of nutritional deficiencies. These include headaches, pale skin, dizziness, fatigue, and trouble concentrating.
The cause of these symptoms is anemia. In anemia, the concentration of red blood cells in the blood is too low. Vitamin A regulates the formation of red blood cells. Red blood cells carry oxygen from the lungs to the organs. If less oxygen is transported to the organs, this is reflected in performance losses.
Vitamin A deficiency weakens the immune system, interferes with bone development, and damages teeth.
1. Growth interrupted
Vitamin A deficiency can led to growth disorders in children, as the vitamin is involved in the formation and differentiation of new cells. It is also essential for building and maintaining bones and teeth. One symptom of deficiency is the formation of bone where the bones normally should not be. Additionally, a deficiency can led to disturbed or delayed lung development.
2. Night blindness and reduced vision
The most common symptom of vitamin A deficiency is night blindness. It is difficult for those affected to see at sunset. In the dark, as in the night, the affected person does not see anything at all. This is due to a lack of rhodopsin, which allows light-dark vision.
Vision is generally disturbed. The image becomes blurry and dull. Since vitamin A is important for the formation of intraocular fluid, a deficiency can cause the conjunctiva to dry out.
This dehydration due to vitamin A deficiency is called xerophthalmia. Also, there are often visible white spots, called bitot spots. Without medical treatment, blindness occurs due to fusion of the cornea (keratomalacia).
3. Promotes the development of psoriasis
Due to vitamin A deficiency, the skin becomes dry and psoriasis develops. Another symptom is hair loss. Also, a deficiency promotes the development of acne. Also, lung tissue is affected.
Cells in the mucosa rebuild into cells in the cornea, which can lead to breathing difficulties. This transformation also affects the mucous membranes of the nose and respiratory tract. This can lead to cell death (necrosis) or pneumonia.
4. Vitamin A deficiency in embryonic development
As a result of vitamin, A deficiency, embryo malformations can occur. The genitalia, gastrointestinal tract, teeth and ears of the embryo are affected.
However, these same malformations can also occur with excessive retinol consumption. Retinol is the biologically active form of vitamin A and is found only in animal products. Therefore, you should abstain from this form of vitamin during pregnancy and take vitamin A in the form of herbs. Beta-carotene can be stored in the liver until it is needed. This cannot lead to an overdose.
Spread of vitamin A deficiency
Lack of supply of vitamin A is one of the biggest dietary problems in the world. This is mainly due to the scarce supply in developing countries, whose diet is mainly based on rice.
White rice does not contain vitamin A. This often causes increased visual impairment in these countries. According to research, between 250,000 and 500,000 children go blind each year as a result of vitamin A deficiency.
Other research suggests that 2 million people die each year from vitamin A deficiency. A countermeasure is the development of a genetically modified rice, the so-called golden rice.
Shortages don’t just happen in developing countries. Even in industrialized countries it can lead to deficiency symptoms.
Who is more prone to vitamin A deficiency?
Lack of vitamin A is very dangerous for children, as they are still developing. Children also have a smaller liver and, therefore, can absorb less vitamin A. However, pregnant women, people over 65, and high-performance athletes have a greater need. These people need more vitamin A due to physical changes.
Another risk group is vegetarians, vegans or people who are on a diet. They eat less vitamin A due to their diet and should be careful to include foods containing vitamin A in their diet.
Diseases can prevent or hinder vitamin A intake. These mainly include diseases of the liver and gastrointestinal tract.
People with obesity or alcohol problems often suffer from liver problems (fatty liver, liver cirrhosis). This makes it difficult to take vitamin A.
How to reverse vitamin A deficiency?
Lack of vitamin A is rare in industrialized countries. But once it is a deficiency, it can be dangerous. Therefore, it is important to prevent a deficiency.
Prevention with the right diet.
A varied diet is the basis for preventing many diseases. However, vitamin A is not included in all foods. Especially vegetarians and vegans should pay attention to their diet.
The following foods contain a lot of vitamin A:
- Vegetables: carrots, kale, broccoli, sweet potatoes, arugula, spinach, chicory.
- Fruits: melon, watermelon, cherries, apricots, mango, papaya
- Animal products: cod liver oil, liver, egg, mackerel, tuna, poultry.
The bioavailability of vitamin A increases with the addition of fat. Bioavailability refers to the body’s ability to absorb and process a particular nutrient. Some foods naturally contain fat, which ensures bioavailability.
Other foods, especially fruits and vegetables, are fat-free. Therefore, you should always add some fat, such as oil, in the preparation. It is also important that the food is well mashed. The bioavailability of vitamin A from chopped carrots is about five percent.
Supplements in case of existing deficiency
Taking vitamin, A supplements can prevent a deficiency or make up for an existing deficiency. For very serious symptoms such as night blindness, you should definitely see a doctor to rule out other conditions. Also, it is important to find the cause of vitamin A deficiency.
Most vitamin A supplements are in capsule form. You can take the capsules with you during a meal.
There are beta-carotene capsules and retinol capsules. Beta-carotene has the advantage that it cannot cause an overdose. The body does not convert excess beta-carotene into vitamin A, but stores it in the liver.